Using Static Classes and Methods

Not all .NET Framework classes can be created by using New-Object. For example, if you try to create a System.Environment or a System.Math object with New-Object, you will get the following error messages:

PS> New-Object System.Environment
New-Object : Constructor not found. Cannot find an appropriate constructor for
type System.Environment.
At line:1 char:11
+ New-Object  <<<< System.Environment
PS> New-Object System.Math
New-Object : Constructor not found. Cannot find an appropriate constructor for
type System.Math.
At line:1 char:11
+ New-Object  <<<< System.Math

These errors occur because there is no way to create a new object from these classes. These classes are reference libraries of methods and properties that do not change state. You don't need to create them, you simply use them. Classes and methods such as these are called static classes because they are not created, destroyed, or changed. To make this clear we will provide examples that use static classes.

Getting Environment Data with System.Environment

Usually, the first step in working with an object in Windows PowerShell is to use Get-Member to find out what members it contains. With static classes, the process is a little different because the actual class is not an object.

Referring to the Static System.Environment Class

You can refer to a static class by surrounding the class name with square brackets. For example, you can refer to System.Environment by typing the name within brackets. Doing so displays some generic type information:

PS> [System.Environment]

IsPublic IsSerial Name									 BaseType
-------- -------- ----									 --------
True	 False	Environment							System.Object
Note:

As we mentioned previously, Windows PowerShell automatically prepends 'System.' to type names when you use New-Object. The same thing happens when using a bracketed type name, so you can specify [System.Environment] as [Environment].

The System.Environment class contains general information about the working environment for the current process, which is powershell.exe when working within Windows PowerShell.

If you try to view details of this class by typing [System.Environment] | Get-Member, the object type is reported as being System.RuntimeType , not System.Environment:

PS> [System.Environment] | Get-Member

   TypeName: System.RuntimeType

To view static members with Get-Member, specify the Static parameter:

PS> [System.Environment] | Get-Member -Static


   TypeName: System.Environment

Name					 MemberType Definition
----					 ---------- ----------
Equals					 Method	 static System.Boolean Equals(Object ob...
Exit					 Method	 static System.Void Exit(Int32 exitCode)
...
CommandLine				Property   static System.String CommandLine {get;}
CurrentDirectory		 Property   static System.String CurrentDirectory ...
ExitCode				 Property   static System.Int32 ExitCode {get;set;}
HasShutdownStarted		 Property   static System.Boolean HasShutdownStart...
MachineName				Property   static System.String MachineName {get;}
NewLine					Property   static System.String NewLine {get;}
OSVersion				Property   static System.OperatingSystem OSVersio...
ProcessorCount			 Property   static System.Int32 ProcessorCount {get;}
StackTrace				 Property   static System.String StackTrace {get;}
SystemDirectory			Property   static System.String SystemDirectory {...
TickCount				Property   static System.Int32 TickCount {get;}
UserDomainName			 Property   static System.String UserDomainName {g...
UserInteractive			Property   static System.Boolean UserInteractive ...
UserName				 Property   static System.String UserName {get;}
Version					Property   static System.Version Version {get;}
WorkingSet				 Property   static System.Int64 WorkingSet {get;}
TickCount							 ExitCode

We can now select properties to view from System.Environment.

Displaying Static Properties of System.Environment

The properties of System.Environment are also static, and must be specified in a different way than normal properties. We use :: to indicate to Windows PowerShell that we want to work with a static method or property. To see the command that was used to launch Windows PowerShell, we check the CommandLine property by typing:

PS> [System.Environment]::Commandline
"C:\Program Files\Windows PowerShell\v1.0\powershell.exe"

To check the operating system version, display the OSVersion property by typing:

PS> [System.Environment]::OSVersion

		 Platform ServicePack		 Version			 VersionString
		 -------- -----------		 -------			 -------------
			Win32NT Service Pack 2	5.1.2600.131072	 Microsoft Window...

We can check whether the computer is in the process of shutting down by displaying the HasShutdownStarted property:

PS> [System.Environment]::HasShutdownStarted
False  

Doing Math with System.Math

The System.Math static class is useful for performing some mathematical operations. The important members of System.Math are mostly methods, which we can display by using Get-Member.

Note:

System.Math has several methods with the same name, but they are distinguished by the type of their parameters.

Type the following command to list the methods of the System.Math class.

PS> [System.Math] | Get-Member -Static -MemberType Methods


   TypeName: System.Math

Name			MemberType Definition
----			---------- ----------
Abs			 Method	 static System.Single Abs(Single value), static Sy...
Acos			Method	 static System.Double Acos(Double d)
Asin			Method	 static System.Double Asin(Double d)
Atan			Method	 static System.Double Atan(Double d)
Atan2		 Method	 static System.Double Atan2(Double y, Double x)
BigMul		Method	 static System.Int64 BigMul(Int32 a, Int32 b)
Ceiling		 Method	 static System.Double Ceiling(Double a), static Sy...
Cos			 Method	 static System.Double Cos(Double d)
Cosh			Method	 static System.Double Cosh(Double value)
DivRem		Method	 static System.Int32 DivRem(Int32 a, Int32 b, Int3...
Equals		Method	 static System.Boolean Equals(Object objA, Object ...
Exp			 Method	 static System.Double Exp(Double d)
Floor		 Method	 static System.Double Floor(Double d), static Syst...
IEEERemainder   Method	 static System.Double IEEERemainder(Double x, Doub...
Log			 Method	 static System.Double Log(Double d), static System...
Log10		 Method	 static System.Double Log10(Double d)
Max			 Method	 static System.SByte Max(SByte val1, SByte val2), ...
Min			 Method	 static System.SByte Min(SByte val1, SByte val2), ...
Pow			 Method	 static System.Double Pow(Double x, Double y)
ReferenceEquals Method	 static System.Boolean ReferenceEquals(Object objA...
Round		 Method	 static System.Double Round(Double a), static Syst...
Sign			Method	 static System.Int32 Sign(SByte value), static Sys...
Sin			 Method	 static System.Double Sin(Double a)
Sinh			Method	 static System.Double Sinh(Double value)
Sqrt			Method	 static System.Double Sqrt(Double d)
Tan			 Method	 static System.Double Tan(Double a)
Tanh			Method	 static System.Double Tanh(Double value)
Truncate		Method	 static System.Decimal Truncate(Decimal d), static...

This displays several mathematical methods. Here is a list of commands that demonstrate how some of the common methods work:

PS> [System.Math]::Sqrt(9)
3
PS> [System.Math]::Pow(2,3)
8
PS> [System.Math]::Floor(3.3)
3
PS> [System.Math]::Floor(-3.3)
-4
PS> [System.Math]::Ceiling(3.3)
4
PS> [System.Math]::Ceiling(-3.3)
-3
PS> [System.Math]::Max(2,7)
7
PS> [System.Math]::Min(2,7)
2
PS> [System.Math]::Truncate(9.3)
9
PS> [System.Math]::Truncate(-9.3)
-9