Gets or sets the element with the specified key.
Assembly: mscorlib (in mscorlib.dll)
This property provides the ability to access a specific element in the collection by using the following syntax: myCollection[key].
You can also use the property to add new elements by setting the value of a key that does not exist in the dictionary (for example, myCollection["myNonexistentKey"] = myValue). However, if the specified key already exists in the dictionary, setting the property overwrites the old value. In contrast, the Add method does not modify existing elements.
Implementations can vary in whether they allow the key to be Nothing.
The C# language uses the thisthis (C# Reference) keyword to define the indexers instead of implementing the property. Visual Basic implements as a default property, which provides the same indexing functionality.
The following code example demonstrates how to implement the property. This code example is part of a larger example provided for the IDictionary class.
Public Property Item(ByVal key As Object) As Object Implements IDictionary.Item Get ' If this key is in the dictionary, return its value. Dim index As Integer If TryGetIndexOfKey(key, index) Then ' The key was found return its value. Return items(index).Value Else ' The key was not found return null. Return Nothing End If End Get Set(ByVal value As Object) ' If this key is in the dictionary, change its value. Dim index As Integer If TryGetIndexOfKey(key, index) Then ' The key was found change its value. items(index).Value = value Else ' This key is not in the dictionary add this key/value pair. Add(key, value) End If End Set End Property