IEnumerable(T) Interface
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IEnumerable<T> Interface

 

Exposes the enumerator, which supports a simple iteration over a collection of a specified type.

To browse the .NET Framework source code for this type, see the Reference Source.

Namespace:   System.Collections.Generic
Assembly:  mscorlib (in mscorlib.dll)

public interface IEnumerable<out T> : IEnumerable

Type Parameters

outT

The type of objects to enumerate.

NameDescription
System_CAPS_pubmethodGetEnumerator()

Returns an enumerator that iterates through the collection.

NameDescription
System_CAPS_pubmethodAggregate<TSource>(Func<TSource, TSource, TSource>)

Overloaded. Applies an accumulator function over a sequence.(Defined by Enumerable.)

System_CAPS_pubmethodAggregate<TSource, TAccumulate>(TAccumulate, Func<TAccumulate, TSource, TAccumulate>)

Overloaded. Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.(Defined by Enumerable.)

System_CAPS_pubmethodAggregate<TSource, TAccumulate, TResult>(TAccumulate, Func<TAccumulate, TSource, TAccumulate>, Func<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.)

System_CAPS_pubmethodAll<TSource>(Func<TSource, Boolean>)

Determines whether all elements of a sequence satisfy a condition.(Defined by Enumerable.)

System_CAPS_pubmethodAncestors<T>()

Overloaded. Returns a collection of elements that contains the ancestors of every node in the source collection.(Defined by Extensions.)

System_CAPS_pubmethodAncestors<T>(XName)

Overloaded. Returns a filtered collection of elements that contains the ancestors of every node in the source collection. Only elements that have a matching XName are included in the collection.(Defined by Extensions.)

System_CAPS_pubmethodAny<TSource>()

Overloaded. Determines whether a sequence contains any elements.(Defined by Enumerable.)

System_CAPS_pubmethodAny<TSource>(Func<TSource, Boolean>)

Overloaded. Determines whether any element of a sequence satisfies a condition.(Defined by Enumerable.)

System_CAPS_pubmethodAsEnumerable<TSource>()

Returns the input typed as IEnumerable<T>.(Defined by Enumerable.)

System_CAPS_pubmethodAsParallel<TSource>()

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

System_CAPS_pubmethodAsQueryable<TElement>()

Overloaded. Converts a generic IEnumerable<T> to a generic IQueryable<T>.(Defined by Queryable.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodAverage<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodCast<TResult>()

Casts the elements of an IEnumerable to the specified type.(Defined by Enumerable.)

System_CAPS_pubmethodConcat<TSource>(IEnumerable<TSource>)

Concatenates two sequences.(Defined by Enumerable.)

System_CAPS_pubmethodContains<TSource>(TSource)

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

System_CAPS_pubmethodContains<TSource>(TSource, IEqualityComparer<TSource>)

Overloaded. Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.(Defined by Enumerable.)

System_CAPS_pubmethodCopyToDataTable<T>()

Overloaded. Returns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object where the generic parameter T is DataRow. (Defined by DataTableExtensions.)

System_CAPS_pubmethodCopyToDataTable<T>(DataTable, LoadOption)

Overloaded. Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.(Defined by DataTableExtensions.)

System_CAPS_pubmethodCopyToDataTable<T>(DataTable, LoadOption, FillErrorEventHandler)

Overloaded. Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter T is DataRow.(Defined by DataTableExtensions.)

System_CAPS_pubmethodCount<TSource>()

Overloaded. Returns the number of elements in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethodCount<TSource>(Func<TSource, Boolean>)

Overloaded. Returns a number that represents how many elements in the specified sequence satisfy a condition.(Defined by Enumerable.)

System_CAPS_pubmethodDefaultIfEmpty<TSource>()

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.)

System_CAPS_pubmethodDefaultIfEmpty<TSource>(TSource)

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

System_CAPS_pubmethodDescendantNodes<T>()

Returns a collection of the descendant nodes of every document and element in the source collection.(Defined by Extensions.)

System_CAPS_pubmethodDescendants<T>()

Overloaded. Returns a collection of elements that contains the descendant elements of every element and document in the source collection.(Defined by Extensions.)

System_CAPS_pubmethodDescendants<T>(XName)

Overloaded. Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.(Defined by Extensions.)

