About Functions Advanced


Introduces advanced functions that act similar to cmdlets.


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 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
        [string] $Name

        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.