I am building a C# (WCF) application and it uses a dll Since I am working with CUDA programming., I have written a small program in CUDA C++ which returns a string and generated Dll of it. String Contains Information about Nvidia GPU card (mostly one page Information) .
.I am using PInvoke - (Dllexport and DllImport). C# application is importing this Dll . After running the application I am getting the following exception
-> System.AccessViolationException : Attempting to read or write the protected memory .
As I searched through internet ,many opinions suggests, it is problem of marshalling the data from unmanaged code to managed code.
Is there effective way to return a string from Dll to c# application. I have struck with this from many days. Any possible help is highly appreciable.! Thank You!!!
You should allocate string (StringBuilder) in C# application and pass it to C++ function with specified length.
In C++:
void GetInfo(char* str, int len);
...
In C#:
[DllImport("...", CallingConvention = CallingConvention.Cdecl)
static extern void GetInfo(StringBuilder str, int len);
....
StringBuilder sb = new StringBuilder(10);
GetInfo(sb, sb.Capacity);
Based on your problem description, it is entirely possible that the issue has nothing to do with CUDA, and relates to a more basic programming error related to interfacing managed and unmanaged code.
Having said that, you should also be aware of the fact (at least it was a fact the last time I wrote CUDA code not too long ago; I am boldly assuming that things have not changed and I am not making a fool of myself here) that CUDA code on Windows requires desktop access in order to be able to access the GPU. In other words, any CUDA code must run in the context of the interactive desktop session. Depending on how your WCF service application is implemented, this could be a problem (e.g., if it is actually running as a Windows service, the CUDA code will not work.)
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