Sqlexception 判斷錯誤類型

use a try catch block like this: 

try
{
  ...
  ...
}
catch (SqlException ex)
{
  switch (ex.Number) 
    { 
        case 4060: // Invalid Database 
                  ....
                  break;
        case 18456: // Login Failed 
                  ....
                  break;
        case 547: // ForeignKey Violation 
                  ....
                  break;
        case 2627: // Unique Index/ Primary key Violation/ Constriant Violation 
                  ....
                  break;
        case 2601: // Unique Index/Constriant Violation 
                  ....
                  break;
        default: 
                  ....
                  break;    
       } 
}