Delphi-Dll function with return Boolean throw AccessViolationException

Question

Hello,

i use a Delphi-Win32-Dll in C# (.Net 4.0, VS 2010).

All functions works fine, but only the function with returns Delphi-Boolean throws AccessviolationException.

here is a litle bit of Code:

Delphi function-Typedef:

DbOpen = function: Boolean; stdcall;

C# function Typedef:

[return: MarshalAs(UnmanagedType.Bool)]
protected delegate Boolean TMatriKSDbOpen();
protected TMatriKSDbOpen matriKSDbOpen;

C#-Dynamic-Dll loading

...LoadLibraryEx...
        public Delegate CreateDynamicDllDelphi(string functionName, Type delegateType)
        {
            IntPtr funcAddr = GetProcAddress(dllHandle, functionName);
            if (funcAddr == IntPtr.Zero)
                throw new EntryPointNotFoundException("Function: " + functionName);
            return Marshal.GetDelegateForFunctionPointer(funcAddr, delegateType);
        }
matriKSDbOpen = (TMatriKSDbOpen)CreateDynamicDllDelphi("DbOpen", typeof(TMatriKSDbOpen));

c# Using:

bool openOk = matriKSDbOpen(); // throw AccessViolationException

i have also test

[return: MarshalAs(UnmanagedType.I1)]

I'm now out of order ;-((

Answer 1

I don't think the problem is the return value. It could cause an unbalanced stack, not an access violation. Are you sure the function does not have parameters?

Answer 2

Yes this function have non parameters!

All other function (with and without params, returns PChar=>String and Integer=>Int32) works fine.

We have make many tests an we give up.

Now we are change the Type from Boolean to PChar(C# String) '0' and '1' this works.