IDictionary.Item Property

PropertyCollection.IDictionary.Item Property (Object)

 

Gets or sets the element with the specified key.

Namespace:   System.DirectoryServices
Assembly:  System.DirectoryServices (in System.DirectoryServices.dll)

object IDictionary.this[
	object key
] { get; set; }

Parameters

key
Type: System.Object

The key of the element to get or set.

Property Value

Type: System.Object

The element with the specified key.

Exception Condition
ArgumentNullException

key is null.

NotSupportedException

The property is set and the IDictionary object is read-only.

-or-

The property is set, key does not exist in the collection, and the IDictionary has a fixed size.

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 Item 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 Item property overwrites the old value. In contrast, the Add method does not modify existing elements.

The following example shows how to implement the Item property. This code example is part of a larger example provided for the IDictionary class.

public object this[object key]
{
    get
    {   
        // If this key is in the dictionary, return its value.
        Int32 index;
        if (TryGetIndexOfKey(key, out index))
        {
            // The key was found; return its value.
            return items[index].Value;
        } 
        else
        {
            // The key was not found; return null.
            return null;
        }
    }

    set
    {
        // If this key is in the dictionary, change its value. 
        Int32 index;
        if (TryGetIndexOfKey(key, out index))
        {
            // 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);
        }
    }
}

.NET Framework
Available since 2.0
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