{"id":16221,"date":"2010-12-14T00:01:00","date_gmt":"2010-12-14T00:01:00","guid":{"rendered":"https:\/\/blogs.technet.microsoft.com\/heyscriptingguy\/2010\/12\/14\/dynamic-method-invocation-in-powershell\/"},"modified":"2010-12-14T00:01:00","modified_gmt":"2010-12-14T00:01:00","slug":"dynamic-method-invocation-in-powershell","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/scripting\/dynamic-method-invocation-in-powershell\/","title":{"rendered":"Dynamic Method Invocation in PowerShell"},"content":{"rendered":"

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Summary:<\/span><\/b> Learn how to create a Windows PowerShell function to implement dynamic method invocation.<\/span><\/p>\n

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\"Hey,<\/span><\/span><\/span><\/span><\/span><\/span><\/span>Hey, Scripting Guy! What can you tell me about dynamic method invocation?<\/span><\/p>\n

— PG<\/span><\/p>\n

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\"Hey,<\/span><\/span><\/span><\/span><\/span><\/span><\/span>Hello PG, Microsoft Scripting Guy Ed Wilson here. Today is day 2 of guest blogger week; we have Trevor Sullivan to tell us about dynamic method invocation.<\/span><\/p>\n

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Trevor Sullivan is a seasoned IT professional, experienced in large-scale systems management, with about 5 years of scripting experience. He picked up PowerShell in late 2007, and has been a fan ever since. At any point in time, Trevor can be found researching new technologies, writing code, or cooking up a new blog post at http:\/\/trevorsullivan.net<\/span><\/a>. He is also very active in public social networks, such as Twitter (@pcgeek86) and various discussion forums and mailing lists. Here’s Trevor!<\/span><\/p>\n

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Background<\/h2>\n

There are situations where invoking a method on an object dynamically is desirable. Wait just a minute. What is dynamic method invocation, and why am I wasting my time reading this? Well, basically it means that you have an object, any ol’ object, and you want to invoke a method on it but you do not know what the method name is. In fact, you do not even know what the object is! It is a concept that is also known as late-binding.<\/span><\/p>\n

Don Jones, a PowerShell MVP and trainer, recently posed some feedback on Microsoft Connect, suggesting that having an Invoke-Method<\/b> cmdlet would be helpful in future versions of PowerShell. Microsoft has already included an Invoke-WmiMethod<\/b> cmdlet but this does not work for arbitrary .NET objects.<\/span><\/p>\n

In Don’s example on Connect, he uses the illustration that currently, in order to call a method on an array of objects, you must iterate over them using a foreach<\/b> loop. He explains that this confuses new students to PowerShell, and could be resolved using a cmdlet that takes an array of objects as its input, and dynamically invokes a method on them.<\/span><\/p>\n

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Solution<\/h2>\n

I took this opportunity to develop a script cmdlet that more or less implements the previously mentioned functionality. A little-known feature of PowerShell is that you can invoke methods without hard-coding the method name. This also applies to an object’s properties. In fact, I realized after I had written this blog post that Jeffrey Snover wrote about this topic a few years back.<\/span><\/p>\n

The script cmdlet I wrote lets you input a few things:<\/span><\/p>\n