Powershell C# cmdlet with parametersets with same subset of parameters

Question

I have defined the following parameter sets in MyCustomCmdlet with default parameterset as two:

    [Parameter(Mandatory = true, ParameterSetName = one)]
    [Parameter(Mandatory = true, ParameterSetName = two)]
    [Parameter(Mandatory = true, ParameterSetName = three)]
    [Parameter(Mandatory = true, ParameterSetName = four)]
    [ValidateNotNullOrEmpty]
    [Alias("a")]
    public string A { get; set; }

    [Parameter(Mandatory = true, ParameterSetName = two)]
    [ValidateNotNullOrEmpty]
    [Alias("b")]
    public string B { get; set; }

    [Parameter(Mandatory = true, ParameterSetName = three)]
    [SupportsWildcards]
    [ValidateNotNullOrEmpty]
    [Alias("c")]
    public string C { get; set; }


    [Parameter(Mandatory = true, ParameterSetName = four)]
    [ValidateNotNullOrEmpty]
    [Alias("d")]
    public string D { get; set; }


    [Parameter]
    [ValidateNotNullOrEmpty]       
    public string E{ get; set; }

    [Parameter]
    [ValidateNotNullOrEmpty]
    public string F { get; set; }

During debug, am getting expected number of parameter sets i.e. 4 with following parameters:

1.ParameterSetName: one Parameters: A , E, F

2.ParameterSetName: two Parameters: A, B , E, F

3.ParameterSetName: three Parameters: A, C , E, F

4.ParameterSetName: four Parameters: A, D , E, F

However, when I execute:

MyCustomCmdlet -A or MyCustomCmdlet -A -E -F

I am getting error stating, requires mandatory parameter B which is part of default parameter set.

Can someone please help me understand this behavior?
How to execute the cmdlet using parameter set "one"

The Fish · Accepted Answer · 2018-09-20 12:27:42Z

1

PowerShell will try and resolve the ParameterSet based off the command given and will not try and resolve a non default ParameterSet unless there the default is not resolvable with the current inputs. In your scenario ParameterSet 'two' is default and Parameter A is part of that ParameterSet, so logically that's what PowerShell assumes you're targeting as the input is still valid for it. If you want the ability to provide Parameter A on it's own you need to create a ParameterSet with just Parameter A included, and this has to be default (ParameterSet 'one' in your example).

E and F do not have their ParameterSet property defined, so by default their ParameterSet is set to ParameterSet.AllParameterSets, so again including these two fields is valid for the default set, so PowerShell still assumes that's what you're trying to do.

Also PowerShell is case-insensitive, so you don't need to Alias your parameters with the lower-case equivalent (if that is a representative scenario)

answered Sep 20, 2018 at 12:27

The Fish

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3 Comments

Scorp Over a year ago

Thanks a lot Fish! It was very helpful. I was just going to drop the parametersets and do the validation in the code.

The Fish Over a year ago

Why not just set the default to 'one'? :) ParameterSets work well with Intellisense

Scorp Over a year ago

Yes, finally did set the default to 'one's.

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