Collection<T> Class

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Provides the base class for a generic collection.

Inheritance Hierarchy

System.Object
  System.Collections.ObjectModel.Collection<T>
    System.Collections.ObjectModel.KeyedCollection<TKey, TItem>
    System.Collections.ObjectModel.ObservableCollection<T>
    System.ComponentModel.SortDescriptionCollection
    System.ServiceModel.Channels.BindingElementCollection
    System.ServiceModel.Channels.ChannelParameterCollection
    System.ServiceModel.Description.FaultDescriptionCollection
    System.ServiceModel.Description.MessageDescriptionCollection
    System.ServiceModel.Description.OperationDescriptionCollection
    System.ServiceModel.Syndication.SyndicationElementExtensionCollection

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

Syntax

'Declaration
<DebuggerDisplayAttribute("Count = {Count}")> _
<DefaultMemberAttribute("Item")> _
<ComVisibleAttribute(False)> _
Public Class Collection(Of T) _
    Implements IList(Of T), ICollection(Of T),  _
    IList, ICollection, IEnumerable(Of T), IEnumerable

[DebuggerDisplayAttribute("Count = {Count}")]
[DefaultMemberAttribute("Item")]
[ComVisibleAttribute(false)]
public class Collection<T> : IList<T>, 
    ICollection<T>, IList, ICollection, IEnumerable<T>, IEnumerable

Type Parameters

• T
  The type of elements in the collection.

The Collection<T> type exposes the following members.

Constructors

	Name	Description
	Collection<T>()	Initializes a new instance of the Collection<T> class that is empty.
	Collection<T>(IList<T>)	Initializes a new instance of the Collection<T> class as a wrapper for the specified list.

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Properties

	Name	Description
	Count	Gets the number of elements actually contained in the Collection<T>.
	Item	Gets or sets the element at the specified index.
	Items	Gets a IList<T> wrapper around the Collection<T>.

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Methods

	Name	Description
	Add	Adds an object to the end of the Collection<T>.
	Clear	Removes all elements from the Collection<T>.
	ClearItems	Removes all elements from the Collection<T>.
	Contains	Determines whether an element is in the Collection<T>.
	CopyTo	Copies the entire Collection<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.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetEnumerator	Returns an enumerator that iterates through the Collection<T>.
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	IndexOf	Searches for the specified object and returns the zero-based index of the first occurrence within the entire Collection<T>.
	Insert	Inserts an element into the Collection<T> at the specified index.
	InsertItem	Inserts an element into the Collection<T> 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 Collection<T>.
	RemoveAt	Removes the element at the specified index of the Collection<T>.
	RemoveItem	Removes the element at the specified index of the Collection<T>.
	SetItem	Replaces the element at the specified index.
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Extension Methods

