Add-Member

Add-Member [-MemberType] {<AliasProperty> | <CodeProperty> | <Property> | <NoteProperty> | <ScriptProperty> | <Properties> | <PropertySet> | <Method> | <CodeMethod> | <ScriptMethod> | <Methods> | <ParameterizedProperty> | <MemberSet> | <Event> | <All>} [-Name] <string> -InputObject <psobject> [[-Value] <Object>] [[-SecondValue] <Object>] [-Force] [-PassThru] [<CommonParameters>]

C:\PS>$a = (get-childitem)[0]

C:\PS> $a | add-member -membertype noteproperty -name Status -value done

C:\PS> $a | get-member -type noteproperty

TypeName: System.IO.DirectoryInfo

Name          MemberType   Definition
----          ----------   ----------
PSChildName   NoteProperty System.String PSChildName=Co
PSDrive       NoteProperty System.Management.Automation
PSIsContainer NoteProperty System.Boolean PSIsContainer
PSParentPath  NoteProperty System.String PSParentPath=M
PSPath        NoteProperty System.String PSPath=Microso
PSProvider    NoteProperty System.Management.Automation
Status        NoteProperty System.String Status=done


Description
-----------
These commands add the Status note property to a DirectoryInfo object returned by Get-ChildItem and assigns it a value of "done". 

The first command gets the first object that Get-Childitem returns (index 0).

The second command adds the note property.

The third command uses a pipeline operator (|) to send the updated object to the Get-Member cmdlet. The output shows that the property has been added.

C:\PS>$a = (get-childitem)[0]

C:\PS> $a | add-member -membertype aliasproperty -name FileLength -value Length 

C:\PS> $a.filelength

These commands add the FileLength alias property to a DirectoryInfo object returned by Get-ChildItem. The new property is an alias for the Length property. 

The first command gets the first object that Get-Childitem returns (index 0).

The second command adds the alias property.

The third command returns the value of the new FileLength property.

C:\PS>$a = "a string"

C:\PS> $a = $a | add-member -membertype noteproperty -name StringUse -value Display -passthru

C:\PS> $a.StringUse

These commands add the StringUse a property to a string. Because the string is not a PSObject object, you must include the PassThru parameter in the command to save the extended string in the variable. The last command in the example displays the new property.

C:\PS>$a = "this is a string"

C:\PS> $a = add-member -inputobject $a -membertype scriptmethod -name words `
-value {$this.split()} -passthru

C:\PS> $a.words()

These commands add a script method to a string object. The script method exposes the Split() method of the System.String .NET Framework Class Library class to make it convenient to return the individual words in a string by calling a method named "Words" on the string object. Note that the PassThru parameter is specified to force Add-Member to return the extended string object as output to be stored in the $a variable.

C:\PS>$event = get-eventlog -logname system -newest 1

C:\PS> $event.TimeWritten | get-member

C:\PS> add-member -inputobject $event -membertype aliasproperty -name When `
-value TimeWritten -secondvalue System.String

C:\PS> $event.When | get-member

These commands add an AliasProperty to an EventLogEntry object returned by the Get-EventLog cmdlets. The AliasProperty is named "When" and is an alias for the TimeWritten property of the object. The SecondValue parameter is used to specify that the property value should be converted to type System.String when accessed by using the AliasProperty; the TimeWritten property is a DateTime object.

The first command uses the Get-EventLog cmdlet to retrieve the most recent event from the System event log and stores it in the $event variable. 

The second command accesses the TimeWritten property of that event and pipes it to the Get-Member cmdlet to demonstrate that the property is a DateTime type. Add-Member is then used to add an AliasProperty member to the instance of the EventLogEntry object stored in the $event variable. The Name parameter is used to set the name of the new member to "When" and the Value parameter is used to specify that it is an alias for the TimeWritten property. The SecondValue parameter is used to indicate that, when this new member is used, the value it returns should be cast from its original System.DateTime type to a System.String type. 

The third command accesses the new member and pipes it to the Get-Member cmdlet to confirm that it is of type System.String.

C:\PS>function Copy-Property ($From, $To)

{
  foreach ($p in Get-Member -InputObject $From -MemberType Property)
  {
     Add-Member -InputObject $To -MemberType NoteProperty -Name $p.Name 
     -Value $From.$($p.Name) -Force

     $To.$($p.Name) = $From.$($p.Name)
   }
}

This function copies all of the properties of one object to another object.

The first command in the function declares the function name and lists its parameters. 

The Foreach loop uses the Get-Member cmdlet to get each of the properties of the From object. The commands within the Foreach loop are performed in series on each of the properties.

The Add-Member command adds the property of the From object to the To object as a NoteProperty. It uses the Force parameter to let the command add members with the same member name.

The last command in the function gives the new property the same name as the original property.