# List(Of T) Class

**Visual Studio 2010**

Represents a strongly typed list of objects that can be accessed by index. Provides methods to search, sort, and manipulate lists.

**Namespace:**System.Collections.Generic

**Assembly:**mscorlib (in mscorlib.dll)

The List(Of T) type exposes the following members.

Name | Description | |
---|---|---|

List(Of T) | Initializes a new instance of the List(Of T) class that is empty and has the default initial capacity. | |

List(Of T)(IEnumerable(Of T)) | Initializes a new instance of the List(Of T) class that contains elements copied from the specified collection and has sufficient capacity to accommodate the number of elements copied. | |

List(Of T)(Int32) | Initializes a new instance of the List(Of T) class that is empty and has the specified initial capacity. |

Name | Description | |
---|---|---|

Add | Adds an object to the end of the List(Of T). | |

AddRange | Adds the elements of the specified collection to the end of the List(Of T). | |

AsReadOnly | Returns a read-only IList(Of T) wrapper for the current collection. | |

BinarySearch(T) | Searches the entire sorted List(Of T) for an element using the default comparer and returns the zero-based index of the element. | |

BinarySearch(T, IComparer(Of T)) | Searches the entire sorted List(Of T) for an element using the specified comparer and returns the zero-based index of the element. | |

BinarySearch(Int32, Int32, T, IComparer(Of T)) | Searches a range of elements in the sorted List(Of T) for an element using the specified comparer and returns the zero-based index of the element. | |

Clear | Removes all elements from the List(Of T). | |

Contains | Determines whether an element is in the List(Of T). | |

ConvertAll(Of TOutput) | Converts the elements in the current List(Of T) to another type, and returns a list containing the converted elements. | |

CopyTo(T()) | Copies the entire List(Of T) to a compatible one-dimensional array, starting at the beginning of the target array. | |

CopyTo(T(), Int32) | Copies the entire List(Of T) to a compatible one-dimensional array, starting at the specified index of the target array. | |

CopyTo(Int32, T(), Int32, Int32) | Copies a range of elements from the List(Of T) to a compatible one-dimensional array, starting at the specified index of the target array. | |

Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) | |

Exists | Determines whether the List(Of T) contains elements that match the conditions defined by the specified predicate. | |

Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) | |

Find | Searches for an element that matches the conditions defined by the specified predicate, and returns the first occurrence within the entire List(Of T). | |

FindAll | Retrieves all the elements that match the conditions defined by the specified predicate. | |

FindIndex(Predicate(Of T)) | Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the first occurrence within the entire List(Of T). | |

FindIndex(Int32, Predicate(Of T)) | Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the first occurrence within the range of elements in the List(Of T) that extends from the specified index to the last element. | |

FindIndex(Int32, Int32, Predicate(Of T)) | Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the first occurrence within the range of elements in the List(Of T) that starts at the specified index and contains the specified number of elements. | |

FindLast | Searches for an element that matches the conditions defined by the specified predicate, and returns the last occurrence within the entire List(Of T). | |

FindLastIndex(Predicate(Of T)) | Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the entire List(Of T). | |

FindLastIndex(Int32, Predicate(Of T)) | Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the List(Of T) that extends from the first element to the specified index. | |

FindLastIndex(Int32, Int32, Predicate(Of T)) | Searches for an element that matches the conditions defined by the specified predicate, and returns the zero-based index of the last occurrence within the range of elements in the List(Of T) that contains the specified number of elements and ends at the specified index. | |

ForEach | Performs the specified action on each element of the List(Of T). | |

GetEnumerator | Returns an enumerator that iterates through the List(Of T). | |

GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) | |

GetRange | Creates a shallow copy of a range of elements in the source List(Of T). | |

GetType | Gets the Type of the current instance. (Inherited from Object.) | |

IndexOf(T) | Searches for the specified object and returns the zero-based index of the first occurrence within the entire List(Of T). | |

IndexOf(T, Int32) | Searches for the specified object and returns the zero-based index of the first occurrence within the range of elements in the List(Of T) that extends from the specified index to the last element. | |

