IDictionary.Contains Method

Determines whether the IDictionary object contains an element with the specified key.

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

bool Contains(
	Object key


Type: System.Object
The key to locate in the IDictionary object.

Return Value

Type: System.Boolean
true if the IDictionary contains an element with the key; otherwise, false.


key is null.

Implementations can vary in whether they allow the key to be null.

Starting with the .NET Framework 2.0, this method uses the collection’s objects’ Equals and CompareTo methods on item to determine whether item exists. In the earlier versions of the .NET Framework, this determination was made by using the Equals and CompareTo methods of the item parameter on the objects in the collection.

The following code example demonstrates how to implement the Contains method. This code example is part of a larger example provided for the IDictionary class.

public bool Contains(object key)
   Int32 index;
   return TryGetIndexOfKey(key, out index);


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

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