Add Method

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

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

public void Add(
	Object key,
	Object value
)

Parameters

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

Implements

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.

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