IndexOf(T, Int32, Int32) | Searches for the specified object and returns the zero-based index of the first occurrence within the range of elements in the List(Of T) that starts at the specified index and contains the specified number of elements. | |

Insert | Inserts an element into the List(Of T) at the specified index. | |

InsertRange | Inserts the elements of a collection into the List(Of T) at the specified index. | |

LastIndexOf(T) | Searches for the specified object and returns the zero-based index of the last occurrence within the entire List(Of T). | |

LastIndexOf(T, Int32) | Searches for the specified object and returns the zero-based index of the last occurrence within the range of elements in the List(Of T) that extends from the first element to the specified index. | |

LastIndexOf(T, Int32, Int32) | Searches for the specified object and returns the zero-based index of the last occurrence within the range of elements in the List(Of T) that contains the specified number of elements and ends at the specified index. | |

MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) | |

Remove | Removes the first occurrence of a specific object from the List(Of T). | |

RemoveAll | Removes all the elements that match the conditions defined by the specified predicate. | |

RemoveAt | Removes the element at the specified index of the List(Of T). | |

RemoveRange | Removes a range of elements from the List(Of T). | |

Reverse | Reverses the order of the elements in the entire List(Of T). | |

Reverse(Int32, Int32) | Reverses the order of the elements in the specified range. | |

Sort | Sorts the elements in the entire List(Of T) using the default comparer. | |

Sort(Comparison(Of T)) | Sorts the elements in the entire List(Of T) using the specified System.Comparison(Of T). | |

Sort(IComparer(Of T)) | Sorts the elements in the entire List(Of T) using the specified comparer. | |

Sort(Int32, Int32, IComparer(Of T)) | Sorts the elements in a range of elements in List(Of T) using the specified comparer. | |

ToArray | Copies the elements of the List(Of T) to a new array. | |

ToString | Returns a string that represents the current object. (Inherited from Object.) | |

TrimExcess | Sets the capacity to the actual number of elements in the List(Of T), if that number is less than a threshold value. | |

TrueForAll | Determines whether every element in the List(Of T) matches the conditions defined by the specified predicate. |

Name | Description | |
---|---|---|

Aggregate(Of T)(Func(Of T, T, T)) | Overloaded. Applies an accumulator function over a sequence. (Defined by Enumerable.) | |

Aggregate(Of T, TAccumulate)(TAccumulate, Func(Of TAccumulate, T, TAccumulate)) | Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value. (Defined by Enumerable.) | |

Aggregate(Of T, TAccumulate, TResult)(TAccumulate, Func(Of TAccumulate, T, TAccumulate), Func(Of TAccumulate, TResult)) | Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value. (Defined by Enumerable.) | |

All(Of T) | Determines whether all elements of a sequence satisfy a condition. (Defined by Enumerable.) | |

Any(Of T) | Overloaded. Determines whether a sequence contains any elements. (Defined by Enumerable.) | |

Any(Of T)(Func(Of T, Boolean)) | Overloaded. Determines whether any element of a sequence satisfies a condition. (Defined by Enumerable.) | |

AsEnumerable(Of T) | Returns the input typed as IEnumerable(Of T). (Defined by Enumerable.) | |

AsParallel | Overloaded. Enables parallelization of a query. (Defined by ParallelEnumerable.) | |

AsParallel(Of T) | Overloaded. Enables parallelization of a query. (Defined by ParallelEnumerable.) | |

AsQueryable | Overloaded. Converts an IEnumerable to an IQueryable. (Defined by Queryable.) | |

AsQueryable(Of T) | Overloaded. Converts a generic IEnumerable(Of T) to a generic IQueryable(Of T). (Defined by Queryable.) | |

Average(Of T)(Func(Of T, Decimal)) | Overloaded. Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Average(Of T)(Func(Of T, Nullable(Of Decimal))) | Overloaded. Computes the average of a sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Average(Of T)(Func(Of T, Double)) | Overloaded. Computes the average of a sequence of Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Average(Of T)(Func(Of T, Nullable(Of Double))) | Overloaded. Computes the average of a sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Average(Of T)(Func(Of T, Int32)) | Overloaded. Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Average(Of T)(Func(Of T, Nullable(Of Int32))) | Overloaded. Computes the average of a sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Average(Of T)(Func(Of T, Int64)) | Overloaded. Computes the average of a sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Average(Of T)(Func(Of T, Nullable(Of Int64))) | Overloaded. Computes the average of a sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Average(Of T)(Func(Of T, Single)) | Overloaded. Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Average(Of T)(Func(Of T, Nullable(Of Single))) | Overloaded. Computes the average of a sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Cast(Of TResult) | Casts the elements of an IEnumerable to the specified type. (Defined by Enumerable.) | |

