about_Types.ps1xml

Article
08/07/2024

Short description

Explains how to use Types.ps1xml files to extend the types of objects that are used in PowerShell.

Long description

Extended type data defines additional properties and methods ("members") of object types in PowerShell. There are two techniques for adding extended type data to a PowerShell session.

Types.ps1xml file: An XML file that defines extended type data.
Update-TypeData: A cmdlet that reloads Types.ps1xml files and defines extended data for types in the current session.

This topic describes Types.ps1xml files. For more information about using the Update-TypeData cmdlet to add dynamic extended type data to the current session see Update-TypeData.

About extended type data

Extended type data defines additional properties and methods ("members") of object types in PowerShell. You can extend any type that is supported by PowerShell and use the added properties and methods in the same way that you use the properties that are defined on the object types.

For example, PowerShell adds a DateTime property to all System.DateTime objects, such as the ones that the Get-Date cmdlet returns.

(Get-Date).DateTime

Sunday, January 29, 2012 9:43:57 AM

You won't find the DateTime property in the description of the System.DateTime structure, because PowerShell adds the property and it is visible only in PowerShell.

PowerShell internally defines a default set of extended types. This type information is loaded in every PowerShell session at startup. The DateTime property is part of this default set. Prior to PowerShell 6, the type definitions were stored the Types.ps1xml file in the PowerShell installation directory ($PSHOME).

Adding extended type data to PowerShell

There are three sources of extended type data in PowerShell sessions.

Extended type data is defined by PowerShell and loaded automatically into every PowerShell session. Beginning with PowerShell 6, this information is compiled into PowerShell and is no longer shipped in a Types.ps1xml file.
The Types.ps1xml files that modules export are loaded when the module is imported into the current session.
Extended type data that is defined by using the Update-TypeData cmdlet is added only to the current session. It is not saved in a file.

In the session, the extended type data from the three sources is applied to objects in the same way and is available on all objects of the specified types.

The TypeData cmdlets

The following cmdlets are included in the Microsoft.PowerShell.Utility module in PowerShell 3.0 and later.

Get-TypeData: Gets extended type data in the current session.
Update-TypeData: Reloads Types.ps1xml files. Adds extended type data to the current session.
Remove-TypeData: Removes extended type data from the current session.

For more information about these cmdlets, see the help topic for each cmdlet.

Built-in Types.ps1xml files

The Types.ps1xml files in the $PSHOME directory are added automatically to every session.

The Types.ps1xml file in the PowerShell installation directory ($PSHOME) is an XML-based text file that lets you add properties and methods to the objects that are used in PowerShell. PowerShell has built-in Types.ps1xml files that add several elements to the .NET types, but you can create additional Types.ps1xml files to further extend the types.

For example, by default, array objects (System.Array) have a Length property that lists the number of objects in the array. However, because the name Length does not clearly describe the property, PowerShell adds an alias property named Count that displays the same value. The following XML adds the Count property to the System.Array type.

<Type>
  <Name>System.Array</Name>
  <Members>
    <AliasProperty>
      <Name>Count</Name>
      <ReferencedMemberName>
        Length
      </ReferencedMemberName>
    </AliasProperty>
  </Members>
</Type>

To get the new AliasProperty, use a Get-Member command on any array, as shown in the following example.

Get-Member -InputObject (1,2,3,4)

The command returns the following results.

Name       MemberType    Definition
----       ----------    ----------
Count      AliasProperty Count = Length
Address    Method        System.Object& Address(Int32)
Clone      Method        System.Object Clone()
CopyTo     Method        System.Void CopyTo(Array array, Int32 index):
Equals     Method        System.Boolean Equals(Object obj)
Get        Method        System.Object Get(Int32)
# ...

As a result, you can use either the Count property or the Length property of arrays in PowerShell. For example:

(1, 2, 3, 4).count
4

(1, 2, 3, 4).length
4

Creating new Types.ps1xml files

The .ps1xml files that are installed with PowerShell are digitally signed to prevent tampering because the formatting can include script blocks. Therefore, to add a property or method to a .NET type, create your own Types.ps1xml files, and then add them to your PowerShell session.

To create a new file, start by copying an existing Types.ps1xml file. The new file can have any name, but it must have a .ps1xml file name extension. You can place the new file in any directory that is accessible to PowerShell, but it is useful to place the files in the PowerShell installation directory ($PSHOME) or in a subdirectory of the installation directory.

When you have saved the new file, use the Update-TypeData cmdlet to add the new file to your PowerShell session. If you want your types to take precedence over the built-in types that are defined, use the PrependData parameter of the Update-TypeData cmdlet. Update-TypeData affects only the current session. To make the change to all future sessions, export the console, or add the Update-TypeData command to your PowerShell profile.

Types.ps1xml and Add-Member

The Types.ps1xml files add properties and methods to all the instances of the objects of the specified .NET type in the affected PowerShell session. However, if you need to add properties or methods only to one instance of an object, use the Add-Member cmdlet.

