如何将一个类中的SQL异常编号抛出到另一个类中的常规异常中？ C＃

Question

I want to throw an SqlException Number from one class into a regular Exception in another.

So I want something like this (pseudo code)

SQL Class

catch (SqlException sqlex)
{
    if (sqlex.Number == 911)
    {
        throw new Exception("There is no database to be found");
    }
    if (sqlex.Number == 1510)
    {
        throw new Exception("There isn't a database attached");
    }
    if (sqlex.Number == 5120)
    {
        throw;  //("You do not have permissions to attach this file.");
    }
    else
    {
        throw sqlex;
    }
}

Class B

if (ex == 5120)
{
    dostuff();
}

The 'dirty' way around it is that I could just throw a new Exception with the message "5120" and then read it from there but I don't think that's the best way?

Thanks,

Answer 1

Normally, code that could potentially throw an exception is wrapped with try{} catch{} block on a next layer and this is combined with custom Exceptions. For possible multiple exceptions you can use multiple catch blocks:

public class NoPermissionSqlException : Exception
{
    public NoPermissionSqlException(string message) : base(message) {}
    // ... implement other constructors
}

And use it :

public void MyMethod()  // method that could throw an exception
{
   if (sqlex.Number == 5120)
   {
       throw new NoPermissionSqlException("You do not have permissions to attach this file.");
   }
}

And calling code:

try
{
   MyMethod();   
}
catch(NoPermissionSqlException ex)
{       
   // ... handle no permission error here
   dostuff();
}
catch(Exception ex)
{
   // ... default handler
}