Concat(Of T) | Concatenates two sequences. (Defined by Enumerable.) | |

Contains(Of T)(T) | Overloaded. Determines whether a sequence contains a specified element by using the default equality comparer. (Defined by Enumerable.) | |

Contains(Of T)(T, IEqualityComparer(Of T)) | Overloaded. Determines whether a sequence contains a specified element by using a specified IEqualityComparer(Of T). (Defined by Enumerable.) | |

Count(Of T) | Overloaded. Returns the number of elements in a sequence. (Defined by Enumerable.) | |

Count(Of T)(Func(Of T, Boolean)) | Overloaded. Returns a number that represents how many elements in the specified sequence satisfy a condition. (Defined by Enumerable.) | |

DefaultIfEmpty(Of T) | Overloaded. Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty. (Defined by Enumerable.) | |

DefaultIfEmpty(Of T)(T) | Overloaded. Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty. (Defined by Enumerable.) | |

Distinct(Of T) | Overloaded. Returns distinct elements from a sequence by using the default equality comparer to compare values. (Defined by Enumerable.) | |

Distinct(Of T)(IEqualityComparer(Of T)) | Overloaded. Returns distinct elements from a sequence by using a specified IEqualityComparer(Of T) to compare values. (Defined by Enumerable.) | |

ElementAt(Of T) | Returns the element at a specified index in a sequence. (Defined by Enumerable.) | |

ElementAtOrDefault(Of T) | Returns the element at a specified index in a sequence or a default value if the index is out of range. (Defined by Enumerable.) | |

Except(Of T)(IEnumerable(Of T)) | Overloaded. Produces the set difference of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.) | |

Except(Of T)(IEnumerable(Of T), IEqualityComparer(Of T)) | Overloaded. Produces the set difference of two sequences by using the specified IEqualityComparer(Of T) to compare values. (Defined by Enumerable.) | |

First(Of T) | Overloaded. Returns the first element of a sequence. (Defined by Enumerable.) | |

First(Of T)(Func(Of T, Boolean)) | Overloaded. Returns the first element in a sequence that satisfies a specified condition. (Defined by Enumerable.) | |

FirstOrDefault(Of T) | Overloaded. Returns the first element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.) | |

FirstOrDefault(Of T)(Func(Of T, Boolean)) | Overloaded. Returns the first element of the sequence that satisfies a condition or a default value if no such element is found. (Defined by Enumerable.) | |

GroupBy(Of T, TKey)(Func(Of T, TKey)) | Overloaded. Groups the elements of a sequence according to a specified key selector function. (Defined by Enumerable.) | |

GroupBy(Of T, TKey)(Func(Of T, TKey), IEqualityComparer(Of TKey)) | Overloaded. Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer. (Defined by Enumerable.) | |

GroupBy(Of T, TKey, TElement)(Func(Of T, TKey), Func(Of T, TElement)) | Overloaded. Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function. (Defined by Enumerable.) | |

GroupBy(Of T, TKey, TResult)(Func(Of T, TKey), Func(Of TKey, IEnumerable(Of T), TResult)) | Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. (Defined by Enumerable.) | |

GroupBy(Of T, TKey, TElement)(Func(Of T, TKey), Func(Of T, TElement), IEqualityComparer(Of TKey)) | Overloaded. Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function. (Defined by Enumerable.) | |

GroupBy(Of T, TKey, TResult)(Func(Of T, TKey), Func(Of TKey, IEnumerable(Of T), TResult), IEqualityComparer(Of TKey)) | Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer. (Defined by Enumerable.) | |

