Forcing the VB6 compiler to use early binding when calling a .net com dll

Question

I have a com dll written in c# After running Regasm I can call this dll from VB6, referencing the com dll. In VB6 I have intellisense available.

However when I press F5 to compile the compiler does not catch any mistakes in calling the com dll. It must be using late binding.

How can I get it to use early binding?

The interface is declared

using System.Runtime.InteropServices;   
namespace combridge    
{
[Guid("2f4b6041-91e3-4d9f-a9f5-9bd4adfd1789")]  
[ComVisible(true)]  
[InterfaceType(ComInterfaceType.InterfaceIsDual)]
    public interface IBridge    
     {
      // methods go here
     }    
  }

The main class is declared

[Guid("085777fa-9397-4cfd-843a-85ececb86789")]
[ProgId("companyname.ComBridge")]
[ClassInterface(ClassInterfaceType.None)]
[ComVisible(true)]
public class BridgeImplementation : IBridge
{
    #region Public Implementation

    [DispId(1)]
    [ComVisible(true)]
    public string EchoTest(string message)
    {
        return string.Format("Echo '{0}' at {1:T}", message, DateTime.Now);
    }

 // etc

[update]

In the VB6 project I reference the tlb file which I create using

c:\WINDOWS\Microsoft.Net\Framework\v4.0.30319/regasm /verbose /codebase /tlb:CommBridge.tlb ComBridge.dll

In the VB6 I create the object using

Dim o As BridgeImplementation
Set o = New BridgeImplementation
o.EchoTest  // executes
o.NonExistantFunction // run time error

You are missing nonextensible attribute on the IBridge interface for some reason. VB6 client is not using late-bound on recognized methods for sure. Missing nonextensible allows clients to call methods with custom names through IDispatch interface. These method names are not known at compile time. (e.g. ADO.Connection can execute stored procedures as methods on the conn object). Check IDL source dump from OLE View or post it here. — wqw

Kirsten Greed Kirsten Greed · Accepted Answer · 2014-08-24T23:00:55

Above the interface declaration I replaced

[InterfaceType(ComInterfaceType.InterfaceIsDual)]

with

[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]

and it solved the problem

Forcing the VB6 compiler to use early binding when calling a .net com dll

1 Answers