So Powershell comes with a lot of commands\/CmdLets but as a developer I’m always interested in how I might write my own. Whilst it’s likely that combining existing commands might produce the results you’re after, if it doesn’t we can resort to writing our own command using C#.<\/p>\n
Hello World CmdLet<\/strong><\/p>\n Now we’ve got everything set-up we need to make our CmdLet do something. Here’s the source for a good old HelloWorld Cmdlet<\/p>\n The CmdLetAttribute takes a string for the verb, in this case I’m reusing the VerbsCommon.Get string. The next requirements is the noun, the name of the Cmdlet. So in this case the two go together to give us the Cmdlet Get-HelloWorld.<\/p>\n We derive our class from Cmdlet<\/em> as we’re not dependent upon the Powershell runtime, if we were we’d derive from the PSCmdlet<\/em>.<\/p>\n Importing and using the new CmdLet<\/strong><\/p>\n Once we’ve built our CmdLet and assuming it’s been built with the same version of .NET as supported by the installed Powershell, we can import the “module” into Powershell using<\/p>\n Obviously replacing the path and DLL with the location and DLL you’re installing<\/em><\/p>\n Once imported we can simply run<\/p>\n Autocomplete also works if you type Get-He<\/em> then press tab and you’ll find Get-HelloWorld presented.<\/p>\n If you need to rebuild your Cmdlet you’ll need to close the Powershell instance to remove the instance from it, I tried Remove-Module MyCmdLets<\/em> but this only removes its availability to Powershell, i.e. you can no longer run it, but I guess, like in C# applications, once the module is in the AppDomain you cannot fully unload it.<\/p>\n Parameters<\/strong><\/p>\n Let’s add a parameter to the Cmdlet. <\/p>\n So now, we’ve added a mandatory parameter Name<\/em>. When we run the Get-HelloWorld Cmdlet we can now supply the name, thus<\/p>\n Returning objects<\/strong><\/p>\n So far we’ve returned a string, but what about if we want to return and object or better still multiple objects, like Get-Process might.<\/p>\n Now running this from Powershell will list two columns, Name and Description and three rows with the name and description as per our objects.<\/p>\n Better still we can now write commands such as<\/p>\n\n
\r\n[Cmdlet(VerbsCommon.Get, "HelloWorld")]\r\npublic class GetHelloWorld : Cmdlet\r\n{\r\n protected override void ProcessRecord()\r\n {\r\n WriteObject("Hello World");\r\n }\r\n}\r\n<\/pre>\n\r\nImport-Module c:\\Dev\\MyCmdLets.dll\r\n<\/pre>\n
\r\nGet-HelloWorld\r\n<\/pre>\n
\r\n[Cmdlet(VerbsCommon.Get, "HelloWorld")]\r\npublic class GetHelloWorld : Cmdlet\r\n{\r\n [Parameter(Mandatory = true)]\r\n public string Name { get; set; }\r\n\r\n protected override void ProcessRecord()\r\n {\r\n WriteObject("Hello World " + Name);\r\n }\r\n}\r\n<\/pre>\n\r\nGet-HelloWorld -Name Scooby\r\n<\/pre>\n
\r\n[Cmdlet(VerbsCommon.Get, "HelloWorld")]\r\npublic class GetHelloWorld : Cmdlet\r\n{\r\n protected override void ProcessRecord()\r\n {\r\n WriteObject(new HelloObject { Name = "Scooby", Description = "Dog"} );\r\n WriteObject(new HelloObject { Name = "Shaggy", Description = "Man" });\r\n WriteObject(new HelloObject { Name = "Daphne", Description = "Woman" });\r\n }\r\n}\r\n\r\npublic class HelloObject\r\n{\r\n public string Name { get; set; }\r\n public string Description { get; set; }\r\n}\r\n<\/pre>\n\r\nGet-HelloWorld | where {$_.Description -eq "Dog"}\r\n<\/pre>\n