GroupBy(Of T, TKey, TElement, TResult)(Func(Of T, TKey), Func(Of T, TElement), Func(Of TKey, IEnumerable(Of TElement), TResult)) | Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function. (Defined by Enumerable.) | |

GroupBy(Of T, TKey, TElement, TResult)(Func(Of T, TKey), Func(Of T, TElement), Func(Of TKey, IEnumerable(Of TElement), TResult), IEqualityComparer(Of TKey)) | Overloaded. Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function. (Defined by Enumerable.) | |

GroupJoin(Of T, TInner, TKey, TResult)(IEnumerable(Of TInner), Func(Of T, TKey), Func(Of TInner, TKey), Func(Of T, IEnumerable(Of TInner), TResult)) | Overloaded. Correlates the elements of two sequences based on equality of keys and groups the results. The default equality comparer is used to compare keys. (Defined by Enumerable.) | |

GroupJoin(Of T, TInner, TKey, TResult)(IEnumerable(Of TInner), Func(Of T, TKey), Func(Of TInner, TKey), Func(Of T, IEnumerable(Of TInner), TResult), IEqualityComparer(Of TKey)) | Overloaded. Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer(Of T) is used to compare keys. (Defined by Enumerable.) | |

Intersect(Of T)(IEnumerable(Of T)) | Overloaded. Produces the set intersection of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.) | |

Intersect(Of T)(IEnumerable(Of T), IEqualityComparer(Of T)) | Overloaded. Produces the set intersection of two sequences by using the specified IEqualityComparer(Of T) to compare values. (Defined by Enumerable.) | |

Join(Of T, TInner, TKey, TResult)(IEnumerable(Of TInner), Func(Of T, TKey), Func(Of TInner, TKey), Func(Of T, TInner, TResult)) | Overloaded. Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys. (Defined by Enumerable.) | |

Join(Of T, TInner, TKey, TResult)(IEnumerable(Of TInner), Func(Of T, TKey), Func(Of TInner, TKey), Func(Of T, TInner, TResult), IEqualityComparer(Of TKey)) | Overloaded. Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer(Of T) is used to compare keys. (Defined by Enumerable.) | |

Last(Of T) | Overloaded. Returns the last element of a sequence. (Defined by Enumerable.) | |

Last(Of T)(Func(Of T, Boolean)) | Overloaded. Returns the last element of a sequence that satisfies a specified condition. (Defined by Enumerable.) | |

LastOrDefault(Of T) | Overloaded. Returns the last element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.) | |

LastOrDefault(Of T)(Func(Of T, Boolean)) | Overloaded. Returns the last element of a sequence that satisfies a condition or a default value if no such element is found. (Defined by Enumerable.) | |

LongCount(Of T) | Overloaded. Returns an Int64 that represents the total number of elements in a sequence. (Defined by Enumerable.) | |

LongCount(Of T)(Func(Of T, Boolean)) | Overloaded. Returns an Int64 that represents how many elements in a sequence satisfy a condition. (Defined by Enumerable.) | |

Max(Of T) | Overloaded. Returns the maximum value in a generic sequence. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Decimal)) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Decimal value. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Nullable(Of Decimal))) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Double)) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Double value. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Nullable(Of Double))) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Double value. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Int32)) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int32 value. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Nullable(Of Int32))) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Int64)) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int64 value. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Nullable(Of Int64))) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Single)) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Single value. (Defined by Enumerable.) | |

Max(Of T)(Func(Of T, Nullable(Of Single))) | Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Single value. (Defined by Enumerable.) | |

Max(Of T, TResult)(Func(Of T, TResult)) | Overloaded. Invokes a transform function on each element of a generic sequence and returns the maximum resulting value. (Defined by Enumerable.) | |

Min(Of T) | Overloaded. Returns the minimum value in a generic sequence. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Decimal)) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Decimal value. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Nullable(Of Decimal))) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Double)) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Double value. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Nullable(Of Double))) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Double value. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Int32)) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int32 value. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Nullable(Of Int32))) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Int64)) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int64 value. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Nullable(Of Int64))) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Single)) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Single value. (Defined by Enumerable.) | |

Min(Of T)(Func(Of T, Nullable(Of Single))) | Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Single value. (Defined by Enumerable.) | |

