Invoke an overloaded method from a COM Object using reflection?

Question

I am attempting to invoke a method from a product COM API in my application.

I can successfully invoke the method with a single parameter using the code below but I need to pass some extra parameters (which are added as overloads).

Type _apiType = Type.GetTypeFromProgID("TheAPI.TheServer");
object _api = Activator.CreateInstance(_apiType);

_apiType.InvokeMember(
    "Connect",
    System.Reflection.BindingFlags.InvokeMethod,
    null,
    _api,
    new object[] { 2 } // new object[] {2, "", "" }
);

I have tried adding additional parameters into the code I have above but I get the following error:

"Number of parameters specified does not match the expected number."

I can't seem to find any answer to this, I'm starting to think it's not possible. All the examples I have found suggest using Type.GetMethod() but this doesn't seem to work on COM Objects.

Number of parameters specified does not match the expected number So your method "Connect" doesn't expect 1 parameter. — L.B
– L.B, Commented Aug 11, 2014 at 19:05
COM does not support method overloads. Double-check your COM interface to make sure the method name hasn't been changed for the second "overload" (e.g. Connect_3) — D Stanley
– D Stanley, Commented Aug 11, 2014 at 19:06
The method 'Connect' has multiple other overloaded methods: void Connect(); void Connect(TheClientType nType); void Connect(TheClientType nType, string strUser, string strPwd); void Connect(TheClientType nType, string strUser, string strPwd, string strNode, string strAlias, bool bAllowUI); — joshua1307
– joshua1307, Commented Aug 11, 2014 at 19:07
As @DStanley suggested...See here: msdn.microsoft.com/en-us/library/28w1w83f(v=vs.110).aspx ... if you created your COM Server ("TheAPI.TheServer") using .NET and created a C# interface with overloaded methods...the unmanaged/published COM signatures of those methods (i.e. in the typelibrary) are decorated... see the section where it mentions "Unmanaged signature". To confirm this, you could use "View | Object Browser | Edit Custom Component Set | (use COM or Browse to choose your COM component)...then you can see what methods are defined in the coclasses and interfaces. — Colin Smith
– Colin Smith, Commented Aug 11, 2014 at 20:58
@colinsmith and DStanley - Thank you both for your response! Using the Object Browser as colinsmith suggested had shown that the method I was attempting to use was actually called ConnecEx. I have modified my code to use the 'ConnectEx' method and it works like a charm! Thank you! — joshua1307
– joshua1307, Commented Aug 11, 2014 at 22:46

joshua1307 · Accepted Answer · 2014-08-12 07:49:13Z

2

COM does not support method overloads. The unmanaged/published COM signatures of those methods (i.e. TypeLibrary) are decorated - see the section that mentions "Unmanaged Signature" in the MSDN article below. http://msdn.microsoft.com/en-us/library/28w1w83f(v=vs.110).aspx

To find the actual method name do the following in Visual Studio: View | Object Browser | Edit Custom Component Set | (Browse to COM Component)

This will show all of the actual method names.

answered Aug 12, 2014 at 7:49

joshua1307

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