How to discover PowerShell Script parameters in c#

Question

We want to store and manage PowerShell scripts in a database an execute them via C#. How can we discover the parameters of such a script before executing it? so we can set them to known values or prompt a user for values.

Some clarification:

We create a management system MS.

An admin stores a PowerShell script in the MS database.
Later a different admin selects this script from a list offered by the MS.
MS discovers the parameters of the script.
MS prompts the admin for values.

MS executes the script with the parameters supplied.

    string testScript = @"
        {
            param(
                [ValidateNotNullOrEmpty()]
                [string]$Name
            )
            get-process $name
        ";

Dictionary<string,object> DiscoverParameters()
{
    using (PowerShell psi = PowerShell.Create())
    {
        psi.AddScript(testScript);
        var pars = new Dictionary<string,object>();
        //How do we get at the parameters
        return pars;
    }
}

void ExecuteScript(Dictionary<string,object> pars)
{
    using (PowerShell psi = PowerShell.Create())
    {
        psi.AddScript(testScript);
        pars.ToList().ForEach(p => psi.AddParameter(p.Key, p.Value));
        Collection<PSObject> PSOutput = psi.Invoke();
        //...
    }
}

mjolinor · Accepted Answer · 2014-10-15 20:44:04Z

3

You can use the PS parser, and access the parameter information via AST:

$scriptfile = '<full path to script file>'
$AST = [System.Management.Automation.Language.Parser]::ParseFile( $scriptfile,[ref]$null,[ref]$null)

$AST.ParamBlock.Parameters | ft

answered Oct 15, 2014 at 20:44

mjolinor

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Comments

Mike Zboray · Accepted Answer · 2014-10-17 08:22:26Z

mjolinor is correct that using the PowerShell parser is probably the best way to get the parameters. That example is in PowerShell, below is an example in C#. I'm not quite sure what you are looking for with the parameters being Dictionary<string, object>. Here we just stick the names into the list although there is other info you could pull out like the static type.

using System.Management.Automation;
using System.Management.Automation.Language;

static void Main(string[] args)
{
    const string testScript = @"
    param(
        [ValidateNotNullOrEmpty()]
        [string]$Name
    )
    get-process $name
";
    foreach(var parameter in GetScriptParameters(testScript))
    {
        Console.WriteLine(parameter);
    }
}

private static List<string> GetScriptParameters(string script)
{
    Token[] tokens;
    ParseError[] errors;
    var ast = Parser.ParseInput(script, out tokens, out errors);
    if (errors.Length != 0)
    {
        Console.WriteLine("Errors: {0}", errors.Length);
        foreach (var error in errors)
        {
            Console.WriteLine(error);
        }
        return null;
    }

    return ast.ParamBlock.Parameters.Select(p => p.Name.ToString()).ToList();
}

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