Min(Of T, TResult)(Func(Of T, TResult)) | Overloaded. Invokes a transform function on each element of a generic sequence and returns the minimum resulting value. (Defined by Enumerable.) | |

OfType(Of TResult) | Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.) | |

OrderBy(Of T, TKey)(Func(Of T, TKey)) | Overloaded. Sorts the elements of a sequence in ascending order according to a key. (Defined by Enumerable.) | |

OrderBy(Of T, TKey)(Func(Of T, TKey), IComparer(Of TKey)) | Overloaded. Sorts the elements of a sequence in ascending order by using a specified comparer. (Defined by Enumerable.) | |

OrderByDescending(Of T, TKey)(Func(Of T, TKey)) | Overloaded. Sorts the elements of a sequence in descending order according to a key. (Defined by Enumerable.) | |

OrderByDescending(Of T, TKey)(Func(Of T, TKey), IComparer(Of TKey)) | Overloaded. Sorts the elements of a sequence in descending order by using a specified comparer. (Defined by Enumerable.) | |

Reverse(Of T) | Inverts the order of the elements in a sequence. (Defined by Enumerable.) | |

Select(Of T, TResult)(Func(Of T, TResult)) | Overloaded. Projects each element of a sequence into a new form. (Defined by Enumerable.) | |

Select(Of T, TResult)(Func(Of T, Int32, TResult)) | Overloaded. Projects each element of a sequence into a new form by incorporating the element's index. (Defined by Enumerable.) | |

SelectMany(Of T, TResult)(Func(Of T, IEnumerable(Of TResult))) | Overloaded. Projects each element of a sequence to an IEnumerable(Of T) and flattens the resulting sequences into one sequence. (Defined by Enumerable.) | |

SelectMany(Of T, TResult)(Func(Of T, Int32, IEnumerable(Of TResult))) | Overloaded. Projects each element of a sequence to an IEnumerable(Of T), and flattens the resulting sequences into one sequence. The index of each source element is used in the projected form of that element. (Defined by Enumerable.) | |

SelectMany(Of T, TCollection, TResult)(Func(Of T, Int32, IEnumerable(Of TCollection)), Func(Of T, TCollection, TResult)) | Overloaded. Projects each element of a sequence to an IEnumerable(Of T), flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. The index of each source element is used in the intermediate projected form of that element. (Defined by Enumerable.) | |

SelectMany(Of T, TCollection, TResult)(Func(Of T, IEnumerable(Of TCollection)), Func(Of T, TCollection, TResult)) | Overloaded. Projects each element of a sequence to an IEnumerable(Of T), flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. (Defined by Enumerable.) | |

SequenceEqual(Of T)(IEnumerable(Of T)) | Overloaded. Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type. (Defined by Enumerable.) | |

SequenceEqual(Of T)(IEnumerable(Of T), IEqualityComparer(Of T)) | Overloaded. Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer(Of T). (Defined by Enumerable.) | |

Single(Of T) | Overloaded. Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence. (Defined by Enumerable.) | |

Single(Of T)(Func(Of T, Boolean)) | Overloaded. Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists. (Defined by Enumerable.) | |

SingleOrDefault(Of T) | Overloaded. Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence. (Defined by Enumerable.) | |

SingleOrDefault(Of T)(Func(Of T, Boolean)) | Overloaded. Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition. (Defined by Enumerable.) | |

Skip(Of T) | Bypasses a specified number of elements in a sequence and then returns the remaining elements. (Defined by Enumerable.) | |

SkipWhile(Of T)(Func(Of T, Boolean)) | Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. (Defined by Enumerable.) | |

SkipWhile(Of T)(Func(Of T, Int32, Boolean)) | Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Decimal)) | Overloaded. Computes the sum of the sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Nullable(Of Decimal))) | Overloaded. Computes the sum of the sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Double)) | Overloaded. Computes the sum of the sequence of Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Nullable(Of Double))) | Overloaded. Computes the sum of the sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Int32)) | Overloaded. Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Nullable(Of Int32))) | Overloaded. Computes the sum of the sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Int64)) | Overloaded. Computes the sum of the sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Nullable(Of Int64))) | Overloaded. Computes the sum of the sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Single)) | Overloaded. Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Sum(Of T)(Func(Of T, Nullable(Of Single))) | Overloaded. Computes the sum of the sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence. (Defined by Enumerable.) | |

