Determine the number of parameters of a function

[DanielGerlach2]

I have a use case where I have instruction code that has "optional" parameters.

When executing the code so far, I had a way to determine how many parameters a function had, and accordingly, it was then called with exactly that number of parameters (or an empty string if necessary).

Select Case pFunction.ArgsCount
  Case 0
    ScriptEngine.Invoke(FunctionName)
  Case 1
    ScriptEngine.Invoke("Main", Param(0))
  Case 2
    ScriptEngine.Invoke("Main", Param(0), Param(1))
...

Unfortunately, I haven't yet found a way to determine the number of parameters in ClearScript.

Here is some sample code where I get the following error "Invalid object or property access":

Imports Microsoft.ClearScript.Windows

Public Module App
    Sub Output(Text As String)
        Console.WriteLine(Text)
    End Sub

    Sub Wait()
        Console.ReadKey()
    End Sub
End Module

Module Module1
    Sub Main()
        Dim dtNow As Date
        dtNow = Now

        Dim strCode As String = "
Sub Main(DateFrom, DateTo)

        Dim s

        If IsEmpty(DateFrom) Then
            DateFrom = now
        End If

        If IsEmpty(DateTo) Then
            DateTo = DateAdd(""d"", 7, now)
        End If

        s = ""DummyText '{@ReferenceDateFrom}', '{@ReferenceDateTo}'""

        s = replace( s, ""{@ReferenceDateFrom}"", DateFrom )
        s = replace( s, ""{@ReferenceDateTo}"", DateTo )

        App.Output(s)

        App.Wait

End Sub"


        Using ScriptEngine As New Microsoft.ClearScript.Windows.VBScriptEngine(WindowsScriptEngineFlags.EnableDebugging Or WindowsScriptEngineFlags.MarshalDateTimeAsDate)
            ScriptEngine.AddHostType(GetType(App))
            ScriptEngine.Execute(String.Join(vbCrLf, strCode))
            If ProcedureExists(ScriptEngine, "Main") Then
                ScriptEngine.Invoke("Main", dtNow)
                'ScriptEngine.Invoke("Main", dtNow, dtNow.AddDays(1))
            End If

        End Using
    End Sub

    Private Function ProcedureExists(ScriptEngine As Microsoft.ClearScript.Windows.VBScriptEngine, Name As String) As Boolean

        Return DirectCast(ScriptEngine.Script, Microsoft.ClearScript.ScriptObject).PropertyNames.Where(Function(x) Not x.ToLower.StartsWith("engineinternal")).ToList.Contains("Main", StringComparer.OrdinalIgnoreCase)

    End Function

End Module

How can I determine the number of parameters of a function?

[ClearScriptLib]

Hi @DanielGerlach2,

Unfortunately, we aren't aware of a simple and reliable way to retrieve the parameter count of a VBScript function.

In theory, since VBScript objects implement IDispatch, it might be possible to invoke GetTypeInfo and get the parameter count via the returned ITypeInfo. However, our understanding is that VBScript functions don't expose parameter information that way.

Your best option might therefore be to track expected argument counts manually.

Good luck!