System_CAPS_pubmethodDistinct<TSource>()

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

System_CAPS_pubmethodDistinct<TSource>(IEqualityComparer<TSource>)

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

System_CAPS_pubmethodElementAt<TSource>(Int32)

Returns the element at a specified index in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethodElementAtOrDefault<TSource>(Int32)

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

System_CAPS_pubmethodElements<T>()

Overloaded. Returns a collection of the child elements of every element and document in the source collection.(Defined by Extensions.)

System_CAPS_pubmethodElements<T>(XName)

Overloaded. Returns a filtered collection of the child elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.(Defined by Extensions.)

System_CAPS_pubmethodExcept<TSource>(IEnumerable<TSource>)

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

System_CAPS_pubmethodExcept<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)

Overloaded. Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values.(Defined by Enumerable.)

System_CAPS_pubmethodFirst<TSource>()

Overloaded. Returns the first element of a sequence.(Defined by Enumerable.)

System_CAPS_pubmethodFirst<TSource>(Func<TSource, Boolean>)

Overloaded. Returns the first element in a sequence that satisfies a specified condition.(Defined by Enumerable.)

System_CAPS_pubmethodFirstOrDefault<TSource>()

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

System_CAPS_pubmethodFirstOrDefault<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodGroupBy<TSource, TKey>(Func<TSource, TKey>)

Overloaded. Groups the elements of a sequence according to a specified key selector function.(Defined by Enumerable.)

System_CAPS_pubmethodGroupBy<TSource, TKey>(Func<TSource, TKey>, IEqualityComparer<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.)

System_CAPS_pubmethodGroupBy<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, 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.)

System_CAPS_pubmethodGroupBy<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<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.)

System_CAPS_pubmethodGroupBy<TSource, TKey, TResult>(Func<TSource, TKey>, Func<TKey, IEnumerable<TSource>, 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.)

System_CAPS_pubmethodGroupBy<TSource, TKey, TResult>(Func<TSource, TKey>, Func<TKey, IEnumerable<TSource>, TResult>, IEqualityComparer<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.)

System_CAPS_pubmethodGroupBy<TSource, TKey, TElement, TResult>(Func<TSource, TKey>, Func<TSource, TElement>, Func<TKey, IEnumerable<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.)

System_CAPS_pubmethodGroupBy<TSource, TKey, TElement, TResult>(Func<TSource, TKey>, Func<TSource, TElement>, Func<TKey, IEnumerable<TElement>, TResult>, IEqualityComparer<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.)

System_CAPS_pubmethodGroupJoin<TOuter, TInner, TKey, TResult>(IEnumerable<TInner>, Func<TOuter, TKey>, Func<TInner, TKey>, Func<TOuter, IEnumerable<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.)

System_CAPS_pubmethodGroupJoin<TOuter, TInner, TKey, TResult>(IEnumerable<TInner>, Func<TOuter, TKey>, Func<TInner, TKey>, Func<TOuter, IEnumerable<TInner>, TResult>, IEqualityComparer<TKey>)

Overloaded. Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer<T> is used to compare keys.(Defined by Enumerable.)

System_CAPS_pubmethodInDocumentOrder<T>()

Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.(Defined by Extensions.)

System_CAPS_pubmethodIntersect<TSource>(IEnumerable<TSource>)

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

System_CAPS_pubmethodIntersect<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)

Overloaded. Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values.(Defined by Enumerable.)

System_CAPS_pubmethodJoin<TOuter, TInner, TKey, TResult>(IEnumerable<TInner>, Func<TOuter, TKey>, Func<TInner, TKey>, Func<TOuter, 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.)

System_CAPS_pubmethodJoin<TOuter, TInner, TKey, TResult>(IEnumerable<TInner>, Func<TOuter, TKey>, Func<TInner, TKey>, Func<TOuter, TInner, TResult>, IEqualityComparer<TKey>)

Overloaded. Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer<T> is used to compare keys.(Defined by Enumerable.)

System_CAPS_pubmethodLast<TSource>()

Overloaded. Returns the last element of a sequence.(Defined by Enumerable.)

System_CAPS_pubmethodLast<TSource>(Func<TSource, Boolean>)

Overloaded. Returns the last element of a sequence that satisfies a specified condition.(Defined by Enumerable.)