Take(Of T) | Returns a specified number of contiguous elements from the start of a sequence. (Defined by Enumerable.) | |

TakeWhile(Of T)(Func(Of T, Boolean)) | Overloaded. Returns elements from a sequence as long as a specified condition is true. (Defined by Enumerable.) | |

TakeWhile(Of T)(Func(Of T, Int32, Boolean)) | Overloaded. Returns elements from a sequence as long as a specified condition is true. The element's index is used in the logic of the predicate function. (Defined by Enumerable.) | |

ToArray(Of T) | Creates an array from a IEnumerable(Of T). (Defined by Enumerable.) | |

ToDictionary(Of T, TKey)(Func(Of T, TKey)) | Overloaded. Creates a Dictionary(Of TKey, TValue) from an IEnumerable(Of T) according to a specified key selector function. (Defined by Enumerable.) | |

ToDictionary(Of T, TKey)(Func(Of T, TKey), IEqualityComparer(Of TKey)) | Overloaded. Creates a Dictionary(Of TKey, TValue) from an IEnumerable(Of T) according to a specified key selector function and key comparer. (Defined by Enumerable.) | |

ToDictionary(Of T, TKey, TElement)(Func(Of T, TKey), Func(Of T, TElement)) | Overloaded. Creates a Dictionary(Of TKey, TValue) from an IEnumerable(Of T) according to specified key selector and element selector functions. (Defined by Enumerable.) | |

ToDictionary(Of T, TKey, TElement)(Func(Of T, TKey), Func(Of T, TElement), IEqualityComparer(Of TKey)) | Overloaded. Creates a Dictionary(Of TKey, TValue) from an IEnumerable(Of T) according to a specified key selector function, a comparer, and an element selector function. (Defined by Enumerable.) | |

ToList(Of T) | Creates a List(Of T) from an IEnumerable(Of T). (Defined by Enumerable.) | |

ToLookup(Of T, TKey)(Func(Of T, TKey)) | Overloaded. Creates a Lookup(Of TKey, TElement) from an IEnumerable(Of T) according to a specified key selector function. (Defined by Enumerable.) | |

ToLookup(Of T, TKey)(Func(Of T, TKey), IEqualityComparer(Of TKey)) | Overloaded. Creates a Lookup(Of TKey, TElement) from an IEnumerable(Of T) according to a specified key selector function and key comparer. (Defined by Enumerable.) | |

ToLookup(Of T, TKey, TElement)(Func(Of T, TKey), Func(Of T, TElement)) | Overloaded. Creates a Lookup(Of TKey, TElement) from an IEnumerable(Of T) according to specified key selector and element selector functions. (Defined by Enumerable.) | |

ToLookup(Of T, TKey, TElement)(Func(Of T, TKey), Func(Of T, TElement), IEqualityComparer(Of TKey)) | Overloaded. Creates a Lookup(Of TKey, TElement) from an IEnumerable(Of T) according to a specified key selector function, a comparer and an element selector function. (Defined by Enumerable.) | |

Union(Of T)(IEnumerable(Of T)) | Overloaded. Produces the set union of two sequences by using the default equality comparer. (Defined by Enumerable.) | |

Union(Of T)(IEnumerable(Of T), IEqualityComparer(Of T)) | Overloaded. Produces the set union of two sequences by using a specified IEqualityComparer(Of T). (Defined by Enumerable.) | |

Where(Of T)(Func(Of T, Boolean)) | Overloaded. Filters a sequence of values based on a predicate. (Defined by Enumerable.) | |

Where(Of T)(Func(Of T, Int32, Boolean)) | Overloaded. Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function. (Defined by Enumerable.) | |

Zip(Of T, TSecond, TResult) | Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results. (Defined by Enumerable.) |

Name | Description | |
---|---|---|

ICollection.CopyTo | Copies the elements of the ICollection to an Array, starting at a particular Array index. | |

ICollection(Of T).IsReadOnly | Gets a value indicating whether the ICollection(Of T) is read-only. | |

