about_Functions_Advanced_Methods

TOPIC
	about_Functions_Advanced_Methods

SHORT DESCRIPTION
	Describes how functions that specify the CmdletBinding attribute can use
	the methods and properties that are available to compiled cmdlets.

LONG DESCRIPTION
	Functions that specify the CmdletBinding attribute can access a number of 
	methods and properties through the $pscmdlet variable. These methods 
	include the following methods:


		- Input-processing methods that compiled cmdlets use to do their work.

		- The ShouldProcess and ShouldContinue methods that are used to get 
		user feedback before an action is performed.

		- The ThrowTerminatingError method for generating error records.

		- Several Write methods that return different types of output.

		- Several Write methods that return different types of output. 


	All the methods and properties of the PSCmdlet class are available to 
	advanced functions. For more information about these methods and 
	properties, see System.Management.Automation.PSCmdlet in the MSDN 
	(Microsoft Developer Network) library at 
	http://go.microsoft.com/fwlink/?LinkId=142139.


  Input Processing Methods

	The methods described in this section are referred to as the input 
	processing methods. For functions, these three methods are represented
	by the Begin, Process, and End blocks of the function. Each function 
	must include one or more of these blocks. The Windows PowerShell runtime
	uses the code within these blocks when it is running a function. (These
	blocks are also available to functions that do not use the CmdletBinding
	attribute.)


	Begin
	This block is used to provide optional one-time preprocessing for the 
	function. The Windows PowerShell runtime uses the code in this block one
	time for each instance of the function in the pipeline.


	Process
	This block is used to provide record-by-record processing for the 
	function. This block might be used any number of times, or not at all,
	depending on the input to the function. For example, if the function is
	the first command in the pipeline, the Process block will be used one 
	time. If the function is not the first command in the pipeline, the 
	Process block is used one time for every input that the function 
	receives from the pipeline. If there is no pipeline input, the Process 
	block is not used.

	This block must be defined if a function parameter is set to accept 
	pipeline input. If this block is not defined and the parameter accepts
	input from the pipeline, the function will miss the values that are 
	passed to the function through the pipeline. 

	Also, when the function supports confirmation requests (when the 
	SupportsShouldProcess parameter of the Parameter attribute is set to 
	$True), the call to the ShouldProcess method must be made from within
	the Process block.

	End
	This block is used to provide optional one-time post-processing for 
	the function.

	The following example shows the outline of a function that contains a
	Begin block for one-time preprocessing, a Process block for multiple 
	record processing, and an End block for one-time post-processing.

		Function Test-ScriptCmdlet
		{
			[CmdletBinding(SupportsShouldProcess=$True)] 
			Param ($Parameter1)
			Begin{}
			Process{}
			End{}
	}


  Confirmation Methods

	ShouldProcess
	This method is called to request confirmation from the user before the 
	function performs an action that would change the system. The function 
	can continue based on the Boolean value returned by the method. This 
	method can be called only from within the Process{} block of the 
	function. And, the CmdletBinding attribute must declare that the 
	function supports ShouldProcess (as shown in the previous example).

	For more information about this method, see 
	System.Management.Automation.Cmdlet.ShouldProcess in the MSDN library at 
	http://go.microsoft.com/fwlink/?LinkId=142142.

	For more information about how to request confirmation, see 
	"Requesting Confirmation" in the MSDN library at 
	http://go.microsoft.com/fwlink/?LinkID=136658.


	ShouldContinue
	This method is called to request a second confirmation message. It 
	should be called when the ShouldProcess method returns $true. For more
	information about this method, see 
	System.Management.Automation.Cmdlet.ShouldContinue in the MSDN library
	at http://go.microsoft.com/fwlink/?LinkId=142143.


  Error Methods

	Functions can call two different methods when errors occur. When a 
	nonterminating error occurs, the function should call the WriteError 
	method, which is described in the "Write Methods" section. When a 
	terminating error occurs and the function cannot continue, it should call
	the ThrowTerminatingError method. You can also use the Throw statement for
	terminating errors and the Write-Error cmdlet for nonterminating errors.

	For more information, see System.Management.Automation.Cmdlet.
	ThrowTerminatingError in the MSDN libray at 
	http://go.microsoft.com/fwlink/?LinkId=142144.


  Write Methods

	A function can call the following methods to return different types of 
	output. Notice that not all the output goes to the next command in the 
	pipeline. You can also use the various Write cmdlets, such as 
	Write-Error.


	WriteCommandDetail
	For information about the WriteCommandDetails method, see 
	System.Management.Automation.Cmdlet.WriteCommandDetail in the MSDN 
	library at http://go.microsoft.com/fwlink/?LinkId=142155.


	WriteDebug
	To provide information that can be used to troubleshoot a function, 
	make the function call the WriteDebug method. This displays debug 
	messages to the user. For more information, see 
	System.Management.Automation.Cmdlet.WriteDebug in the MSDN library
	at http://go.microsoft.com/fwlink/?LinkId=142156.


	WriteError
	Functions should call this method when nonterminating errors occur and
	the function is designed to continue processing records. For more 
	information, see System.Management.Automation.Cmdlet.WriteError in the 
	MSDN library at http://go.microsoft.com/fwlink/?LinkId=142157.

	Note: If a terminating error occurs, the function should call the 
			ThrowTerminatingError method. 


	WriteObject
	This method allows the function to send an object to the next command in 
	the pipeline. In most cases, this is the method to use when the function
	returns data. For more information, see 
	System.Management.Automation.PSCmdlet.WriteObject in the MSDN library at
	http://go.microsoft.com/fwlink/?LinkId=142158.


	WriteProgress
	For functions whose actions take a long time to complete, this method 
	allows the function to call the WriteProgress method so that progress
	information is displayed. For example, you can display the percent 
	completed. For more information, see 
	System.Management.Automation.PSCmdlet.WriteProgress in the MSDN library
	at http://go.microsoft.com/fwlink/?LinkId=142160.


	WriteVerbose
	To provide detailed information about what the function is doing, make 
	the function call the WriteVerbose method to display verbose messages to
	the user. By default, verbose messages are not displayed. For more 
	information, see System.Management.Automation.PSCmdlet.WriteVerbose
	in the MSDN library at http://go.microsoft.com/fwlink/?LinkId=142162.

	WriteWarning
	To provide information about conditions that may cause unexpected 
	results, make the function call the WriteWarning method to display 
	warning messages to the user. By default, warning messages are displayed.
	For more information, see 
	System.Management.Automation.PSCmdlet.WriteWarning in the MSDN library 
	at http://go.microsoft.com/fwlink/?LinkId=142164.

	Note: You can also display warning messages by configuring the 
			WarningPreference variable or by using the Verbose and Debug 
			command-line options.


  Other Methods and Properties

	For information about the other methods and properties that can be 
	accessed through the $PSCmdlet variable, see 
	System.Management.Automation.PSCmdlet in the MSDN library at
	http://go.microsoft.com/fwlink/?LinkId=142139. 

	For example, the ParameterSetName property allows you to see the parameter 
	set that is being used. Parameter sets allow you to create a function that 
	performs different tasks based on the parameters that are specified when 
	the function is run.


SEE ALSO
	about_Functions_Advanced
	about_Functions_CmdletBindingAttributes
	about_Functions_Advanced_Parameters