	Name	Description
	Aggregate<T>(Func<T, T, T>)	Overloaded. Applies an accumulator function over a sequence. (Defined by Enumerable.)
	Aggregate<T, TAccumulate>(TAccumulate, Func<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<T, TAccumulate, TResult>(TAccumulate, Func<TAccumulate, T, 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.)
	All<T>	Determines whether all elements of a sequence satisfy a condition. (Defined by Enumerable.)
	Any<T>()	Overloaded. Determines whether a sequence contains any elements. (Defined by Enumerable.)
	Any<T>(Func<T, Boolean>)	Overloaded. Determines whether any element of a sequence satisfies a condition. (Defined by Enumerable.)
	AsEnumerable<T>	Returns the input typed as IEnumerable<T>. (Defined by Enumerable.)
	AsQueryable()	Overloaded. Converts an IEnumerable to an IQueryable. (Defined by Queryable.)
	AsQueryable<T>()	Overloaded. Converts a generic IEnumerable<T> to a generic IQueryable<T>. (Defined by Queryable.)
	Average<T>(Func<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<T>(Func<T, 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.)
	Average<T>(Func<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<T>(Func<T, 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.)
	Average<T>(Func<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<T>(Func<T, 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.)
	Average<T>(Func<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<T>(Func<T, 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.)
	Average<T>(Func<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<T>(Func<T, 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.)
	Cast<TResult>	Converts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
	Concat<T>	Concatenates two sequences. (Defined by Enumerable.)
	Contains<T>(T)	Overloaded. Determines whether a sequence contains a specified element by using the default equality comparer. (Defined by Enumerable.)
	Contains<T>(T, IEqualityComparer<T>)	Overloaded. Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
	Count<T>()	Overloaded. Returns the number of elements in a sequence. (Defined by Enumerable.)
	Count<T>(Func<T, Boolean>)	Overloaded. Returns a number that represents how many elements in the specified sequence satisfy a condition. (Defined by Enumerable.)
	DefaultIfEmpty<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<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<T>()	Overloaded. Returns distinct elements from a sequence by using the default equality comparer to compare values. (Defined by Enumerable.)
	Distinct<T>(IEqualityComparer<T>)	Overloaded. Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
	ElementAt<T>	Returns the element at a specified index in a sequence. (Defined by Enumerable.)
	ElementAtOrDefault<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<T>(IEnumerable<T>)	Overloaded. Produces the set difference of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.)
	Except<T>(IEnumerable<T>, IEqualityComparer<T>)	Overloaded. Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
	First<T>()	Overloaded. Returns the first element of a sequence. (Defined by Enumerable.)
	First<T>(Func<T, Boolean>)	Overloaded. Returns the first element in a sequence that satisfies a specified condition. (Defined by Enumerable.)
	FirstOrDefault<T>()	Overloaded. Returns the first element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.)
	FirstOrDefault<T>(Func<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<T, TKey>(Func<T, TKey>)	Overloaded. Groups the elements of a sequence according to a specified key selector function. (Defined by Enumerable.)
	GroupBy<T, TKey>(Func<T, 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.)
	GroupBy<T, TKey, TElement>(Func<T, TKey>, Func<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<T, TKey, TResult>(Func<T, TKey>, Func<TKey, IEnumerable<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<T, TKey, TElement>(Func<T, TKey>, Func<T, 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.)
	GroupBy<T, TKey, TResult>(Func<T, TKey>, Func<TKey, IEnumerable<T>, 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.)
	GroupBy<T, TKey, TElement, TResult>(Func<T, TKey>, Func<T, 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.)
	GroupBy<T, TKey, TElement, TResult>(Func<T, TKey>, Func<T, 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.)
	GroupJoin<T, TInner, TKey, TResult>(IEnumerable<TInner>, Func<T, TKey>, Func<TInner, TKey>, Func<T, 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.)
	GroupJoin<T, TInner, TKey, TResult>(IEnumerable<TInner>, Func<T, TKey>, Func<TInner, TKey>, Func<T, 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.)
	Intersect<T>(IEnumerable<T>)	Overloaded. Produces the set intersection of two sequences by using the default equality comparer to compare values. (Defined by Enumerable.)
	Intersect<T>(IEnumerable<T>, IEqualityComparer<T>)	Overloaded. Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values. (Defined by Enumerable.)
	Join<T, TInner, TKey, TResult>(IEnumerable<TInner>, Func<T, TKey>, Func<TInner, TKey>, Func<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<T, TInner, TKey, TResult>(IEnumerable<TInner>, Func<T, TKey>, Func<TInner, TKey>, Func<T, 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.)
	Last<T>()	Overloaded. Returns the last element of a sequence. (Defined by Enumerable.)
	Last<T>(Func<T, Boolean>)	Overloaded. Returns the last element of a sequence that satisfies a specified condition. (Defined by Enumerable.)
	LastOrDefault<T>()	Overloaded. Returns the last element of a sequence, or a default value if the sequence contains no elements. (Defined by Enumerable.)
	LastOrDefault<T>(Func<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<T>()	Overloaded. Returns an Int64 that represents the total number of elements in a sequence. (Defined by Enumerable.)
	LongCount<T>(Func<T, Boolean>)	Overloaded. Returns an Int64 that represents how many elements in a sequence satisfy a condition. (Defined by Enumerable.)
	Max<T>()	Overloaded. Returns the maximum value in a generic sequence. (Defined by Enumerable.)
	Max<T>(Func<T, Decimal>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Decimal value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Decimal>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value. (Defined by Enumerable.)
	Max<T>(Func<T, Double>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Double value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Double>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Double value. (Defined by Enumerable.)
	Max<T>(Func<T, Int32>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int32 value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Int32>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value. (Defined by Enumerable.)
	Max<T>(Func<T, Int64>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Int64 value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Int64>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value. (Defined by Enumerable.)