For more information, see Add-Member.

Example: Adding an Age member to FileInfo objects

This example shows how to add an Age property to System.IO.FileInfo objects. The age of a file is the difference between its creation time and the current time in days.

Because the Age property is calculated by using a script block, find a <ScriptProperty> tag to use as a model for the new Age property.

Save the follow XML code to the file $PSHOME\MyTypes.ps1xml.

<?xml version="1.0" encoding="utf-8" ?>
<Types>
  <Type>
    <Name>System.IO.FileInfo</Name>
    <Members>
      <ScriptProperty>
        <Name>Age</Name>
        <GetScriptBlock>
          ((Get-Date) - ($this.CreationTime)).Days
        </GetScriptBlock>
      </ScriptProperty>
    </Members>
  </Type>
</Types>

Run Update-TypeData to add the new Types.ps1xml file to the current session. The command uses the PrependData parameter to place the new file in a precedence order higher than the original definitions.

For more information about Update-TypeData, see Update-TypeData.

Update-Typedata -PrependPath $PSHOME\MyTypes.ps1xml

To test the change, run a Get-ChildItem command to get the PowerShell.exe file in the $PSHOME directory, and then pipe the file to the Format-List cmdlet to list all of the properties of the file. As a result of the change, the Age property appears in the list.

Get-ChildItem $PSHOME\pwsh.exe | Select-Object Age

The XML in Types.ps1xml files

The full schema definition can be found in Types.xsd in the PowerShell source code repository on GitHub.

The <Types> tag encloses all of the types that are defined in the file. There should be only one <Types> tag.

Each .NET type mentioned in the file should be represented by a <Type> tag.

The type tags must contain the following tags:

<Name>: Encloses the name of the affected .NET type.

<Members>: Encloses the tags for the new properties and methods that are defined for the .NET type.

Any of the following member tags can be inside the <Members> tag.

AliasProperty

Defines a new name for an existing property.

The <AliasProperty> tag must have a <Name> tag that specifies the name of the new property and a <ReferencedMemberName> tag that specifies the existing property.

For example, the Count alias property is an alias for the Length property of array objects.

<Type>
  <Name>System.Array</Name>
  <Members>
    <AliasProperty>
      <Name>Count</Name>
      <ReferencedMemberName>Length</ReferencedMemberName>
    </AliasProperty>
  </Members>
</Type>

CodeMethod

References a static method of a .NET class.

The <CodeMethod> tag must have a <Name> tag that specifies the name of the new method and a <CodeReference> tag that specifies the code in which the method is defined.

For example, the ToString method is the name of the Microsoft.PowerShell.ToStringCodeMethods code definition.

  <Type>
    <Name>System.Xml.XmlNode</Name>
    <Members>
      <CodeMethod>
        <Name>ToString</Name>
        <CodeReference>
          <TypeName>Microsoft.PowerShell.ToStringCodeMethods</TypeName>
          <MethodName>XmlNode</MethodName>
        </CodeReference>
      </CodeMethod>
    </Members>
  </Type>

CodeProperty

References a static method of a .NET class.

The <CodeProperty> tag must have a <Name> tag that specifies the name of the new property and a <GetCodeReference> tag that specifies the code in which the property is defined.

For example, the Mode property of System.IO.DirectoryInfo objects is a code property defined in the PowerShell FileSystem provider.

<Type>
  <Name>System.IO.DirectoryInfo</Name>
  <Members>
    <CodeProperty>
      <Name>Mode</Name>
      <GetCodeReference>
        <TypeName>
          Microsoft.PowerShell.Commands.FileSystemProvider
        </TypeName>
        <MethodName>Mode</MethodName>
      </GetCodeReference>
    </CodeProperty>
  </Members>
</Type>

MemberSet

Defines a collection of members (properties and methods).

The <MemberSet> tags appear within the primary <Members> tags. The tags must enclose a <Name> tag surrounding the name of the member set and a secondary <Members> tag that surround the members (properties and methods) in the set. Any of the tags that create a property (such as <NoteProperty> or <ScriptProperty>) or a method (such as <Method> or <ScriptMethod>) can be members of the set.

In Types.ps1xml files, the <MemberSet> tag is used to define the default views of the .NET objects in PowerShell. In this case, the name of the member set (the value within the <Name> tags) is always PsStandardMembers, and the names of the properties (the value of the <Name> tag) are one of the following:

DefaultDisplayProperty: A single property of an object.
DefaultDisplayPropertySet: One or more properties of an object.
DefaultKeyPropertySet: One or more key properties of an object. A key property identifies instances of property values, such as the ID number of items in a session history.

For example, the following XML defines the default display of services (System.ServiceProcess.ServiceController objects) that are returned by the Get-Service cmdlet. It defines a member set named PsStandardMembers that consists of a default property set and a default display property. It defines the default property set as the Status, Name, and DisplayName properties. It defines the default display property as Name.

