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Provides a set of **static** (**Shared** in Visual Basic) methods for querying objects that implement
IEnumerable.

**Namespace:**System.Linq

**Assembly:**System.Core (in System.Core.dll)

`public static class Enumerable`

```
[ExtensionAttribute]
public ref class Enumerable abstract sealed
```

```
[<AbstractClass>]
[<Sealed>]
type Enumerable = class end
```

```
<ExtensionAttribute>
Public NotInheritable Class Enumerable
```

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

Aggregate | Applies an accumulator function over a sequence. | |

Aggregate | Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value. | |

Aggregate | 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. | |

All | Determines whether all elements of a sequence satisfy a condition. | |

Any | Determines whether a sequence contains any elements. | |

Any | Determines whether any element of a sequence satisfies a condition. | |

Append | Appends a value to the end of the sequence. | |

AsEnumerable | Returns the input typed as IEnumerable. | |

Average | Computes the average of a sequence of Decimal values. | |

Average | Computes the average of a sequence of Double values. | |

Average | Computes the average of a sequence of Int32 values. | |

Average | Computes the average of a sequence of Int64 values. | |

Average | Computes the average of a sequence of nullable Decimal values. | |

Average | Computes the average of a sequence of nullable Double values. | |

Average | Computes the average of a sequence of nullable Int32 values. | |

Average | Computes the average of a sequence of nullable Int64 values. | |

Average | Computes the average of a sequence of nullable Single values. | |

Average | Computes the average of a sequence of Single values. | |

Average | Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence. | |

Average | Computes the average of a sequence of Double values that are obtained by invoking a transform function on each element of the input sequence. | |

Average | Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence. | |

Average | Computes the average of a sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence. | |

Average | 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. | |

Average | 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. | |

Average | 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. | |

Average | 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. | |

Average | 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. | |

Average | Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. | |

Cast | Casts the elements of an IEnumerable to the specified type. | |

Concat | Concatenates two sequences. | |

Contains | Determines whether a sequence contains a specified element by using the default equality comparer. | |

Contains | Determines whether a sequence contains a specified element by using a specified IEqualityComparer. | |

Count | Returns the number of elements in a sequence. | |

Count | Returns a number that represents how many elements in the specified sequence satisfy a condition. | |

DefaultIfEmpty | Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty. | |

DefaultIfEmpty | Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty. | |

Distinct | Returns distinct elements from a sequence by using the default equality comparer to compare values. | |

Distinct | Returns distinct elements from a sequence by using a specified IEqualityComparer to compare values. | |

ElementAt | Returns the element at a specified index in a sequence. | |

ElementAtOrDefault | Returns the element at a specified index in a sequence or a default value if the index is out of range. | |

Empty | Returns an empty IEnumerable that has the specified type argument. | |

Except | Produces the set difference of two sequences by using the default equality comparer to compare values. | |

Except | Produces the set difference of two sequences by using the specified IEqualityComparer to compare values. | |

First | Returns the first element of a sequence. | |

First | Returns the first element in a sequence that satisfies a specified condition. | |

FirstOrDefault | Returns the first element of a sequence, or a default value if the sequence contains no elements. | |

FirstOrDefault | Returns the first element of the sequence that satisfies a condition or a default value if no such element is found. | |

GroupBy | Groups the elements of a sequence according to a specified key selector function. | |

GroupBy | Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer. | |

GroupBy | 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. | |

GroupBy | 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. | |

GroupBy | Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. | |

GroupBy | 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. | |

GroupBy | 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. | |

GroupBy | 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. | |

GroupJoin | Correlates the elements of two sequences based on equality of keys and groups the results. The default equality comparer is used to compare keys. | |

GroupJoin | Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer is used to compare keys. | |

Intersect | Produces the set intersection of two sequences by using the default equality comparer to compare values. | |

Intersect | Produces the set intersection of two sequences by using the specified IEqualityComparer to compare values. | |

Join | Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys. | |

Join | Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer is used to compare keys. | |