	Max<T>(Func<T, Single>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum Single value. (Defined by Enumerable.)
	Max<T>(Func<T, Nullable<Single>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the maximum nullable Single value. (Defined by Enumerable.)
	Max<T, TResult>(Func<T, TResult>)	Overloaded. Invokes a transform function on each element of a generic sequence and returns the maximum resulting value. (Defined by Enumerable.)
	Min<T>()	Overloaded. Returns the minimum value in a generic sequence. (Defined by Enumerable.)
	Min<T>(Func<T, Decimal>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Decimal value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Decimal>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value. (Defined by Enumerable.)
	Min<T>(Func<T, Double>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Double value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Double>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Double value. (Defined by Enumerable.)
	Min<T>(Func<T, Int32>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int32 value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Int32>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value. (Defined by Enumerable.)
	Min<T>(Func<T, Int64>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Int64 value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Int64>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value. (Defined by Enumerable.)
	Min<T>(Func<T, Single>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum Single value. (Defined by Enumerable.)
	Min<T>(Func<T, Nullable<Single>>)	Overloaded. Invokes a transform function on each element of a sequence and returns the minimum nullable Single value. (Defined by Enumerable.)
	Min<T, TResult>(Func<T, TResult>)	Overloaded. Invokes a transform function on each element of a generic sequence and returns the minimum resulting value. (Defined by Enumerable.)
	OfType<TResult>	Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
	OrderBy<T, TKey>(Func<T, TKey>)	Overloaded. Sorts the elements of a sequence in ascending order according to a key. (Defined by Enumerable.)
	OrderBy<T, TKey>(Func<T, TKey>, IComparer<TKey>)	Overloaded. Sorts the elements of a sequence in ascending order by using a specified comparer. (Defined by Enumerable.)
	OrderByDescending<T, TKey>(Func<T, TKey>)	Overloaded. Sorts the elements of a sequence in descending order according to a key. (Defined by Enumerable.)
	OrderByDescending<T, TKey>(Func<T, TKey>, IComparer<TKey>)	Overloaded. Sorts the elements of a sequence in descending order by using a specified comparer. (Defined by Enumerable.)
	Reverse<T>	Inverts the order of the elements in a sequence. (Defined by Enumerable.)
	Select<T, TResult>(Func<T, TResult>)	Overloaded. Projects each element of a sequence into a new form. (Defined by Enumerable.)
	Select<T, TResult>(Func<T, Int32, TResult>)	Overloaded. Projects each element of a sequence into a new form by incorporating the element's index. (Defined by Enumerable.)
	SelectMany<T, TResult>(Func<T, IEnumerable<TResult>>)	Overloaded. Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence. (Defined by Enumerable.)
	SelectMany<T, TResult>(Func<T, 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.)
	SelectMany<T, TCollection, TResult>(Func<T, Int32, IEnumerable<TCollection>>, Func<T, 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.)
	SelectMany<T, TCollection, TResult>(Func<T, IEnumerable<TCollection>>, Func<T, 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.)
	SequenceEqual<T>(IEnumerable<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<T>(IEnumerable<T>, IEqualityComparer<T>)	Overloaded. Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
	Single<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<T>(Func<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<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<T>(Func<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<T>	Bypasses a specified number of elements in a sequence and then returns the remaining elements. (Defined by Enumerable.)
	SkipWhile<T>(Func<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<T>(Func<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<T>(Func<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<T>(Func<T, 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.)
	Sum<T>(Func<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<T>(Func<T, 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.)
	Sum<T>(Func<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<T>(Func<T, 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.)
	Sum<T>(Func<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<T>(Func<T, 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.)
	Sum<T>(Func<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<T>(Func<T, 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.)
	Take<T>	Returns a specified number of contiguous elements from the start of a sequence. (Defined by Enumerable.)
	TakeWhile<T>(Func<T, Boolean>)	Overloaded. Returns elements from a sequence as long as a specified condition is true. (Defined by Enumerable.)
	TakeWhile<T>(Func<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<T>	Creates an array from a IEnumerable<T>. (Defined by Enumerable.)
	ToDictionary<T, TKey>(Func<T, TKey>)	Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to a specified key selector function. (Defined by Enumerable.)
	ToDictionary<T, TKey>(Func<T, 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.)
	ToDictionary<T, TKey, TElement>(Func<T, TKey>, Func<T, TElement>)	Overloaded. Creates a Dictionary<TKey, TValue> from an IEnumerable<T> according to specified key selector and element selector functions. (Defined by Enumerable.)
	ToDictionary<T, TKey, TElement>(Func<T, TKey>, Func<T, 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.)
	ToList<T>	Creates a List<T> from an IEnumerable<T>. (Defined by Enumerable.)
	ToLookup<T, TKey>(Func<T, TKey>)	Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to a specified key selector function. (Defined by Enumerable.)
	ToLookup<T, TKey>(Func<T, 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.)
	ToLookup<T, TKey, TElement>(Func<T, TKey>, Func<T, TElement>)	Overloaded. Creates a Lookup<TKey, TElement> from an IEnumerable<T> according to specified key selector and element selector functions. (Defined by Enumerable.)
	ToLookup<T, TKey, TElement>(Func<T, TKey>, Func<T, 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.)
	Union<T>(IEnumerable<T>)	Overloaded. Produces the set union of two sequences by using the default equality comparer. (Defined by Enumerable.)
	Union<T>(IEnumerable<T>, IEqualityComparer<T>)	Overloaded. Produces the set union of two sequences by using a specified IEqualityComparer<T>. (Defined by Enumerable.)
	Where<T>(Func<T, Boolean>)	Overloaded. Filters a sequence of values based on a predicate. (Defined by Enumerable.)
	Where<T>(Func<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<T, TSecond, TResult>	Merges two sequences by using the specified predicate function. (Defined by Enumerable.)

