How do you use a "C" dll from within a C# app?

[TBlob]

Does anyone know how I can use a dll written in "C" from within a C# application? I have gotten as far as building a C# app and then importing the dll. However, when I call the function, I get an error saying that the dll cannot be loaded.:

// sample code follows

[DllImport("MyDll.dll")]
public static extern int DllFunction();
:
:

public static int Main()
{
DllFunction(); // I get a message that the dll cannot be loaded
}

Thanks for any help (and sample code)!!
-Tom