Last | Returns the last element of a sequence. | |

Last | Returns the last element of a sequence that satisfies a specified condition. | |

LastOrDefault | Returns the last element of a sequence, or a default value if the sequence contains no elements. | |

LastOrDefault | Returns the last element of a sequence that satisfies a condition or a default value if no such element is found. | |

LongCount | Returns an Int64 that represents the total number of elements in a sequence. | |

LongCount | Returns an Int64 that represents how many elements in a sequence satisfy a condition. | |

Max | Returns the maximum value in a sequence of Decimal values. | |

Max | Returns the maximum value in a sequence of Double values. | |

Max | Returns the maximum value in a sequence of Int32 values. | |

Max | Returns the maximum value in a sequence of Int64 values. | |

Max | Returns the maximum value in a sequence of nullable Decimal values. | |

Max | Returns the maximum value in a sequence of nullable Double values. | |

Max | Returns the maximum value in a sequence of nullable Int32 values. | |

Max | Returns the maximum value in a sequence of nullable Int64 values. | |

Max | Returns the maximum value in a sequence of nullable Single values. | |

Max | Returns the maximum value in a sequence of Single values. | |

Max | Returns the maximum value in a generic sequence. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum Decimal value. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum Double value. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum Int32 value. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum Int64 value. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum nullable Double value. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum nullable Single value. | |

Max | Invokes a transform function on each element of a sequence and returns the maximum Single value. | |

Max | Invokes a transform function on each element of a generic sequence and returns the maximum resulting value. | |

Min | Returns the minimum value in a sequence of Decimal values. | |

Min | Returns the minimum value in a sequence of Double values. | |

Min | Returns the minimum value in a sequence of Int32 values. | |

Min | Returns the minimum value in a sequence of Int64 values. | |

Min | Returns the minimum value in a sequence of nullable Decimal values. | |

Min | Returns the minimum value in a sequence of nullable Double values. | |

Min | Returns the minimum value in a sequence of nullable Int32 values. | |

Min | Returns the minimum value in a sequence of nullable Int64 values. | |

Min | Returns the minimum value in a sequence of nullable Single values. | |

Min | Returns the minimum value in a sequence of Single values. | |

Min | Returns the minimum value in a generic sequence. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum Decimal value. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum Double value. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum Int32 value. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum Int64 value. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum nullable Double value. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum nullable Single value. | |

Min | Invokes a transform function on each element of a sequence and returns the minimum Single value. | |

Min | Invokes a transform function on each element of a generic sequence and returns the minimum resulting value. | |

OfType | Filters the elements of an IEnumerable based on a specified type. | |

OrderBy | Sorts the elements of a sequence in ascending order according to a key. | |

OrderBy | Sorts the elements of a sequence in ascending order by using a specified comparer. | |

OrderByDescending | Sorts the elements of a sequence in descending order according to a key. | |

OrderByDescending | Sorts the elements of a sequence in descending order by using a specified comparer. | |

Prepend | Adds a value to the beginning of the sequence. | |

Range | Generates a sequence of integral numbers within a specified range. | |

Repeat | Generates a sequence that contains one repeated value. | |

Reverse | Inverts the order of the elements in a sequence. | |

Select | Projects each element of a sequence into a new form. | |

Select | Projects each element of a sequence into a new form by incorporating the element's index. | |

SelectMany | Projects each element of a sequence to an IEnumerable and flattens the resulting sequences into one sequence. | |

SelectMany | Projects each element of a sequence to an IEnumerable, and flattens the resulting sequences into one sequence. The index of each source element is used in the projected form of that element. | |

SelectMany | Projects each element of a sequence to an IEnumerable, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. | |

SelectMany | Projects each element of a sequence to an IEnumerable, 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. | |

SequenceEqual | Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type. | |

SequenceEqual | Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer. | |

Single | Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence. | |

Single | Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists. | |

SingleOrDefault | 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. | |

SingleOrDefault | 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. | |

Skip | Bypasses a specified number of elements in a sequence and then returns the remaining elements. | |

