Question

How can the return error code be specified on application exit? If this were a VC++ application, I could use the SetLastError(ERROR_ACCESS_DENIED) — return GetLastError() APIs. Is there a way to do this in C#?

  static int Main(string[] args)
  {
     Tool.Args = args;

     Application.EnableVisualStyles();
     Application.SetCompatibleTextRenderingDefault(false);
     Application.Run(new Download_Tool());

     return Tool.ErrorCode;
  }

How can the Tool.ErrorCode value be set intelligably? If I try something like Tool.ErrorCode = ERROR_ACCESS_DENIED, I get an error, “The name ERROR_ACCESS_DENIED does not exist in the current context.” Thanks.

ADDITIONAL INFORMATION

My example is over-simplified. Is there a way to something like this:

Tool.ErrorCode = ERROR_ACCESS_DENIED;
return Tool.ErrorCode;

…which generates a compile-error, rather than this:

Tool.ErrorCode = 5;
return Tool.ErrorCode;

…which works, but uses a “magic number.” I’d like to avoid the use of magic numbers.

Answer 1

http://msdn.microsoft.com/en-us/library/system.environment.exit.aspx

Environment.Exit(exitCode)

Update

The reason why you get a compile error with “ERROR_ACCESS_DENIED” is because you have not defined it. You need to define it yourself:

const int ERROR_ACCESS_DENIED = 5;

Then you can use:

Environment.Exit(ERROR_ACCESS_DENIED)

Update 2

If you are looking for a ready-made set of winerror.h constants for your C# needs, then here it is:

http://www.pinvoke.net/default.aspx/Constants/WINERROR.html

I would probably modify the GetErrorName(…) method to do some caching though, e.g.:

private static Dictionary<int, string> _FieldLookup;

public static bool TryGetErrorName(int result, out string errorName)
{
    if (_FieldLookup == null)
    {
        Dictionary<int, string> tmpLookup = new Dictionary<int, string>();

        FieldInfo[] fields = typeof(ResultWin32).GetFields();

        foreach (FieldInfo field in fields)
        {
            int errorCode = (int)field.GetValue(null);

            tmpLookup.Add(errorCode, field.Name);
        }

        _FieldLookup = tmpLookup;
    }

    return _FieldLookup.TryGetValue(result, out errorName);
}