C#

#ifdef __cplusplus
extern "C" {
#endif
__declspec(dllexport) LPVOID CreateClass();
__declspec(dllexport) void DestroyClass(LPVOID lpBuf);
#ifdef _cpluscplus
}
#endif

[DllImport("mylib.dll")]
private static extern IntPtr CreateClass();
[DllImport("mylib.dll")]
private static extern void DestroyClass(IntPtr inst);
// Made-up class method used for example:
[DllImport("mylib.dll", CallingConvention=CallingConvention.ThisCall)]
private static extern int Add(IntPtr inst, int a, int b);

IntPtr inst = CreateClass();
int total = Add(inst, 1, 1);
DestroyClass(inst);

/// <summary>
/// This will appear in the intellisense thingamabob.
/// </summary>

"You can have everything in life you want if you will just help enough other people get what they want." --Zig Ziglar

/// <summary>This class does X.</summary>
/// <remarks>A better, longer description...</remarks>
public class MyClass
{
  /// <summary>
  /// Creates a new instance of the <see cref="MyClass"/> class.
  /// </summary>
  public MyClass()
  {
  }
  /// <summary>Returns <paramref name="param1"/> + 1.</summary>
  /// <param name="param1">Description of param1</param>
  /// <returns>An <see cref="Int32"/> that represents something.
  public int SomeMethod(int param1)
  {
    return param1 + 1;
  }
}

SqlConnection conn = null;
try
{
  conn = new SqlConnection("...");
  // ...
}
finally
{
  if (conn != null) conn.Close();
}