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about_Functions_Advanced

Updated: May 8, 2014

Applies To: Windows PowerShell 2.0, Windows PowerShell 3.0, Windows PowerShell 4.0

TOPIC
    about_Functions_Advanced

SHORT DESCRIPTION
    Introduces advanced functions that act similar to cmdlets.

LONG DESCRIPTION
    Advanced functions allow you to write functions that can perform operations 
    that are similar to the operations you can perform with cmdlets. Advanced 
    functions are helpful when you want to quickly write a function without 
    having to write a compiled cmdlet using a Microsoft .NET Framework 
    language. These functions are also helpful when you want to restrict the
    functionality of a compiled cmdlet or when you want to write a function 
    that is similar to a compiled cmdlet.
 

    There is a difference between authoring a compiled cmdlet and an advanced
    function. Compiled cmdlets are .NET Framework classes that must be written
    in a .NET Framework language such as C#. In contrast, advanced functions 
    are written in the Windows PowerShell script language in the same way that
    other functions or script blocks are written.


    Advanced functions use the CmdletBinding attribute to identify them as 
    functions that act similar to cmdlets. The CmdletBinding attribute is 
    similar to the Cmdlet attribute that is used in compiled cmdlet classes to
    identify the class as a cmdlet. For more information about this attribute,
    see about_Functions_CmdletBindingAttribute.


    The following example shows a function that accepts a name and then prints
    a greeting using the supplied name. Also notice that this function defines
    a name that includes a verb (Send) and noun (Greeting) pair similar to the
    verb-noun pair of a compiled cmdlet. However, functions are not required 
    to have a verb-noun name. 


        function Send-Greeting
        {
          [CmdletBinding()]
          Param(
              [Parameter(Mandatory=$true)]
              [string] $Name
          )
          Process
          {
            write-host ("Hello " + $Name + "!")
          }
        }


    The parameters of the function are declared by using the Parameter 
    attribute. This attribute can be used alone, or it can be combined with 
    the Alias attribute or with several other parameter validation attributes.
    For more information about how to declare parameters (including dynamic
    parameters that are added at runtime), see
    about_Functions_Advanced_Parameters. 
 

    The actual work of the previous function is performed in the Process 
    block, which is equivalent to the ProcessingRecord method that is used by 
    compiled cmdlets to process the data that is passed to the cmdlet. This 
    block, along with the Begin and End blocks, is described in the 
    about_Functions_Advanced_Methods topic.


    Advanced functions differ from compiled cmdlets in the following ways: 

        - Advanced function parameter binding does not throw an exception when 
          an array of strings is bound to a Boolean parameter.

        - The ValidateSet attribute and the ValidatePattern attribute cannot 
          pass named parameters.

        - Advanced functions cannot be used in transactions.

   
SEE ALSO
    about_Functions
    about_Functions_Advanced_Methods    
    about_Functions_Advanced_Parameters 
    about_Functions_CmdletBindingAttribute
    about_Functions_OutputTypeAttribute
    Windows PowerShell Cmdlets (http://go.microsoft.com/fwlink/?LinkID=135279)



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