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Explicit Interface Implementations

	Name	Description
	ICollection.CopyTo	Copies the elements of the ICollection to an Array, starting at a particular Array index.
	ICollection<T>.IsReadOnly	Gets a value indicating whether the ICollection<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.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 into 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.

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Remarks

The Collection<T> class can be used immediately by creating an instance of one of its constructed types; all you have to do is specify the type of object to be contained in the collection. In addition, you can derive your own collection type from any constructed type, or derive a generic collection type from the Collection<T> class itself.

The Collection<T> class provides protected methods that can be used to customize its behavior when adding and removing items, clearing the collection, or setting the value of an existing item.

Most Collection<T> objects can be modified. However, a Collection<T> object that is initialized with a read-only IList<T> object cannot be modified. See ReadOnlyCollection<T> for a read-only version of this class.

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

Collection<T> accepts nulla null reference (Nothing in Visual Basic) as a valid value for reference types and allows duplicate elements.

Notes to Implementers

This base class is provided to make it easier for implementers to create a custom collection. Implementers are encouraged to extend this base class instead of creating their own.

Examples

This section contains two code examples. The first example demonstrates several properties and methods of the Collection<T> class. The second example shows how to derive a collection class from a constructed type of Collection<T>, and how to override the protected methods of Collection<T> to provide custom behavior.

Example 1

The following code example demonstrates many of the properties and methods of Collection<T>. The code example creates a collection of strings, uses the Add method to add several strings, displays the Count, and lists the strings. The example uses the IndexOf method to find the index of a string and the Contains method to determine whether a string is in the collection. The example inserts a string using the Insert method and retrieves and sets strings using the default Item property (the indexer in C#). The example removes strings by string identity using the Remove method and by index using the RemoveAt method. Finally, the Clear method is used to clear all strings from the collection.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.