System_CAPS_pubmethodLastOrDefault<TSource>()

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

System_CAPS_pubmethodLastOrDefault<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodLongCount<TSource>()

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

System_CAPS_pubmethodLongCount<TSource>(Func<TSource, Boolean>)

Overloaded. Returns an Int64 that represents how many elements in a sequence satisfy a condition.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>()

Overloaded. Returns the maximum value in a generic sequence.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Decimal>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Decimal value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Double>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Double value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Int32>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int32 value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Int64>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int64 value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Nullable<Decimal>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Nullable<Double>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Double value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Nullable<Int32>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Nullable<Int64>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Nullable<Single>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Single value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource>(Func<TSource, Single>)

Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Single value.(Defined by Enumerable.)

System_CAPS_pubmethodMax<TSource, TResult>(Func<TSource, TResult>)

Overloaded. Invokes a transform function on each element of a generic sequence and returns the maximum resulting value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>()

Overloaded. Returns the minimum value in a generic sequence.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Decimal>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Decimal value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Double>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Double value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Int32>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int32 value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Int64>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int64 value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Nullable<Decimal>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Nullable<Double>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Double value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Nullable<Int32>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Nullable<Int64>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Nullable<Single>>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Single value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource>(Func<TSource, Single>)

Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Single value.(Defined by Enumerable.)

System_CAPS_pubmethodMin<TSource, TResult>(Func<TSource, TResult>)

Overloaded. Invokes a transform function on each element of a generic sequence and returns the minimum resulting value.(Defined by Enumerable.)

System_CAPS_pubmethodNodes<T>()

Returns a collection of the child nodes of every document and element in the source collection.(Defined by Extensions.)

System_CAPS_pubmethodOfType<TResult>()

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

System_CAPS_pubmethodOrderBy<TSource, TKey>(Func<TSource, TKey>)

Overloaded. Sorts the elements of a sequence in ascending order according to a key.(Defined by Enumerable.)

System_CAPS_pubmethodOrderBy<TSource, TKey>(Func<TSource, TKey>, IComparer<TKey>)

Overloaded. Sorts the elements of a sequence in ascending order by using a specified comparer.(Defined by Enumerable.)

System_CAPS_pubmethodOrderByDescending<TSource, TKey>(Func<TSource, TKey>)

Overloaded. Sorts the elements of a sequence in descending order according to a key.(Defined by Enumerable.)

System_CAPS_pubmethodOrderByDescending<TSource, TKey>(Func<TSource, TKey>, IComparer<TKey>)

Overloaded. Sorts the elements of a sequence in descending order by using a specified comparer.(Defined by Enumerable.)

System_CAPS_pubmethodRemove<T>()

Overloaded. Removes every node in the source collection from its parent node.(Defined by Extensions.)

System_CAPS_pubmethodReverse<TSource>()

Inverts the order of the elements in a sequence.(Defined by Enumerable.)

System_CAPS_pubmethodSelect<TSource, TResult>(Func<TSource, TResult>)

Overloaded. Projects each element of a sequence into a new form.(Defined by Enumerable.)

System_CAPS_pubmethodSelect<TSource, TResult>(Func<TSource, Int32, TResult>)

Overloaded. Projects each element of a sequence into a new form by incorporating the element's index.(Defined by Enumerable.)

System_CAPS_pubmethodSelectMany<TSource, TResult>(Func<TSource, IEnumerable<TResult>>)

Overloaded. Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence.(Defined by Enumerable.)

System_CAPS_pubmethodSelectMany<TSource, TResult>(Func<TSource, Int32, IEnumerable<TResult>>)

Overloaded. Projects each element of a sequence to an IEnumerable<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.)

System_CAPS_pubmethodSelectMany<TSource, TCollection, TResult>(Func<TSource, IEnumerable<TCollection>>, Func<TSource, TCollection, TResult>)

Overloaded. Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.(Defined by Enumerable.)

System_CAPS_pubmethodSelectMany<TSource, TCollection, TResult>(Func<TSource, Int32, IEnumerable<TCollection>>, Func<TSource, TCollection, TResult>)

Overloaded. Projects each element of a sequence to an IEnumerable<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.)

System_CAPS_pubmethodSequenceEqual<TSource>(IEnumerable<TSource>)

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

System_CAPS_pubmethodSequenceEqual<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)

Overloaded. Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>.(Defined by Enumerable.)

System_CAPS_pubmethodSingle<TSource>()

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.)

System_CAPS_pubmethodSingle<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodSingleOrDefault<TSource>()

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.)

System_CAPS_pubmethodSingleOrDefault<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodSkip<TSource>(Int32)

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

System_CAPS_pubmethodSkipWhile<TSource>(Func<TSource, Boolean>)

Overloaded. Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.(Defined by Enumerable.)

