解释SQL异常

Question

In my application, I have a data access layer that abstracts the other layers from communication to the database.

Whenever an exception is caught, I log the exception stack trace to help pinpoint the issue, and then handle the exception. This is all fine and dandy, except when it comes to connection problems. Occasionally, the communication to the database is lost, and my log file is drowned in stack traces. In this case, I simply want to log that communication was lost, and whenever communication is restored, I want to log that as well.

This is an issue, because I can't seem to understand the SQL Exception codes. What I would like to do is log connection loss whenever a connection based exception is caught, and log connection restore whenever I can successfully create a new connection. Looking at the log right now, I see that whenever the server is restarted, I catch an exception with number 6005. According to the reference this number indicates:

SHUTDOWN is in progress

This is the exception's message as well, so the exception matches the error code.

Scrolling further down, I see an exception with 10054 with the following message:

A connection was successfully established with the server, but then an error occurred during the pre-login handshake.

but the reference says that error 10054 indicates

The data value for one or more columns overflowed the type used by the provider.

This gives me an impression that if I assume that error 10054 is a login issue, I might have problems in case the overflow exception is ever thrown. I'd like to note that in my application, the overflow exception should never occur, but i don't want to take that assumption to exception handling, because it is in fact an exception to the regular execution.

Answer 1

You could simplify this and just create a method to open the database connection for you and catch/handle errors if it fails. Something like this (untested) :

public bool OpenConnection ()
{
    try 
    {
        using(var connection = new ADODB.Connection(...)) 
        {
            connection.Open();
            return true;
        }
    } 
    catch (Exception ex)
    {
        // log the exception
        return false;
    }
}

Then in your code call that method and handle cases when the connection fails to open:

if (OpenConnection() == false)
{
    // Log / handle / throw error to state the connection failed to open
}
else
{
    // Run the code
}

This approach would still log SQL Exceptions but it will avoid the need to interpret individual exceptions. Your concern is with connecting to the database, which will either work or not, so this will give you that information and log the exact error.