Imports System.Collections.Generic
Imports System.Collections.ObjectModel

Public Class Example

    Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

        Dim dinosaurs As New Collection(Of String)

        dinosaurs.Add("Psitticosaurus")
        dinosaurs.Add("Caudipteryx")
        dinosaurs.Add("Compsognathus")
        dinosaurs.Add("Muttaburrasaurus")

        outputBlock.Text += String.Format("{0} dinosaurs:", dinosaurs.Count) & vbCrLf
        Display(outputBlock, dinosaurs)

        outputBlock.Text &= vbLf & String.Format("IndexOf(""Muttaburrasaurus"") {0}", _
          dinosaurs.IndexOf("Muttaburrasaurus")) & vbCrLf

        outputBlock.Text &= vbLf & String.Format("Contains(""Caudipteryx"") {0}", _
          dinosaurs.Contains("Caudipteryx")) & vbCrLf

        outputBlock.Text += String.Format(vbLf & "Insert(2, ""Nanotyrannus"")") & vbCrLf
        dinosaurs.Insert(2, "Nanotyrannus")
        Display(outputBlock, dinosaurs)

        outputBlock.Text += String.Format(vbLf & "dinosaurs(2): {0}", dinosaurs(2)) & vbCrLf

        outputBlock.Text &= vbLf & "dinosaurs(2) = ""Microraptor""" & vbCrLf
        dinosaurs(2) = "Microraptor"
        Display(outputBlock, dinosaurs)

        outputBlock.Text &= vbLf & "Remove(""Microraptor"")" & vbCrLf
        dinosaurs.Remove("Microraptor")
        Display(outputBlock, dinosaurs)

        outputBlock.Text &= vbLf & "RemoveAt(0)" & vbCrLf
        dinosaurs.RemoveAt(0)
        Display(outputBlock, dinosaurs)

        outputBlock.Text &= vbLf & "dinosaurs.Clear()" & vbCrLf
        dinosaurs.Clear()
        outputBlock.Text += String.Format("Count: {0}", dinosaurs.Count) & vbCrLf

    End Sub

    Private Shared Sub Display(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal cs As Collection(Of String))
        outputBlock.Text &= vbCrLf
        For Each item As String In cs
            outputBlock.Text &= item & vbCrLf
        Next item
    End Sub
End Class

' This code example produces the following output:
'
'4 dinosaurs:
'
'Psitticosaurus
'Caudipteryx
'Compsognathus
'Muttaburrasaurus
'
'IndexOf("Muttaburrasaurus"): 3
'
'Contains("Caudipteryx"): True
'
'Insert(2, "Nanotyrannus")
'
'Psitticosaurus
'Caudipteryx
'Nanotyrannus
'Compsognathus
'Muttaburrasaurus
'
'dinosaurs(2): Nanotyrannus
'
'dinosaurs(2) = "Microraptor"
'
'Psitticosaurus
'Caudipteryx
'Microraptor
'Compsognathus
'Muttaburrasaurus
'
'Remove("Microraptor")
'
'Psitticosaurus
'Caudipteryx
'Compsognathus
'Muttaburrasaurus
'
'RemoveAt(0)
'
'Caudipteryx
'Compsognathus
'Muttaburrasaurus
'
'dinosaurs.Clear()
'Count: 0

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      Collection<string> dinosaurs = new Collection<string>();

      dinosaurs.Add("Psitticosaurus");
      dinosaurs.Add("Caudipteryx");
      dinosaurs.Add("Compsognathus");
      dinosaurs.Add("Muttaburrasaurus");

      outputBlock.Text += String.Format("{0} dinosaurs:", dinosaurs.Count) + "\n";
      Display(outputBlock, dinosaurs);

      outputBlock.Text += String.Format("\nIndexOf(\"Muttaburrasaurus\"): {0}",
          dinosaurs.IndexOf("Muttaburrasaurus")) + "\n";

      outputBlock.Text += String.Format("\nContains(\"Caudipteryx\"): {0}",
          dinosaurs.Contains("Caudipteryx")) + "\n";

      outputBlock.Text += String.Format("\nInsert(2, \"Nanotyrannus\")") + "\n";
      dinosaurs.Insert(2, "Nanotyrannus");
      Display(outputBlock, dinosaurs);

      outputBlock.Text += String.Format("\ndinosaurs[2]: {0}", dinosaurs[2]) + "\n";

      outputBlock.Text += "\ndinosaurs[2] = \"Microraptor\"" + "\n";
      dinosaurs[2] = "Microraptor";
      Display(outputBlock, dinosaurs);

      outputBlock.Text += "\nRemove(\"Microraptor\")" + "\n";
      dinosaurs.Remove("Microraptor");
      Display(outputBlock, dinosaurs);

      outputBlock.Text += "\nRemoveAt(0)" + "\n";
      dinosaurs.RemoveAt(0);
      Display(outputBlock, dinosaurs);

      outputBlock.Text += "\ndinosaurs.Clear()" + "\n";
      dinosaurs.Clear();
      outputBlock.Text += String.Format("Count: {0}", dinosaurs.Count) + "\n";
   }

   private static void Display(System.Windows.Controls.TextBlock outputBlock, Collection<string> cs)
   {
      outputBlock.Text += "\n";
      foreach (string item in cs)
      {
         outputBlock.Text += item + "\n";
      }
   }
}