System_CAPS_pubmethodSkipWhile<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, Nullable<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.)

System_CAPS_pubmethodSum<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodTake<TSource>(Int32)

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

System_CAPS_pubmethodTakeWhile<TSource>(Func<TSource, Boolean>)

Overloaded. Returns elements from a sequence as long as a specified condition is true.(Defined by Enumerable.)

System_CAPS_pubmethodTakeWhile<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodToArray<TSource>()

Creates an array from a IEnumerable<T>.(Defined by Enumerable.)

System_CAPS_pubmethodToDictionary<TSource, TKey>(Func<TSource, TKey>)

Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function.(Defined by Enumerable.)

System_CAPS_pubmethodToDictionary<TSource, TKey>(Func<TSource, TKey>, IEqualityComparer<TKey>)

Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function and key comparer.(Defined by Enumerable.)

System_CAPS_pubmethodToDictionary<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>)

Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to specified key selector and element selector functions.(Defined by Enumerable.)

System_CAPS_pubmethodToDictionary<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>)

Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function.(Defined by Enumerable.)

System_CAPS_pubmethodToList<TSource>()

Creates a List<T> from an IEnumerable<T>.(Defined by Enumerable.)

System_CAPS_pubmethodToLookup<TSource, TKey>(Func<TSource, TKey>)

Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function.(Defined by Enumerable.)

System_CAPS_pubmethodToLookup<TSource, TKey>(Func<TSource, TKey>, IEqualityComparer<TKey>)

Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function and key comparer.(Defined by Enumerable.)

System_CAPS_pubmethodToLookup<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>)

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

System_CAPS_pubmethodToLookup<TSource, TKey, TElement>(Func<TSource, TKey>, Func<TSource, TElement>, IEqualityComparer<TKey>)

Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function.(Defined by Enumerable.)

System_CAPS_pubmethodUnion<TSource>(IEnumerable<TSource>)

Overloaded. Produces the set union of two sequences by using the default equality comparer.(Defined by Enumerable.)

System_CAPS_pubmethodUnion<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)

Overloaded. Produces the set union of two sequences by using a specified IEqualityComparer<T>.(Defined by Enumerable.)

System_CAPS_pubmethodWhere<TSource>(Func<TSource, Boolean>)

Overloaded. Filters a sequence of values based on a predicate.(Defined by Enumerable.)

System_CAPS_pubmethodWhere<TSource>(Func<TSource, 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.)

System_CAPS_pubmethodZip<TFirst, TSecond, TResult>(IEnumerable<TSecond>, Func<TFirst, TSecond, TResult>)

Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results.(Defined by Enumerable.)

System_CAPS_noteNote

To view the .NET Framework source code for this type, see the Reference Source. You can browse through the source code online, download the reference for offline viewing, and step through the sources (including patches and updates) during debugging; see instructions.

IEnumerable<T> is the base interface for collections in the System.Collections.Generic namespace such as List<T>, Dictionary<TKey, TValue>, and Stack<T> and other generic collections such as ObservableCollection<T> and ConcurrentStack<T>. Collections that implement IEnumerable<T> can be enumerated by using the foreach statement. For the non-generic version of this interface, see System.Collections.IEnumerable.

For the non-generic version of this interface, see System.Collections.IEnumerable.

IEnumerable<T> contains a single method that you must implement when implementing this interface; GetEnumerator, which returns an IEnumerator<T> object. The returned IEnumerator<T> provides the ability to iterate through the collection by exposing a Current property.

Notes to Implementers:

IEnumerable<T> is included for parity with non-generic collections; implementing IEnumerable<T> allows a generic collection to be passed to a method that expects an IEnumerable object.

The following example demonstrates how to implement the IEnumerable<T> interface and how to use that implementation to create a LINQ query. When you implement IEnumerable<T>, you must also implement IEnumerator<T> or, for C# only, you can use the yield (C# Reference) keyword. Implementing IEnumerator<T> also requires IDisposable to be implemented, which you will see in this example.

using System;
using System.IO;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

public class App
{
    // Excercise the Iterator and show that it's more
    // performant.
    public static void Main()
    {
        TestStreamReaderEnumerable();
        Console.WriteLine("---");
        TestReadingFile();
    }

    public static void TestStreamReaderEnumerable()
	{
		// Check the memory before the iterator is used.
		long memoryBefore = GC.GetTotalMemory(true);
      IEnumerable<String> stringsFound;
		// Open a file with the StreamReaderEnumerable and check for a string.
      try {
         stringsFound =
               from line in new StreamReaderEnumerable(@"c:\temp\tempFile.txt")
               where line.Contains("string to search for")
               select line;
         Console.WriteLine("Found: " + stringsFound.Count());
      }
      catch (FileNotFoundException) {
         Console.WriteLine(@"This example requires a file named C:\temp\tempFile.txt.");
         return;
      }

