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powershellstatic-methods

In Powershell, how does `[Math].GetMethods()` differ from methods in form of [Math]::<method_name>?

I've recently learned a new method [Math].GetMethods() that returns all the methods the class has. That is perplexing me because I have thought all the static methods of a class in PowerShell must be invoked in form of [Math]::<method_name> using the Static member operator ::. And there is no method such as [Math]::GetMethods().

Would you help clear up this confusion? What's the difference between [Math].<method_name> and [Math]::<method_name>? Thank you.

Solution

  • The GetMethods() comes from Sysem.Type, so you are not calling Math's member at all.

    When you use [math] type accelerator, it will return a RuntimeType object. Like so,

    [math].gettype()
IsPublic IsSerial Name                     BaseType
-------- -------- ----                     --------
False    True     RuntimeType              System.Reflection.TypeInfo

    Now, if one calls Math class static method via member access operator . like so,

    [math].abs(-42)

Method invocation failed because [System.RuntimeType] does not contain a method named 'abs'.
At line:1 char:1
+ [math].abs(-42)
+ ~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : MethodNotFound

    There is an error message. Note that it's System.RuntimeType that complains for non-existing method abs.

    To call Math's static members, one needs to use static member operator ::.

    [math]::abs(-42)
42