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

C:\PS>$a = dir c:\ps-test\test.txt

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

C:\PS> $a.Status

Done

Description
-----------
These commands add the Status note property with a value of "Done" to the object that represents the Test.txt file. 

The first command uses the Get-ChildItem cmdlet (alias = "dir) to get the Test.txt file. It saves it in the $a variable.

The second command adds the note property to the object in $a.

The third command uses dot notation to get the value of the Status property of the object in $a. As the output shows, the value is "Done".

C:\PS>$a = dir c:\ps-test\test.txt

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

C:\PS> $a.filelength

Description
-----------
These commands add the FileLength alias property to the object that represents the Test.txt file. The new property is an alias for the Length property. 

The first command use the Get-ChildItem cmdlet (alias = "dir") to get the Test.txt file.

The second command adds the FileLength alias property.

The third command uses dot notation to get 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

Description
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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 $a -membertype ScriptMethod -name PadBoth -value {$p = $this.padleft($this.length + 1); $p.padright($p.length + 1)} -passthru

C:\PS> $a.Padboth()

 This is a string.

Description
-----------
These commands add the PadBoth script method to a string object. 

The first command creates a string and saves it in the $a variable.

The second command adds the Padboth script method to the object in the $a variable. The Value parameter defines the new script method. It uses the PadRight and PadLeft methods of a string to add one space the left and one space to the right of the string. 

The Value parameter also uses the $this automatic variable, which represents the current object. The $this variable is valid only in script blocks that define new properties and methods.

The command includes the Passthru parameter which directs Add-Member to return an instance of the object that includes the new script property. By default, Add-Member does not generate any output.

The third command uses dot notation to call the new Words script method on the object in the $a variable.

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

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

   TypeName: System.DateTime

Name				 MemberType	 Definition
----				 ----------	 ----------
Add				Method		 System.DateTime Add(System.TimeSpan value)
AddDays			Method		 System.DateTime AddDays(double value)
AddHours			 Method		 System.DateTime AddHours(double value)
AddMilliseconds	Method		 System.DateTime AddMilliseconds(double value)
AddMinutes		 Method		 System.DateTime AddMinutes(double value)
...

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

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

   TypeName: System.String

Name			 MemberType			Definition
----			 ----------			----------
Clone			Method				System.Object Clone()
CompareTo		Method				int CompareTo(System.Object value), int CompareTo(string strB)
Contains		 Method				bool Contains(string value)

Description
-----------
These commands add the "When" alias property to an event in the System event log. The event is an EventLogEntry object that is returned by the Get-EventLog cmdlet. 

The "When" alias property 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 get the newest event in the System event log. It stores the event in the $event variable. 

The second command uses dot notation to get the TimeWritten property of that event and pipes it to the Get-Member cmdlet to demonstrate that the property is a DateTime type. 

The third command uses the Add-Member cmdlet to add the When alias property to the object instance in the $event variable. The Name parameter assigns the name, "When," and the Value parameter specifies that When is an alias for the TimeWritten property. The SecondValue parameter indicates that the value that the When method returns should be cast to a System.String type. 

The fourth command uses dot notation to call the new When method. The command pipes the method value to the Get-Member cmdlet to confirm that it has returned a 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)
   }
}

Description
-----------
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.