Net call unmanaged dll in c#

Here you see the steps for using a simple C+ dll in C in. Net Framework 4.1. Open Visual C+ Win 32 Project2. In Application Setting Chose Dll _declspec(dllexport) int subtract(int a,int b) return a-b;  7. Now export *.res file in Resource Folder For Version information8. Now Solution Explorer will looks like 9. After Compile you will see the Debug Folder as10. Now Our Unmanaged Dll is Ready. We build a Managed C App11. Design is like12. Code is as follows[ Dll Import( Our Dll.dll, Calling Convention = Calling Convention. Cdecl)]public static extern int subtract(int a, int b   private void button2_ Click(object sender, Event Args e) int x = Convert. To Int32(text Box1. Text int y = Convert. To Int32(text Box2. Text int z = subtract(x, y Message Box. Show( Required Answer is + Convert. To String(z Answer, Message Box Buttons. OK, Message Box Icon. Information. Out put will be14. In case of Previous Version of.net Code will be (3.5) [ Dll Import( Our Dll.dll )]  public static extern int subtract(int a, int b   private void button2_ Click(object sender, Event Args e) int x = Convert. To Int32(text Box1. Text int y = Convert. To Int32(text Box2. Text int z = subtract(x, y Message Box. Show( Required Answer is + Convert. To String(z Answer, Message Box Buttons. OK, Message Box Icon. Information. Out put will be same for both Few Words:extern C -> which help to show all code within brackets from  outside _declspec(dllexport) int add(int a,int b)-> a.
You need to pinvoke the functions residing in your C+ DLL (exported using extern C ) from your. NET code using the Dll Import Attribute. You can't reference your C+ DLL like a. NET assembly, and you can't use classes from the DLL, only Dll Imported C-like functions. Example from msdn: using System; using System. Runtime. Interop Services; class Example / Use Dll Import to import the Win32 Message Box function. [ Dll Import( user32.dll, Char Set = Char Set. Unicode)] public static extern int Message Box( Int Ptr h Wnd, String text, String caption, uint type static void Main / Call the Message Box function using platform invoke. Message Box(new Int Ptr(0 Hello World!, Hello Dialog, 0.