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about_Properties

Updated: August 9, 2012

Applies To: Windows PowerShell 2.0, Windows PowerShell 3.0

TOPIC
    about_Properties

SHORT DESCRIPTION
    Describes how to use object properties in Windows PowerShell. 

LONG DESCRIPTION
    Windows PowerShell uses structured collections of information called
    objects to represent the items in data stores or the state of the computer.
    Typically, you work with object that are part of the Microsoft .NET
    Framework, but you can also create custom objects in Windows PowerShell.

    The association between an item and its object is very close. When you
    change an object, you usually change the item that it represents. For 
    example, when you get a file in Windows PowerShell, you do not get the 
    actual file. Instead, you get a FileInfo object that represents the file. 
    When you change the FileInfo object, the file changes too.

    Most objects have properties. Properties are the data that is associated 
    with an object. Different types of object have different properties. For 
    example, a FileInfo object, which represents a file, has an IsReadOnly 
    property that contains $True if the file the read-only attribute and $False
    if it does not. A DirectoryInfo object, which represents a file system 
    directory, has a Parent property that contains the path to the parent
    directory.

 OBJECT PROPERTIES

     To get the properties of an object, use the Get-Member cmdlet. For 
     example, to get the properties of a FileInfo object, use the Get-ChildItem 
     cmdlet to get the FileInfo object that represents a file. Then, use a 
     pipeline operator (|) to send the FileInfo object to Get-Member. The 
     following command gets the PowerShell.exe file and sends it to Get-Member. 
     The $Pshome automatic variable contains the path of the Windows PowerShell 
     installation directory.

         Get-ChildItem $pshome\PowerShell.exe | Get-Member


     The output of the command lists the members of the FileInfo object. 
     Members include both properties and methods. When you work in 
     Windows PowerShell, you have access to all the members of the objects.


     To get only the properties of an object and not the methods, use the 
     MemberType parameter of the Get-Member cmdlet with a value of "property", 
     as shown in the following example.

         Get-ChildItem $pshome\PowerShell.exe | Get-Member -MemberType property

            TypeName: System.IO.FileInfo
        
         Name              MemberType Definition
         ----              ---------- ----------
         Attributes        Property   System.IO.FileAttributes Attributes {get;set;}
         CreationTime      Property   System.DateTime CreationTime {get;set;}
         CreationTimeUtc   Property   System.DateTime CreationTimeUtc {get;set;}
         Directory         Property   System.IO.DirectoryInfo Directory {get;}
         DirectoryName     Property   System.String DirectoryName {get;}
         Exists            Property   System.Boolean Exists {get;}
         Extension         Property   System.String Extension {get;}
         FullName          Property   System.String FullName {get;}
         IsReadOnly        Property   System.Boolean IsReadOnly {get;set;}
         LastAccessTime    Property   System.DateTime LastAccessTime {get;set;}
         LastAccessTimeUtc Property   System.DateTime LastAccessTimeUtc {get;set;}
         LastWriteTime     Property   System.DateTime LastWriteTime {get;set;}
         LastWriteTimeUtc  Property   System.DateTime LastWriteTimeUtc {get;set;}
         Length            Property   System.Int64 Length {get;}
         Name              Property   System.String Name {get;}

     After you find the properties, you can use them in your Windows PowerShell 
     commands.


PROPERTY VALUES

     Although every object of a specific type has the same properties, the 
     values of those properties describe the particular object. For example, 
     every FileInfo object has a CreationTime property, but the value of that
     property differs for each file.


     The most common way to get the values of the properties of an object is to 
     use the dot method. Type a reference to the object, such as a variable 
     that contains the object, or a command that gets the object. Then, type a 
     dot (.) followed by the property name.


     For example, the following command displays the value of the CreationTime 
     property of the PowerShell.exe file. The Get-ChildItem command returns a 
     FileInfo object that represents the PowerShell.exe file. The command is 
     enclosed in parentheses to make sure that it is executed before any 
     properties are accessed. The Get-ChildItem command is followed by a dot 
     and the name of the CreationTime property, as follows:

         C:\PS> (Get-ChildItem $pshome\PowerShell.exe).creationtime
         Tuesday, March 18, 2008 12:07:52 AM


     You can also save an object in a variable and then get its properties by 
     using the dot method, as shown in the following example:

         C:\PS> $a = Get-ChildItem $pshome\PowerShell.exe
         C:\PS> $a.CreationTime
         Tuesday, March 18, 2008 12:07:52 AM


     You can also use the Select-Object and Format-List cmdlets to display the 
     property values of an object. Select-Object and Format-List each have a 
     Property parameter. You can use the Property parameter to specify one or 
     more properties and their values. Or, you can use the wildcard 
     character (*) to represent all the properties.


     For example, the following command displays the values of all the 
     properties of the PowerShell.exe file.  
 
