PowerShell Parameter Sets: Require either A or B to be set

Question

Is there a simple way to have a parameter set that allows either A or B but not both to be specified?

E.G. My script will either accept:

.\SimpleScript.ps1 -A "str1" -X 1 -Y 2 -Z 3

or

.\SimpleScript.ps1 -B "str2" -X 1 -Y 2 -Z 3

but not:

.\SimpleScript.ps1 -A "str1" -B "str2" -X 1 -Y 2 -Z 3

Answer 1

You can write a CmdLet and use Parameter sets.

Have a look to the base documentation at About Functions Advanced Parameters

Param
(
    [parameter(Mandatory=$true,
    ParameterSetName="WithA")]
    [String]
    $A,

    [parameter(Mandatory=$true,
    ParameterSetName="WithB")]
    [String]
    $B,

    [parameter(Mandatory=$true)]
    [Int]
    $X
...
)

Answer 2

You want to use Parameter Sets. By making -A a mandatory parameter in one parameter set and -B mandatory in a different parameter set, supplying both -A and -B will cause PowerShell to be unable to resolve which parameter set you intended, and reject the command (with an error indicating that it couldn't resolve the parameter set). Look at this Scripting Guy column for an example.