Contains Method

ReadOnlyCollection<T>.Contains Method (T)


Determines whether an element is in the ReadOnlyCollection<T>.

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

public bool Contains(
	T value


Type: T

The object to locate in the ReadOnlyCollection<T>. The value can be null for reference types.

Return Value

Type: System.Boolean

true if value is found in the ReadOnlyCollection<T>; otherwise, false.

This method determines equality using the default equality comparer EqualityComparer<T>.Default.

This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.

The following code example demonstrates several members of the ReadOnlyCollection<T> class. The code example creates a List<T> of strings and adds four dinosaur names to it. The code example then wraps the list in a ReadOnlyCollection<T>.

After demonstrating the Count, Contains, Item, and IList.IndexOf members, the code example shows that the ReadOnlyCollection<T> is just a wrapper for the original List<T> by adding a new item to the List<T> and displaying the contents of the ReadOnlyCollection<T>.

Finally, the code example creates an array larger than the collection and uses the CopyTo method to insert the elements of the collection into the middle of the array.

private void synchButton_Click(System.Object sender, System.EventArgs e)
    // If the first displayed item is not the current item.
    if (dataRepeater1.FirstDisplayedItemIndex != dataRepeater1.CurrentItemIndex)
    // Make it the current item.
        dataRepeater1.CurrentItemIndex = dataRepeater1.FirstDisplayedItemIndex;

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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