Hashtable.Add Method (Object, Object)


Adds an element with the specified key and value into the Hashtable.

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

abstract Add : 
        key:Object *
        value:Object -> unit
override Add : 
        key:Object *
        value:Object -> unit


Type: System.Object

The key of the element to add.

Type: System.Object

The value of the element to add. The value can be null.

Exception Condition

key is null.


An element with the same key already exists in the Hashtable.


The Hashtable is read-only.


The Hashtable has a fixed size.

A key cannot be null, but a value can be.

An object that has no correlation between its state and its hash code value should typically not be used as the key. For example, String objects are better than StringBuilder objects for use as keys.

You can also use the Item property to add new elements by setting the value of a key that does not exist in the Hashtable; for example, myCollection["myNonexistentKey"] = myValue. However, if the specified key already exists in the Hashtable, setting the Item property overwrites the old value. In contrast, the Add method does not modify existing elements.

If Count is less than the capacity of the Hashtable, this method is an O(1) operation. If the capacity needs to be increased to accommodate the new element, this method becomes an O(n) operation, where n is Count.

The following example shows how to add elements to the Hashtable.

No code example is currently available or this language may not be supported.

Universal Windows Platform
Available since 10
.NET Framework
Available since 1.1
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