SkipWhile | Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. | |

SkipWhile | 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. | |

Sum | Computes the sum of a sequence of Decimal values. | |

Sum | Computes the sum of a sequence of Double values. | |

Sum | Computes the sum of a sequence of Int32 values. | |

Sum | Computes the sum of a sequence of Int64 values. | |

Sum | Computes the sum of a sequence of nullable Decimal values. | |

Sum | Computes the sum of a sequence of nullable Double values. | |

Sum | Computes the sum of a sequence of nullable Int32 values. | |

Sum | Computes the sum of a sequence of nullable Int64 values. | |

Sum | Computes the sum of a sequence of nullable Single values. | |

Sum | Computes the sum of a sequence of Single values. | |

Sum | Computes the sum of the sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence. | |

Sum | Computes the sum of the sequence of Double values that are obtained by invoking a transform function on each element of the input sequence. | |

Sum | Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence. | |

Sum | Computes the sum of the sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence. | |

Sum | 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. | |

Sum | 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. | |

Sum | 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. | |

Sum | 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. | |

Sum | 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. | |

Sum | Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence. | |

Take | Returns a specified number of contiguous elements from the start of a sequence. | |

TakeWhile | Returns elements from a sequence as long as a specified condition is true. | |

TakeWhile | 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. | |

ThenBy | Performs a subsequent ordering of the elements in a sequence in ascending order according to a key. | |

ThenBy | Performs a subsequent ordering of the elements in a sequence in ascending order by using a specified comparer. | |

ThenByDescending | Performs a subsequent ordering of the elements in a sequence in descending order, according to a key. | |

ThenByDescending | Performs a subsequent ordering of the elements in a sequence in descending order by using a specified comparer. | |

ToArray | Creates an array from a IEnumerable. | |

ToDictionary | Creates a Dictionary from an IEnumerable according to a specified key selector function. | |

ToDictionary | Creates a Dictionary from an IEnumerable according to a specified key selector function and key comparer. | |

ToDictionary | Creates a Dictionary from an IEnumerable according to specified key selector and element selector functions. | |

ToDictionary | Creates a Dictionary from an IEnumerable according to a specified key selector function, a comparer, and an element selector function. | |

ToHashSet | Creates a HashSet from an IEnumerable. | |

ToHashSet | Creates a
HashSet from an
IEnumerable using the | |

ToList | Creates a List from an IEnumerable. | |

ToLookup | Creates a Lookup from an IEnumerable according to a specified key selector function. | |

ToLookup | Creates a Lookup from an IEnumerable according to a specified key selector function and key comparer. | |

ToLookup | Creates a Lookup from an IEnumerable according to specified key selector and element selector functions. | |

ToLookup | Creates a Lookup from an IEnumerable according to a specified key selector function, a comparer and an element selector function. | |

Union | Produces the set union of two sequences by using the default equality comparer. | |

Union | Produces the set union of two sequences by using a specified IEqualityComparer. | |

Where | Filters a sequence of values based on a predicate. | |

Where | Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function. | |

Zip | Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results. |

The methods in this class provide an implementation of the standard query operators for querying data sources that implement IEnumerable. The standard query operators are general purpose methods that follow the LINQ pattern and enable you to express traversal, filter, and projection operations over data in any .NET-based programming language.

The majority of the methods in this class are defined as extension methods that extend IEnumerable. This means they can be called like an instance method on any object that implements IEnumerable.

Methods that are used in a query that returns a sequence of values do not consume the target data until the query object is enumerated. This is known as deferred execution. Methods that are used in a query that returns a singleton value execute and consume the target data immediately.

**Universal Windows Platform**

Available since 8

**.NET Framework**

Available since 3.5

**Portable Class Library**

Supported in: portable .NET platforms

**Silverlight**

Available since 2.0

**Windows Phone Silverlight**

Available since 7.0

**Windows Phone**

Available since 8.1

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