/* This code example produces the following output:

4 dinosaurs:

Psitticosaurus
Caudipteryx
Compsognathus
Muttaburrasaurus

IndexOf("Muttaburrasaurus"): 3

Contains("Caudipteryx"): True

Insert(2, "Nanotyrannus")

Psitticosaurus
Caudipteryx
Nanotyrannus
Compsognathus
Muttaburrasaurus

dinosaurs[2]: Nanotyrannus

dinosaurs[2] = "Microraptor"

Psitticosaurus
Caudipteryx
Microraptor
Compsognathus
Muttaburrasaurus

Remove("Microraptor")

Psitticosaurus
Caudipteryx
Compsognathus
Muttaburrasaurus

RemoveAt(0)

Caudipteryx
Compsognathus
Muttaburrasaurus

dinosaurs.Clear()
Count: 0
 */

Example 2

The following code example shows how to derive a collection class from a constructed type of the Collection<T> generic class, and how to override the protected InsertItem, RemoveItem, ClearItems, and SetItem methods to provide custom behavior for the Add, Insert, Remove, and Clear methods, and for setting the Item property.

The custom behavior provided by this example is a Changed notification event that is raised at the end of each of the protected methods. The Dinosaurs class inherits Collection<string> (Collection(Of String) in Visual Basic) and defines the Changed event, which uses a DinosaursChangedEventArgs class for the event information, and an enumeration to identify the kind of change.

The code example calls several properties and methods of Collection<T> to demonstrate the custom event.

Note:
To run this example, see Building Examples That Use a Demo Method and a TextBlock Control.

Imports System.Collections.Generic
Imports System.Collections.ObjectModel
Imports System.Windows.Controls

Public Class Dinosaurs
    Inherits Collection(Of String)

    Public Event Changed As EventHandler(Of DinosaursChangedEventArgs)

    Protected Overrides Sub InsertItem( _
        ByVal index As Integer, ByVal newItem As String)

        MyBase.InsertItem(index, newItem)

        RaiseEvent Changed(Me, New DinosaursChangedEventArgs( _
            ChangeType.Added, newItem, Nothing))
    End Sub

    Protected Overrides Sub SetItem(ByVal index As Integer, _
        ByVal newItem As String)

        Dim replaced As String = Items(index)
        MyBase.SetItem(index, newItem)

        RaiseEvent Changed(Me, New DinosaursChangedEventArgs( _
            ChangeType.Replaced, replaced, newItem))
    End Sub

    Protected Overrides Sub RemoveItem(ByVal index As Integer)

        Dim removedItem As String = Items(index)
        MyBase.RemoveItem(index)

        RaiseEvent Changed(Me, New DinosaursChangedEventArgs( _
            ChangeType.Removed, removedItem, Nothing))
    End Sub

    Protected Overrides Sub ClearItems()
        MyBase.ClearItems()

        RaiseEvent Changed(Me, New DinosaursChangedEventArgs( _
            ChangeType.Cleared, Nothing, Nothing))
    End Sub

End Class

' Event argument for the Changed event.
'
Public Class DinosaursChangedEventArgs
    Inherits EventArgs

    Public ReadOnly ChangedItem As String
    Public ReadOnly ChangeType As ChangeType
    Public ReadOnly ReplacedWith As String

    Public Sub New(ByVal change As ChangeType, ByVal item As String, _
        ByVal replacement As String)

        ChangeType = change
        ChangedItem = item
        ReplacedWith = replacement
    End Sub
End Class

Public Enum ChangeType
    Added
    Removed
    Replaced
    Cleared
End Enum

Public Class Example

    Private Shared _TextBlock As TextBlock

    Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)

