Export (0) Print
Expand All
Expand Minimize

about_Functions_OutputTypeAttribute

Updated: October 30, 2012

Applies To: Windows PowerShell 3.0

TOPIC
    about_Functions_OutputTypeAttribute

SHORT DESCRIPTION
    Describes an attribute that reports the type of object that the function
    returns.

LONG DESCRIPTION
    The OutputType attribute lists the .NET types of objects that the functions
    returns. You can use its optional ParameterSetName parameter to list different
    output types for each parameter set.

    The OutputType attribute is supported on simple and advanced functions. It is
    independent of the CmdletBinding attribute.

    The OutputType attribute provides the value of the OutputType property of the
    System.Management.Automation.FunctionInfo object that the Get-Command cmdlet
    returns.

    The OutputType attribute value is only a documentation note. It is not derived
    from the function code or compared to the actual function output. As such, the
    value might be inaccurate.


  SYNTAX
    The OutputType attribute of functions has the following syntax:
       
        [OutputType([<TypeLiteral>], ParameterSetName="<Name>")]
        [OutputType("<TypeNameString>", ParameterSetName="<Name>")]

    The ParameterSetName parameter is optional.


    You can list multiple types in the OutputType attribute.

        [OutputType([<Type1>],[<Type2>],[<Type3>])]

    You can use the ParameterSetName parameter to indicate that different
    parameter sets return different types.

        [OutputType([<Type1>], ParameterSetName="<Set1>","<Set2>")]
        [OutputType([<Type2>], ParameterSetName="<Set3>")]



    Place the OutputType attribute statements in the attributes list that precedes
    the Param statement.

    The following example shows the placement of the OutputType attribute in a
    simple function.

        function SimpleFunction2
        {
    [OutputType([<Type>])]
            Param ($Parameter1)

            <function body>
        }


    The following example shows the placement of the OutputType attribute in
    advanced functions.

       function AdvancedFunction1
       {
           [OutputType([<Type>])]
           Param (      
               [parameter(Mandatory=$true)]
               [String[]]
               $Parameter1  
           )     
                  
         <function body>
       }


       function AdvancedFunction2
       {
           [CmdletBinding(SupportsShouldProcess=<Boolean>)]
           [OutputType([<Type>])]
           Param (      
               [parameter(Mandatory=$true)]
               [String[]]
               $Parameter1  
           )     
                  
         <function body>
       }


EXAMPLES

    The following function uses the OutputType attribute to indicate that it returns
    a string value.

        function Send-Greeting
        {
          [OutputType([String])]   
          Param ($Name)

          Hello, $Name      
        }

    
    To see the resulting output type property, use the Get-Command cmdlet.

        PS C:\> (Get-Command Send-Greeting).OutputType

        Name                                               Type                                                                                                     
        ----                                               ----                                                                                                     
        System.String                                      System.String        

                                                                                    

    The following advanced function uses the OutputType attribute to indicate that 
    the function returns different types depending on the parameter set used in the
    function command.

       function Get-User
       {
           [CmdletBinding(DefaultParameterSetName="ID")]

           [OutputType("System.Int32", ParameterSetName="ID")]
           [OutputType([String], ParameterSetName="Name")]

           Param (      
               [parameter(Mandatory=$true, ParameterSetName="ID")]
               [Int[]]
               $UserID,

               [parameter(Mandatory=$true, ParameterSetName="Name")]
               [String[]]
               $UserName
           )     
                  
         <function body>
       }


    The following example demonstrates that the output type property value
    displays the value of the OutputType attribute, even when it is inaccurate.

    The Get-Time function returns a string that contains the short form of
    the time in any DateTime object. However, the OutputType attribute reports
    that it returns a System.DateTime object.

        function Get-Time
        { 
            [OutputType([DateTime])]
            Param
            (
               [parameter(Mandatory=$true)]
               [Datetime]$DateTime       
            )
            $DateTime.ToShortTimeString()
        }  
  
        
    The Get-Type method confirms that the function returns a string.

        PS C:\> (Get-Time -DateTime (Get-Date)).Gettype().FullName
        System.String


    However, the OutputType property, which gets its value from the OutputType
    attribute, reports that the function returns a DateTime object.

        PS C:\> (Get-Command Get-Time).OutputType

        Name                                      Type                                                                                                     
        ----                                      ----                                                                                                     
        System.DateTime                           System.DateTime 


NOTES
    The value of the OutputType property of a FunctionInfo object is an array of 
    System.Management.Automation.PSTypeName objects, each of which have Name and
    Type properties.

    To get only the name of each output type, use a command with the following 
    format.

        (Get-Command Get-Time).OutputType | ForEach {$_.Name}
    
    The value of the OutputType property can be null. Use a null value when 
    the output is a not a .NET type, such as a WMI object or a formatted view
    of an object.

SEE ALSO
    about_Functions
    about_Functions_Advanced
    about_Functions_Advanced_Methods
    about_Functions_Advanced_Parameters
    about_Functions_CmdletBindingAttribute 



Was this page helpful?
(1500 characters remaining)
Thank you for your feedback
Show:
© 2014 Microsoft