		// Check the memory after the iterator and output it to the console.
		long memoryAfter = GC.GetTotalMemory(false);
		Console.WriteLine("Memory Used With Iterator = \t"
            + string.Format(((memoryAfter - memoryBefore) / 1000).ToString(), "n") + "kb");
	}

    public static void TestReadingFile()
	{
		long memoryBefore = GC.GetTotalMemory(true);
      StreamReader sr;
      try {
         sr = File.OpenText("c:\\temp\\tempFile.txt");
      }
      catch (FileNotFoundException) {
         Console.WriteLine(@"This example requires a file named C:\temp\tempFile.txt.");
         return;
      }

        // Add the file contents to a generic list of strings.
		List<string> fileContents = new List<string>();
		while (!sr.EndOfStream) {
			fileContents.Add(sr.ReadLine());
		}

		// Check for the string.
		var stringsFound = 
            from line in fileContents
            where line.Contains("string to search for")
            select line;

        sr.Close();
        Console.WriteLine("Found: " + stringsFound.Count());

		// Check the memory after when the iterator is not used, and output it to the console.
		long memoryAfter = GC.GetTotalMemory(false);
		Console.WriteLine("Memory Used Without Iterator = \t" + 
            string.Format(((memoryAfter - memoryBefore) / 1000).ToString(), "n") + "kb");
	}
}

// A custom class that implements IEnumerable(T). When you implement IEnumerable(T), 
// you must also implement IEnumerable and IEnumerator(T).
public class StreamReaderEnumerable : IEnumerable<string>
{
    private string _filePath;
    public StreamReaderEnumerable(string filePath)
    {
        _filePath = filePath;
    }

    // Must implement GetEnumerator, which returns a new StreamReaderEnumerator.
    public IEnumerator<string> GetEnumerator()
    {
        return new StreamReaderEnumerator(_filePath);
    }

    // Must also implement IEnumerable.GetEnumerator, but implement as a private method.
    private IEnumerator GetEnumerator1()
    {
        return this.GetEnumerator();
    }
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator1();
    }
}

// When you implement IEnumerable(T), you must also implement IEnumerator(T), 
// which will walk through the contents of the file one line at a time.
// Implementing IEnumerator(T) requires that you implement IEnumerator and IDisposable.
public class StreamReaderEnumerator : IEnumerator<string>
{
    private StreamReader _sr;
    public StreamReaderEnumerator(string filePath)
    {
        _sr = new StreamReader(filePath);
    }

    private string _current;
    // Implement the IEnumerator(T).Current publicly, but implement 
    // IEnumerator.Current, which is also required, privately.
    public string Current
    {

        get
        {
            if (_sr == null || _current == null)
            {
                throw new InvalidOperationException();
            }

            return _current;
        }
    }

    private object Current1
    {

        get { return this.Current; }
    }

    object IEnumerator.Current
    {
        get { return Current1; }
    }

    // Implement MoveNext and Reset, which are required by IEnumerator.
    public bool MoveNext()
    {
        _current = _sr.ReadLine();
        if (_current == null)
            return false;
        return true;
    }

    public void Reset()
    {
        _sr.DiscardBufferedData();
        _sr.BaseStream.Seek(0, SeekOrigin.Begin);
        _current = null;
    }

    // Implement IDisposable, which is also implemented by IEnumerator(T).
    private bool disposedValue = false;
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (!this.disposedValue)
        {
            if (disposing)
            {
                // Dispose of managed resources.
            }
            _current = null;
            if (_sr != null) {
               _sr.Close();
               _sr.Dispose();
            }
        }

        this.disposedValue = true;
    }

     ~StreamReaderEnumerator()
    {
        Dispose(false);
    }
}
// This example displays output similar to the following:
//       Found: 2
//       Memory Used With Iterator =     33kb
//       ---
//       Found: 2
//       Memory Used Without Iterator =  206kb

For another C# example that demonstrates how to implement the IEnumerable<T> interface, see the Generics Sample. This sample uses the yield keyword instead of implementing IEnumerator<T>.

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
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
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