Software development blog

I´ve been looking for a way to verify, from within Visual C#, whether a required COM component dynamic link library (DLL) has  indeed been registered in the system and that our dependent class can you use without fear.

In the way to the solution I found approaches using kernel32 LoadLibrary and FreeLibrary calls which actually only verify the existence of the component but nothing about whether it has been registered in the Windows registry.

The most reliable way to do this verification is to use a static method named GetTypeFromProgID,  available in the TYPE class, from the CLR,

This method attempts to load a particular type from the DLL under test.
If successfull it should return the full qualified type. Otherwise, if the DLL is not registered, it will render a NULL result.

This method takes a string parameter which is the ProgID. If progID is a valid entry in the registry and a type is associated with it; otherwise, Nothing

The sample code:

using System;
using System.Runtime.InteropServices;
namespace ComDllVerification
{
    class Program
    {
        static void Main(string[] args)        
        {
            try
            {
                Type T = Type.GetTypeFromProgID("WIA.DeviceManager");
                
                if (T != null)
                {
                    // Safe to go...
                }
            }
            catch (COMException ex)
            {
                // Handle the COM exception here...
            }
        }
    }
}