Retrieving Network Errors
Windows NT Only

When one of the WNet functions returns WN_EXTENDED_ERROR, an application can call the WNetGetLastError function to get more information about the error that occurred. This information is usually specific to the network provider. 

The following example illustrates an application-defined error-handling function (NetErrorHandler) that takes three arguments: a window handle, the error code returned by one of the WNet functions, and the name of the function that produced the error. If the error code is WN_EXTENDED_ERROR, NetErrorHandler calls WNetGetLastError to get extended error information. 

BOOL WINAPI NetErrorHandler(HWND hwnd, 
                            DWORD dwErrorCode, 
                            LPSTR lpszFunction) 
{ 
    DWORD dwWNetResult, dwLastError; 
    CHAR szError[ 256 ]; 
    CHAR szCaption[ 256 ]; 
    CHAR szDescription[ 256 ]; 
    CHAR szProvider[ 256 ]; 
 
    // The following code performs standard error-handling. 
 
    if (dwErrorCode != ERROR_EXTENDED_ERROR) 
    { 
        wsprintf((LPSTR) szError, "%s failed; \nResult is %ld", 
            lpszFunction, dwErrorCode); 
        wsprintf((LPSTR) szCaption, "%s error", lpszFunction); 
        MessageBox(hwnd, (LPSTR) szError, (LPSTR) szCaption, MB_OK); 
        return TRUE; 
    } 
 
    // The following code performs error-handling when the 
    // ERROR_EXTENDED_ERROR return value indicates that WNetGetLastError 
    // can retrieve additional information. 
 
    else 
    { 
        dwWNetResult = WNetGetLastError(&dwLastError, 
            (LPSTR) szDescription,  // buffer for error description 
            sizeof(szDescription), 
            (LPSTR) szProvider,     // buffer for provider name 
            sizeof(szProvider)); 
 
        if(dwWNetResult != NO_ERROR) { 
            wsprintf((LPSTR) szError, 
                "WNetGetLastError failed; error %ld", dwWNetResult); 
            MessageBox(hwnd, (LPSTR) szError, 
                "WNetGetLastError", MB_OK); 
            return FALSE; 
        } 
 
        wsprintf((LPSTR) szError, 
            "%s failed with code %ld;\n%s", 
            (LPSTR) szProvider, dwLastError, (LPSTR) szDescription); 
        wsprintf((LPSTR) szCaption, "%s error", lpszFunction); 
        MessageBox(hwnd, (LPSTR) szError, (LPSTR) szCaption, MB_OK); 
        return TRUE; 
    } 
}