Parameters

key

The key whose value is to be gotten or set.

Value

The value associated with the specified key. On a get attempt, if the specified key is not found, a KeyNotFoundException is thrown. On a set attempt, if the specified key is not found, a new element using the specified key is created.

Exceptions

Type	Reason
ArgumentNullException	key is null.
KeyNotFoundException	During a get attempt, key is not found in the dictionary.

Remarks

The default value for value types is zero while that for reference types is ..

You can also use the Dictionary<TKey, TValue>.Item(TKey) property to add new elements by setting the value of a key that does not exist in the dictionary. However, if the specified key already exists in the dictionary, setting the Dictionary<TKey, TValue>.Item(TKey) property overwrites the old value. In contrast, the Dictionary<TKey, TValue>.Add(TKey,TValue) method does not modify existing elements.

A key cannot be ., but a value can be, if the value type TValue is a reference type.

Retrieving the value of this property is an O(1) operation; setting the property is also an O(1) operation.

Requirements

Namespace: System.Collections.Generic
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 2.0.0.0
Since: .NET 2.0