<Type>
  <Name>System.ServiceProcess.ServiceController</Name>
  <Members>
    <MemberSet>
      <Name>PSStandardMembers</Name>
      <Members>
        <PropertySet>
          <Name>DefaultDisplayPropertySet</Name>
          <ReferencedProperties>
            <Name>Status</Name>
            <Name>Name</Name>
            <Name>DisplayName</Name>
          </ReferencedProperties>
        </PropertySet>
        <NoteProperty>
          <Name>DefaultDisplayProperty</Name>
          <Value>Name</Value>
        </NoteProperty>
      </Members>
    </MemberSet>
  </Members>
</Type>

<Method>: References a native method of the underlying object.

<Methods>: A collection of the methods of the object.

NoteProperty

Defines a property with a static value.

The <NoteProperty> tag must have a <Name> tag that specifies the name of the new property and a <Value> tag that specifies the value of the property.

For example, the following XML creates a Status property for System.IO.DirectoryInfo objects. The value of the Status property is always Success.

<Type>
  <Name>System.IO.DirectoryInfo</Name>
  <Members>
    <NoteProperty>
      <Name>Status</Name>
      <Value>Success</Value>
    </NoteProperty>
  </Members>
</Type>

PropertySet

Properties that take arguments and return a value.

<Properties>: A collection of the properties of the object.

<Property>: A property of the base object.

<PropertySet>: Defines a collection of properties of the object.

The <PropertySet> tag must have a <Name> tag that specifies the name of the property set and a <ReferencedProperty> tag that specifies the properties. The names of the properties are enclosed in <Name> tag.

In Types.ps1xml, <PropertySet> tags are used to define sets of properties for the default display of an object. You can identify the default displays by the value PsStandardMembers in the <Name> tag of a <MemberSet> tag.

For example, the following XML creates a PropertySet named DefaultDisplayPropertySet with three ReferencedProperties.

<Type>
  <Name>System.ServiceProcess.ServiceController</Name>
  <Members>
    <MemberSet>
      <Name>PSStandardMembers</Name>
      <Members>
        <PropertySet>
          <Name>DefaultDisplayPropertySet</Name>
          <ReferencedProperties>
            <Name>Status</Name>
            <Name>Name</Name>
            <Name>DisplayName</Name>
          </ReferencedProperties>
        </PropertySet>
      </Members>
    </MemberSet>
  </Members>
</Type>

ScriptMethod

Defines a method whose value is the output of a script.

The <ScriptMethod> tag must have a <Name> tag that specifies the name of the new method and a <Script> tag that encloses the script block that returns the method result.

For example, the ConvertToDateTime and ConvertFromDateTime methods of management objects (System.System.Management.ManagementObject) are script methods that use the ToDateTime and ToDmtfDateTime static methods of the System.Management.ManagementDateTimeConverter class.

<Type>
 <Name>System.Management.ManagementObject</Name>
 <Members>
 <ScriptMethod>
   <Name>ConvertToDateTime</Name>
   <Script>
   [System.Management.ManagementDateTimeConverter]::ToDateTime($args[0])
   </Script>
 </ScriptMethod>
 <ScriptMethod>
   <Name>ConvertFromDateTime</Name>
   <Script>
   [System.Management.ManagementDateTimeConverter]::ToDmtfDateTime($args[0])
   </Script>
 </ScriptMethod>
 </Members>
</Type>

ScriptProperty

Defines a property whose value is the output of a script.

The <ScriptProperty> tag must have a <Name> tag that specifies the name of the new property and a <GetScriptBlock> tag that encloses the script block that returns the property value.

For example, the VersionInfo property of the System.IO.FileInfo object is a script property that results from using the FullName property of the GetVersionInfo static method of System.Diagnostics.FileVersionInfo objects.

<Type>
  <Name>System.IO.FileInfo</Name>
  <Members>
    <ScriptProperty>
      <Name>VersionInfo</Name>
      <GetScriptBlock>
      [System.Diagnostics.FileVersionInfo]::GetVersionInfo($this.FullName)
      </GetScriptBlock>
    </ScriptProperty>
  </Members>
</Type>

For more information, see the Windows PowerShell Software Development Kit (SDK).

Update-TypeData

To load your Types.ps1xml files into a PowerShell session, run the Update-TypeData cmdlet. If you want the types in your file to take precedence over types in the built-in Types.ps1xml file, add the PrependData parameter of Update-TypeData. Update-TypeData affects only the current session. To make the change to all future sessions, export the session, or add the Update-TypeData command to your PowerShell profile.

Exceptions that occur in properties, or from adding properties to an Update-TypeData command, do not report errors to StdErr. This is to suppress exceptions that would occur in many common types during formatting and outputting. If you are getting .NET properties, you can work around the suppression of exceptions by using method syntax instead, as shown in the following example:

"hello".get_Length()

Note that method syntax can only be used with .NET properties. Properties that are added by running the Update-TypeData cmdlet cannot use method syntax.

Signing a Types.ps1xml file

To protect users of your Types.ps1xml file, you can sign the file using a digital signature. For more information, see about_Signing.

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