        Example._TextBlock = outputBlock

        Dim dinosaurs As New Dinosaurs

        AddHandler dinosaurs.Changed, AddressOf ChangedHandler

        dinosaurs.Add("Psitticosaurus")
        dinosaurs.Add("Caudipteryx")
        dinosaurs.Add("Compsognathus")
        dinosaurs.Add("Muttaburrasaurus")

        Display(outputBlock, dinosaurs)

        outputBlock.Text &= String.Format(vbLf & "IndexOf(""Muttaburrasaurus""): {0}" & vbCrLf, _
            dinosaurs.IndexOf("Muttaburrasaurus"))

        outputBlock.Text &= String.Format(vbLf & "Contains(""Caudipteryx""): {0}" & vbCrLf, _
            dinosaurs.Contains("Caudipteryx"))

        outputBlock.Text &= String.Format(vbLf & "Insert(2, ""Nanotyrannus"")") & vbCrLf
        dinosaurs.Insert(2, "Nanotyrannus")

        outputBlock.Text &= String.Format(vbLf & "dinosaurs(2): {0}" & vbCrLf, dinosaurs(2))

        outputBlock.Text &= vbLf & "dinosaurs(2) = ""Microraptor""" & vbCrLf
        dinosaurs(2) = "Microraptor"

        outputBlock.Text &= vbLf & "Remove(""Microraptor"")" & vbCrLf
        dinosaurs.Remove("Microraptor")

        outputBlock.Text &= vbLf & "RemoveAt(0)" & vbCrLf
        dinosaurs.RemoveAt(0)

        Display(outputBlock, dinosaurs)

    End Sub

    Private Shared Sub Display(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal cs As Collection(Of String))
        _TextBlock.Text &= vbCrLf
        For Each item As String In cs
            _TextBlock.Text &= item & vbCrLf
        Next item
    End Sub

    Private Shared Sub ChangedHandler(ByVal source As Object, _
        ByVal e As DinosaursChangedEventArgs)

        If e.ChangeType = ChangeType.Replaced Then
            _TextBlock.Text &= String.Format("{0} was replaced with {1}", _
                e.ChangedItem, e.ReplacedWith) & vbCrLf

        ElseIf e.ChangeType = ChangeType.Cleared Then
            _TextBlock.Text &= "The dinosaur list was cleared." & vbCrLf

        Else
            _TextBlock.Text &= String.Format("{0} was {1}.", _
                e.ChangedItem, e.ChangeType) & vbCrLf
        End If
    End Sub

End Class
' This code example produces the following output:
'
'Psitticosaurus was Added.
'Caudipteryx was Added.
'Compsognathus was Added.
'Muttaburrasaurus was Added.
'
'Psitticosaurus
'Caudipteryx
'Compsognathus
'Muttaburrasaurus
'
'IndexOf("Muttaburrasaurus"): 3
'
'Contains("Caudipteryx"): True
'
'Insert(2, "Nanotyrannus")
'Nanotyrannus was Added.
'
'dinosaurs(2): Nanotyrannus
'
'dinosaurs(2) = "Microraptor"
'Nanotyrannus was replaced with Microraptor
'
'Remove("Microraptor")
'Microraptor was Removed.
'
'RemoveAt(0)
'Psitticosaurus was Removed.
'
'Caudipteryx
'Compsognathus
'Muttaburrasaurus

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Windows.Controls;

public class Dinosaurs : Collection<string>
{
    public event EventHandler<DinosaursChangedEventArgs> Changed;


    protected override void InsertItem(int index, string newItem)
    {
        base.InsertItem(index, newItem);

        EventHandler<DinosaursChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new DinosaursChangedEventArgs(
                ChangeType.Added, newItem, null));
        }
    }

    protected override void SetItem(int index, string newItem)
    {
        string replaced = Items[index];
        base.SetItem(index, newItem);

        EventHandler<DinosaursChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new DinosaursChangedEventArgs(
                ChangeType.Replaced, replaced, newItem));
        }
    }

    protected override void RemoveItem(int index)
    {
        string removedItem = Items[index];
        base.RemoveItem(index);