ICollection.IsSynchronized | Gets a value indicating whether access to the ICollection is synchronized (thread safe). | |

ICollection.SyncRoot | Gets an object that can be used to synchronize access to the ICollection. | |

IEnumerable(Of T).GetEnumerator | Returns an enumerator that iterates through a collection. | |

IEnumerable.GetEnumerator | Returns an enumerator that iterates through a collection. | |

IList.Add | Adds an item to the IList. | |

IList.Contains | Determines whether the IList contains a specific value. | |

IList.IndexOf | Determines the index of a specific item in the IList. | |

IList.Insert | Inserts an item to the IList at the specified index. | |

IList.IsFixedSize | Gets a value indicating whether the IList has a fixed size. | |

IList.IsReadOnly | Gets a value indicating whether the IList is read-only. | |

IList.Item | Gets or sets the element at the specified index. | |

IList.Remove | Removes the first occurrence of a specific object from the IList. |

The List(Of T) class is the generic equivalent of the ArrayList class. It implements the IList(Of T) generic interface using an array whose size is dynamically increased as required.

The List(Of T) class uses both an equality comparer and an ordering comparer.

Methods such as Contains, IndexOf, LastIndexOf, and Remove use an equality comparer for the list elements. The default equality comparer for type T is determined as follows. If type T implements the IEquatable(Of T) generic interface, then the equality comparer is the Equals(T) method of that interface; otherwise, the default equality comparer is Object.Equals(Object).

Methods such as BinarySearch and Sort use an ordering comparer for the list elements. The default comparer for type T is determined as follows. If type T implements the IComparable(Of T) generic interface, then the default comparer is the CompareTo(T) method of that interface; otherwise, if type T implements the nongeneric IComparable interface, then the default comparer is the CompareTo(Object) method of that interface. If type T implements neither interface, then there is no default comparer, and a comparer or comparison delegate must be provided explicitly.

The List(Of T) is not guaranteed to be sorted. You must sort the List(Of T) before performing operations (such as BinarySearch) that require the List(Of T) to be sorted.

Elements in this collection can be accessed using an integer index. Indexes in this collection are zero-based.

List(Of T) accepts Nothing as a valid value for reference types and allows duplicate elements.

### Performance Considerations

In deciding whether to use the List(Of T) or ArrayList class, both of which have similar functionality, remember that the List(Of T) class performs better in most cases and is type safe. If a reference type is used for type T of the List(Of T) class, the behavior of the two classes is identical. However, if a value type is used for type T, you need to consider implementation and boxing issues.

If a value type is used for type T, the compiler generates an implementation of the List(Of T) class specifically for that value type. That means a list element of a List(Of T) object does not have to be boxed before the element can be used, and after about 500 list elements are created the memory saved not boxing list elements is greater than the memory used to generate the class implementation.

Make certain the value type used for type T implements the IEquatable(Of T) generic interface. If not, methods such as Contains must call the Object.Equals(Object) method, which boxes the affected list element. If the value type implements the IComparable interface and you own the source code, also implement the IComparable(Of T) generic interface to prevent the BinarySearch and Sort methods from boxing list elements. If you do not own the source code, pass an IComparer(Of T) object to the BinarySearch and Sort methods

It is to your advantage to use the type-specific implementation of the List(Of T) class instead of using the ArrayList class or writing a strongly typed wrapper collection yourself. The reason is your implementation must do what the .NET Framework does for you already, and the common language runtime can share Microsoft intermediate language code and metadata, which your implementation cannot.

The following code example demonstrates several properties and methods of the List(Of T) generic class of type string. (For an example of a List(Of T) of complex types, see the Contains method.)

The default constructor is used to create a list of strings with the default capacity. The Capacity property is displayed and then the Add method is used to add several items. The items are listed, and the Capacity property is displayed again, along with the Count property, to show that the capacity has been increased as needed.

The Contains method is used to test for the presence of an item in the list, the Insert method is used to insert a new item in the middle of the list, and the contents of the list are displayed again.

The default Item property (the indexer in C#) is used to retrieve an item, the Remove method is used to remove the first instance of the duplicate item added earlier, and the contents are displayed again. The Remove method always removes the first instance it encounters.

