VB.net dll use with C# windows form

BobbyStrain

I have a VB.NET class library with a single public function with a single parameter that calls a method to produce the string return value. I referenced it in the C# project, and added a using statement for the namespace. However, I have no success in even coding to use the function from the dll. Can someone point me in the right direction? There are lots of answers to the problem on the web, but none work for me. Here is a portion of the VB dll code. GetSeparators() prepares and returns the string. I am developing the library to get information from a COM library. I have not found a convenient code for C# to use the COM library. The VB dll is NET 3.5 and the C# app is NET 4.6.1.

Public Class HYSYSFetch

Private \_filename As String
Private \_sepstring As String = ""

Public Function FetchSeparators(filename As String) As String
    \_filename = filename
    GetSeparators()
    Return \_sepstring
End Function

OriginalGriff

All you have to do is create an instance of the containing class, and call the function on that

private void MyFunction()
{
HYSYSFetch hsf = new HYSYSFetch(...); // Fill in the details from your constructor
string result = hsf.FetchSeparators(strPathToFile);
}

If that doesn't work, you need to tell us exactly what you get as an error message, and show us the exact code you tried.

Sent from my Amstrad PC 1640 Never throw anything away, Griff Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!

BobbyStrain

Thank you. This is something I have done a hundred times with projects. But I never used a VB dll with a C# project. I shall remember that the right solution is the simple one.

OriginalGriff

Once they are compiled, VB and C# DLLs are the same thing - you can treat them as if they were written in any language. (The same applies to any language which compiles to IL, so F#, Cobol, C++ - all "look the same" once compiled.)

Sent from my Amstrad PC 1640 Never throw anything away, Griff Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!

BobbyStrain

Griff, Once you cleared the fog and got me started, the rest was easy. Everything works smoothly when the C# application calls the VB.NET library functions. Thanks again. I needed the VB library because C# doesn't easily communicate with a COM object. And I already had the VB code in a VB application. I develop most of my class libraries with C#, just to keep in practice. My VB application that uses Selenium Basic (Selenium wrapper for VB & VBA) doesn't play with Firefox latest editions. So my need to use C# to make use of Selenium which doesn't work with VB. My main use is to get information from a process simulator and transfer it to a web page, thus eliminating transcribing errors. This takes several technologies to get it to work.

OriginalGriff

You're welcome!

Sent from my Amstrad PC 1640 Never throw anything away, Griff Bad command or file name. Bad, bad command! Sit! Stay! Staaaay... AntiTwitter: @DalekDave is now a follower!

BobbyStrain

Well, I spoke too soon. The VB dll is not playing well with the C# app. The C# app doesn't recognize a particular method in the dll. Call to a different method works OK. Throws an error, something about Reflection and the wrong number of arguments. But the number of arguments is correct; there is only one. I had an earlier version working, but the C# app was not getting the proper data from the dll which fetches data from a COM app. I'll have to go back to an earlier version and trace the problem.

Mycroft Holmes

Don't forget the error may have "bubbled up" from a method below the one you are calling.

Never underestimate the power of human stupidity RAH

BobbyStrain

Turns out I had a few minor errors in the VB code. I found all of them, and cleaned up the code while I was finding them. It all works as it should. I learned a lot with this little project. It was a cascade with a C# app calling a VB.NET dll which in turn called a licensed COM library. So there was lots of opportunity to get the code wrong. Thanks for the help.