VBScriptEngine - Compare Enum (Return value) with Integer

[DanielGerlach2]

I have code that is executed via vbscriptengine, where a function returns an enum.

Definition:
Function GetFieldType(Field as String) as FieldTypeEnum

Enum:
Public Enum FieldTypeEnum As Integer
ftUnknown = 0
ftString = 10
ftDate = 8
ftCurrency = 5
End Enum

Unfortunately, a comparison between Enum and Integer is not possible.
If App,GetFieldType("Field1") = 0 Then
...
End If
Throws the Error:
Type mismatch\Type mismatch

If I change the definition to "Function GetFieldType(Field as String) as Integer" the comparision is possible, but I don't want to change the function definition or the code to be executed.

Which settings are necessary so that the comparison of an enum with an intger is possible?

[ClearScriptLib]

Hi @DanielGerlach2,

A .NET enum is not an integer, so that kind of comparison isn't possible without explicit conversion or additional setup.

The recommended approach is to expose the enum type to the script engine:

ScriptEngine.AddHostType(GetType(FieldTypeEnum))

You could then perform type-safe enum comparison in script code:

If App.GetFieldType(""Field1"") Is FieldTypeEnum.ftUnknown Then
    ...
End If

I don't want to change the function definition or the code to be executed.

If that's your requirement, then it's probably best not to expose App to the script engine directly. Instead, you could expose an adapter that provides the exact interface required to accommodate your existing script code.

Good luck!

[DanielGerlach2]

Thank you very much for the quick answer.
I have now broken down the behavior into a test project and made it available as a ZIP.

The code previously worked without any problems with the MSScriptcontrol and now the Clearscript should be used.
Since this and similar code is used in many places, the adjustments should actually only be limited to adjustments in the use/initialization of Clearscript.

https://www.file-upload.net/download-15445694/tstClearscript_625.zip.html

[ClearScriptLib]

Thanks for posting your test app!

The code previously worked without any problems with the MSScriptcontrol and now the Clearscript should be used.

ClearScript is not intended to be a direct replacement for MSScriptControl. Automatic conversion of .NET enums to integers would compromise type safety and break method binding – features that are of vital importance in most .NET scenarios.

Our recommendation remains to use an adapter to accommodate your script code. Here's a partial example:

Public Class SessionAdapter
    Private ReadOnly _session As Session.Session
    Public Sub New(session As Session.Session)
        _session = session
    End Sub
    Public Function GetFieldType(field As String) As Integer
        Return CInt(_session.GetFieldType(field))
    End Function
End Class

And then:

pScript.AddObject("ActSession", New SessionAdapter(pSession))

With that setup in place, the script code behaves as expected.

the adjustments should actually only be limited to adjustments in the use/initialization of Clearscript.

That's exactly the case. The adapter pattern requires no changes to the Session class or script code.

Cheers!