        EventHandler<DinosaursChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new DinosaursChangedEventArgs(
                ChangeType.Removed, removedItem, null));
        }
    }

    protected override void ClearItems()
    {
        base.ClearItems();

        EventHandler<DinosaursChangedEventArgs> temp = Changed;
        if (temp != null)
        {
            temp(this, new DinosaursChangedEventArgs(
                ChangeType.Cleared, null, null));
        }
    }
}

// Event argument for the Changed event.
//
public class DinosaursChangedEventArgs : EventArgs
{
    public readonly string ChangedItem;
    public readonly ChangeType ChangeType;
    public readonly string ReplacedWith;

    public DinosaursChangedEventArgs(ChangeType change, string item,
        string replacement)
    {
        ChangeType = change;
        ChangedItem = item;
        ReplacedWith = replacement;
    }
}

public enum ChangeType
{
    Added,
    Removed,
    Replaced,
    Cleared
};

public class Example
{

    private static TextBlock _textblock;


    public static void Demo(TextBlock outputBlock)
    {

        Example._textblock = outputBlock;

        Dinosaurs dinosaurs = new Dinosaurs();

        dinosaurs.Changed += ChangedHandler;

        dinosaurs.Add("Psitticosaurus");
        dinosaurs.Add("Caudipteryx");
        dinosaurs.Add("Compsognathus");
        dinosaurs.Add("Muttaburrasaurus");

        Display(dinosaurs);

        outputBlock.Text += String.Format("\nIndexOf(\"Muttaburrasaurus\"): {0}\n",
            dinosaurs.IndexOf("Muttaburrasaurus"));

        outputBlock.Text += String.Format("\nContains(\"Caudipteryx\"): {0}\n",
            dinosaurs.Contains("Caudipteryx"));

        outputBlock.Text += String.Format("\nInsert(2, \"Nanotyrannus\")\n");
        dinosaurs.Insert(2, "Nanotyrannus");

        outputBlock.Text += String.Format("\ndinosaurs[2]: {0}\n", dinosaurs[2]);

        outputBlock.Text += "\ndinosaurs[2] = \"Microraptor\"" + "\n";
        dinosaurs[2] = "Microraptor";

        outputBlock.Text += "\nRemove(\"Microraptor\")\n";
        dinosaurs.Remove("Microraptor");

        outputBlock.Text += "\nRemoveAt(0)\n";
        dinosaurs.RemoveAt(0);

        Display(dinosaurs);
    }

    private static void Display(Collection<string> cs)
    {
        _textblock.Text += "\n";
        foreach (string item in cs)
        {
            _textblock.Text += item + "\n";
        }
    }

    private static void ChangedHandler(object source,
        DinosaursChangedEventArgs e)
    {

        if (e.ChangeType == ChangeType.Replaced)
        {
            _textblock.Text += String.Format("{0} was replaced with {1}\n", e.ChangedItem,
                e.ReplacedWith);
        }
        else if (e.ChangeType == ChangeType.Cleared)
        {
            _textblock.Text += "The dinosaur list was cleared." + "\n";
        }
        else
        {
            _textblock.Text += String.Format("{0} was {1}.\n", e.ChangedItem, e.ChangeType);
        }
    }
}


/* This code example produces the following output:

Psitticosaurus was Added.
Caudipteryx was Added.
Compsognathus was Added.
Muttaburrasaurus was Added.

Psitticosaurus
Caudipteryx
Compsognathus
Muttaburrasaurus

IndexOf("Muttaburrasaurus"): 3

Contains("Caudipteryx"): True

Insert(2, "Nanotyrannus")
Nanotyrannus was Added.

dinosaurs[2]: Nanotyrannus

dinosaurs[2] = "Microraptor"
Nanotyrannus was replaced with Microraptor

Remove("Microraptor")
Microraptor was Removed.

RemoveAt(0)
Psitticosaurus was Removed.

Caudipteryx
Compsognathus
Muttaburrasaurus
 */

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

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

A Collection<T> can support multiple readers concurrently, as long as the collection is not modified. Even so, enumerating through a collection is intrinsically not a thread-safe procedure. To guarantee thread safety during enumeration, you can 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.

See Also

Reference

System.Collections.ObjectModel Namespace

ICollection<T>