Add Method

[This documentation is for preview only, and is subject to change in later releases. Blank topics are included as placeholders.]

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

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

virtual void Add(
	Object^ key, 
	Object^ value
) sealed


Type: System..::..Object
The key of the element to add.
Type: System..::..Object
The value of the element to add. The value can be nullNothingnullptrunita null reference (Nothing in Visual Basic).


IDictionary..::..Add(Object, Object)

A key cannot be nullNothingnullptrunita null reference (Nothing in Visual Basic), 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.