[ClassName]::MethodName(parameter list)

Some methods relate only to the concept the class represents. For example, retrieving all running processes on a system relates to the general concept of processes. Methods that apply to the class/type as a whole are called static methods.

For example:

PS >[System.Diagnostics.Process]::GetProcessById(0)

gets the process with the ID of 0 and displays the following output:

Handles  NPM(K)    PM(K)      WS(K)  VM(M)   CPU(s)     Id ProcessName
-------  ------    -----      -----  -----   ------     -- -----------
    0     0      0     16               0 0 Idle

$objectReference.MethodName(parameter list)

Some methods relate only to specific, tangible realizations (called instances) of a class. An example of this would be a process actually running on the system, as opposed to the general concept of processes. If $objectReference refers to a specific System.Diagnostics.Process (as output by GetProcessById(), for example,), you may want to start it, stop it, or wait for it to exit. Methods that act on instances of a class are called instance methods.

The term object is often used interchangeably with the term instance.

For example:

PS >$process = [System.Diagnostics.Process]::GetProcessById(0)
PS >$process.Refresh()

Stores the process with ID of 0 into the $process variable. It then calls the Refresh() instance method on that specific process.

PS >$now = [DateTime]::Now
PS >$now.AddDays

MemberType          : Method
OverloadDefinitions : {System.DateTime AddDays(Double value)}
TypeNameOfValue     : System.Management.Automation.PSMethod
Value               : System.DateTime AddDays(Double value)
Name                : AddDays
IsInstance          : True

$objectReference.PropertyName

or:

$objectReference.PropertyName = <value>

Like static methods, some properties relate only to information about the concept that the class represents. For example, the System.DateTime class “represents an instant in time, typically expressed as a date and time of day.” It provides a Now static property that returns the current time:

PS >[System.DateTime]::Now
Sunday, July 16, 2006 2:07:20 PM

Although relatively rare, some types allow you to set the value of some static properties.

$objectReference.PropertyName

$objectReference.PropertyName = <value>

PS >$today = [System.DateTime]::Now
PS >$today.DayOfWeek
Sunday

The two primary avenues for learning about classes and types are the Get-Member cmdlet and the documentation for the .NET Framework.

To learn what methods and properties a given type supports, pass it through the Get-Member cmdlet.

<classname> members

When you specify a type name, PowerShell allows you to use a short form for some of the most common types.

$objectReference = New-Object TypeName [parameter list]

Although static methods and properties of a class generate objects, you will often want to create them explicitly yourself. PowerShell’s New-Object cmdlet lets you create an instance of the type you specify. The parameter list must match the list of parameters accepted by one of the type’s constructors, as documented on MSDN.

For example:

$webClient = New-Object Net.WebClient
$webClient.DownloadString("http://search.msn.com")

Most common types are available by default. However, many are available only once you load the library (called the assembly) that defines them. The MSDN documentation for a class includes the assembly that defines it.

To load an assembly, use the methods provided by the System.Reflection.Assembly class:

PS >[Reflection.Assembly]::LoadWithPartialName("System.Web")

GAC   Version        Location
---   -------        --------
True  v2.0.50727     C:WINDOWSassemblyGAC_32(…)System.Web.dll


PS >[Web.HttpUtility]::UrlEncode("http://search.msn.com")
http%3a%2f%2fsearch.msn.com

PowerShell allows you to access methods and properties on COM objects the same way you would interact with objects from the .NET Framework. To interact with a COM object, use its ProgId with the –ComObject parameter (often shortened to –Com) on New-Object:

PS >$shell = new-object -Com Shell.Application

PS >$shell.Windows() | select LocationName,LocationUrl

PowerShell supports two ways to add your own methods and properties to any type: the Add-Member cmdlet, and a custom types extension file.

$testObject = [PsObject] "Test"
$testObject | Add-Member "AliasProperty" Count
Length
$testObject.Count

System.Reflection.MethodInfo.

$testObject = [PsObject] "Test"
$testObject | Add-Member NoteProperty Reversed tseT
$testObject.Reversed

$testObject = [PsObject] ("Hi" * 100)
$testObject | Add-Member ScriptProperty IsLong {
     $this.Length -gt 100
   }
$testObject.IsLong

$testObject = [PsObject] [DateTime]::Now
$collection = new-object `
Collections.ObjectModel.Collection``1[System.String]
$collection.Add("Month")
$collection.Add("Year")
$testObject | Add-Member PropertySet MonthYear
$collection
$testObject | select MonthYear

System.Reflection.MethodInfo.

$testObject = [PsObject] "Hello"
$testObject | Add-Member ScriptMethod IsLong {
     $this.Length -gt $args[0]
   }
$testObject.IsLong(3)
$testObject.IsLong(100)