 
         C:\PS> Get-ChildItem $pshome\PowerShell.exe | Format-List -property *

         PSPath            : Microsoft.PowerShell.Core\FileSystem::C:\Windows\system32\WindowsPowerShell\v1.0\PowerShell.exe
         PSParentPath      : Microsoft.PowerShell.Core\FileSystem::C:\Windows\system32\WindowsPowerShell\v1.0
         PSChildName       : PowerShell.exe
         PSDrive           : C
         PSProvider        : Microsoft.PowerShell.Core\FileSystem
         PSIsContainer     : False
         VersionInfo       : File:             C:\Windows\system32\WindowsPowerShell\v1.0\PowerShell.exe
                             InternalName:     POWERSHELL
                             OriginalFilename: PowerShell.EXE.MUI
                             File Version:      6.1.6570.1 (fbl_srv_PowerShell(nigels).070711-0102)
                             FileDescription:  PowerShell.EXE
                             Product:          Microsoft® Windows® Operating System
                             ProductVersion:   6.1.6570.1
                             Debug:            False
                             Patched:          False
                             PreRelease:       False
                             PrivateBuild:     True
                             SpecialBuild:     False
                             Language:         English (United States)

         BaseName          : PowerShell
         Mode              : -a---
         Name              : PowerShell.exe
         Length            : 160256
         DirectoryName     : C:\Windows\system32\WindowsPowerShell\v1.0
         Directory         : C:\Windows\system32\WindowsPowerShell\v1.0
         IsReadOnly        : False
         Exists            : True
         FullName          : C:\Windows\system32\WindowsPowerShell\v1.0\PowerShell.exe
         Extension         : .exe
         CreationTime      : 3/18/2008 12:07:52 AM
         CreationTimeUtc   : 3/18/2008 7:07:52 AM
         LastAccessTime    : 3/19/2008 8:13:58 AM
         LastAccessTimeUtc : 3/19/2008 3:13:58 PM
         LastWriteTime     : 3/18/2008 12:07:52 AM
         LastWriteTimeUtc  : 3/18/2008 7:07:52 AM
         Attributes        : Archive
        
 
 STATIC PROPERTIES
    You can use the static properties of .NET classes in Windows
    PowerShell. Static properties are properties of class, 
    unlike standard properties, which are properties of an
    object.

    To get the static properties of an class, use the Static
    parameter of the Get-Member cmdlet.

    For example, the following command gets the static
    properties of the System.DateTime class.

        Get-Date | Get-Member -MemberType Property -Static

           TypeName: System.DateTime

        Name     MemberType Definition
        ----     ---------- ----------
        MaxValue Property   static datetime MaxValue {get;}
        MinValue Property   static datetime MinValue {get;}
        Now      Property   datetime Now {get;}
        Today    Property   datetime Today {get;}
        UtcNow   Property   datetime UtcNow {get;}


    To get the value of a static property, use the following 
    syntax.

        [<ClassName>]::<Property>

    For example, the following command gets the value of the
    UtcNow static property of the System.DateTime class.
    
        [System.DateTime]::UtcNow



 PROPERTIES OF SCALAR OBJECTS AND COLLECTIONS

    The properties of one ("scalar") object of a particular type
    are often different from the properties of a collection of objects 
    of the same type.

    For example, every service has as DisplayName property, but
    a collection of services does not have a DisplayName property. 
    Similarly, all collections have a Count property that tells how
    many objects are in the collection, but individual objects do not
    have a Count property.

    Beginning in Windows PowerShell 3.0, Windows PowerShell tries
    to prevent scripting errors that result from the differing
    properties of scalar objects and collections. 

    --  If you submit a collection, but request a property
        that exists only on single ("scalar") objects, Windows 
        PowerShell returns the value of that property for every object
        in the collection.

    --  If you request the Count or Length property of zero objects
        or of one object, Windows PowerShell returns the correct value.

    If the property exists on the individual objects and on the 
    collection, Windows PowerShell does not alter the result.

    This feature also works on methods of scalar objects and 
    collections. For more information, see about_Methods.


    EXAMPLES

    For example, each service has a DisplayName property. The 
    following command gets the value of the DisplayName property
    of the Audiosrv service.

        PS C:\>(Get-Service Audiosrv).DisplayName
        Windows Audio

    However, a collection or array of services does not have a
    DisplayName. The following command tries to get the DisplayName 
    property of all services in Windows PowerShell 2.0.

        PS C:\>(Get-Service).DisplayName
        PS C:\>

    Beginning in Windows PowerShell 3.0, the same command returns 
    the value of the DisplayName property of every service that 
    Get-Service returns.

        PS C:\>(Get-Service).DisplayName
        Application Experience
        Application Layer Gateway Service
        Windows All-User Install Agent
        Application Identity
        Application Information
        ...

    Conversely, a collection of two or more services has a Count
    property, which contains the number of objects in the collection.

        PS C:\>(Get-Service).Count
        176

    Individual services do not have a Count or Length property, as
    shown in this command in Windows PowerShell 2.0.

        PS C:\>(Get-Service Audiosrv).Count
        PS C:\>
        
    Beginning in Windows PowerShell 3.0, the command returns the
    correct Count value.

        PS C:\>(Get-Service Audiosrv).Count
        1



SEE ALSO
    about_Methods
    about_Objects
    Get-Member
    Select-Object
    Format-List



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