about_functions_cmdletbindingattribute | Easy Powershell 2.0 Reference

TOPIC
about_functions_CmdletBindingAttribute

SHORT DESCRIPTION
Describes an attribute that declares a Function that acts similar to a
compiled cmdlet.

LONG DESCRIPTION
    When you write Functions, you can add the CmdletBinding attribute so that
    Windows PowerShell will bind the parameters of the Function in the same
    way that it binds the parameters of compiled cmdlets. When this attribute
    is declared, Windows PowerShell also sets the $PSCmdlet automatic Variable.

    When you use cmdlet binding, unknown parameters and positional arguments
    that have no matching positional parameters cause parameter binding to
    fail. Also, a Function or script with cmdlet binding does not use the
    $args Variable.

Note: Compiled cmdlets use the required Cmdlet attribute, which is similar
to the CmdletBinding attribute that is described in this topic.

    The following example shows the outline of a Function that specifies all
    the optional arguments of the CmdletBinding attribute. A brief description
    of each argument follows this example.

        {
         [CmdletBinding(SupportsShouldProcess=<Boolean>,
                     ConfirmImpact=<String>,
                     DefaultParameterSetName=<String>)]

         Param ($Parameter1)
         Begin{}
         Process{}
         End{}
        }

SupportsShouldProcess

     When the SupportsShouldProcess argument is set to true, it indicates that
     the Function supports calls to the ShouldProcess method, which is used to
     prompt the user for feedback before the Function makes a change to the
     system. When this argument is specified, the Confirm and WhatIf
     parameters are enabled for the Function.

     For more information about confirmation requests, see “Requesting
     Confirmation” in the MSDN (Microsoft Developer Network) library at
     http://go.microsoft.com/fwlink/?LinkId=136658.

DefaultParameterSetName

     The DefaultParameterSetName argument specifies the name of the parameter
     set that Windows PowerShell will attempt to use when it cannot determine
     which parameter set to use. You can avoid this issue by making the
     unique parameter of each parameter set a mandatory parameter.

ConfirmImpact

     The ConfirmImpact argument specifies when the action of the Function
     should be confirmed by a call to the ShouldProcess method. The call to
     the ShouldProcess method displays a confirmation prompt only when the
     ConfirmImpact argument is equal to or greater than the value of the
     $ConfirmPreference preference Variable. (The default value of the
     argument is Medium.) Specify this argument only when the
     SupportsShouldProcess argument is also specified.