The TrimExcess method is used to reduce the capacity to match the count, and the Capacity and Count properties are displayed. If the unused capacity had been less than 10 percent of total capacity, the list would not have been resized.

Finally, the Clear method is used to remove all items from the list, and the Capacity and Count properties are displayed.

Imports System Imports System.Collections.Generic Public Class Example Public Shared Sub Main() Dim dinosaurs As New List(Of String) Console.WriteLine(vbLf & "Capacity: {0}", dinosaurs.Capacity) dinosaurs.Add("Tyrannosaurus") dinosaurs.Add("Amargasaurus") dinosaurs.Add("Mamenchisaurus") dinosaurs.Add("Deinonychus") dinosaurs.Add("Compsognathus") Console.WriteLine() For Each dinosaur As String In dinosaurs Console.WriteLine(dinosaur) Next Console.WriteLine(vbLf & "Capacity: {0}", dinosaurs.Capacity) Console.WriteLine("Count: {0}", dinosaurs.Count) Console.WriteLine(vbLf & "Contains(""Deinonychus""): {0}", _ dinosaurs.Contains("Deinonychus")) Console.WriteLine(vbLf & "Insert(2, ""Compsognathus"")") dinosaurs.Insert(2, "Compsognathus") Console.WriteLine() For Each dinosaur As String In dinosaurs Console.WriteLine(dinosaur) Next Console.WriteLine(vbLf & "dinosaurs(3): {0}", dinosaurs(3)) Console.WriteLine(vbLf & "Remove(""Compsognathus"")") dinosaurs.Remove("Compsognathus") Console.WriteLine() For Each dinosaur As String In dinosaurs Console.WriteLine(dinosaur) Next dinosaurs.TrimExcess() Console.WriteLine(vbLf & "TrimExcess()") Console.WriteLine("Capacity: {0}", dinosaurs.Capacity) Console.WriteLine("Count: {0}", dinosaurs.Count) dinosaurs.Clear() Console.WriteLine(vbLf & "Clear()") Console.WriteLine("Capacity: {0}", dinosaurs.Capacity) Console.WriteLine("Count: {0}", dinosaurs.Count) End Sub End Class ' This code example produces the following output: ' 'Capacity: 0 ' 'Tyrannosaurus 'Amargasaurus 'Mamenchisaurus 'Deinonychus 'Compsognathus ' 'Capacity: 8 'Count: 5 ' 'Contains("Deinonychus"): True ' 'Insert(2, "Compsognathus") ' 'Tyrannosaurus 'Amargasaurus 'Compsognathus 'Mamenchisaurus 'Deinonychus 'Compsognathus ' 'dinosaurs(3): Mamenchisaurus ' 'Remove("Compsognathus") ' 'Tyrannosaurus 'Amargasaurus 'Mamenchisaurus 'Deinonychus 'Compsognathus ' 'TrimExcess() 'Capacity: 5 'Count: 5 ' 'Clear() 'Capacity: 5 'Count: 0

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

A List(Of T) can support multiple readers concurrently, as long as the collection is not modified. Enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with one or more write accesses, the only way to ensure thread safety is to lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.

System.Collections.Generic.List(Of T)

System.Data.Services.ExpandSegmentCollection

System.Workflow.Activities.OperationParameterInfoCollection

System.Workflow.Activities.WorkflowRoleCollection

System.Workflow.ComponentModel.ActivityCollection

System.Workflow.ComponentModel.Design.ActivityDesignerGlyphCollection

System.Workflow.Runtime.Tracking.ActivityTrackingLocationCollection

System.Workflow.Runtime.Tracking.ActivityTrackPointCollection

System.Workflow.Runtime.Tracking.ExtractCollection

System.Workflow.Runtime.Tracking.TrackingAnnotationCollection

System.Workflow.Runtime.Tracking.TrackingConditionCollection

System.Workflow.Runtime.Tracking.UserTrackingLocationCollection

System.Workflow.Runtime.Tracking.UserTrackPointCollection

System.Workflow.Runtime.Tracking.WorkflowTrackPointCollection