DictionaryBase.OnSet Method (Object, Object, Object)

 
System_CAPS_noteNote

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Performs additional custom processes before setting a value in the DictionaryBase instance.

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

abstract OnSet : 
        key:Object *
        oldValue:Object *
        newValue:Object -> unit
override OnSet : 
        key:Object *
        oldValue:Object *
        newValue:Object -> unit

Parameters

key
Type: System.Object

The key of the element to locate.

oldValue
Type: System.Object

The old value of the element associated with key.

newValue
Type: System.Object

The new value of the element associated with key.

The default implementation of this method is intended to be overridden by a derived class to perform some action before the specified element is set.

The On* methods are invoked only on the instance returned by the Dictionary property, but not on the instance returned by the InnerHashtable property.

The default implementation of this method is an O(1) operation.

Notes to Implementers:

This method allows implementers to define processes that must be performed before setting the specified element in the underlying System.Collections.Hashtable. By defining this method, implementers can add functionality to inherited methods without having to override all other methods.

OnSet is invoked before the standard Set behavior, whereas OnSetComplete is invoked after the standard Set behavior.

For example, implementers can restrict which values can be overwritten by performing a check inside OnSet.

The following code example implements the DictionaryBase class and uses that implementation to create a dictionary of String keys and values that have a Length of 5 characters or less.

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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