C# connection.Open() exception

Question

I am trying to connect to my database on localhost but for some reason, it throws an exception, and I can't find out why and where.

private void Initialize()
    {
        server = "localhost";
        database = "dbname";
        uid = "uname";
        password = "pass";
        string connectionString;
        connectionString = "SERVER=" + server + ";" + "DATABASE=" +
        database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";";

        connection = new SqlConnection(connectionString);
    }

This is my initialize function; my problem is with:

    private bool OpenConnection()
    {
        try
        {
            connection.Open();
            return true;
        }
             ...

When I debug the program, it stays on "connection.Open();" line for a while, then I see "Exception thrown: 'System.Data.SqlClient.SqlException' in System.Data.dll" on console. But it's not crashing, just skipping.

Is there an inner exception to that exception, and what are the exception message(s)? — hatchet - done with SOverflow
– hatchet - done with SOverflow, Commented Apr 19, 2017 at 22:04
after your try {} you chould have catch (Exception ex) { /* put break point here to view the contents of your exception (ex) */ } — MBurnham
– MBurnham, Commented Apr 19, 2017 at 22:05
If you aren't stopping on the exception, that's a problem and I'd start there: stackoverflow.com/questions/16970642/… Once you can see what the exception actually is, you can give us more information. — Dave Lucre
– Dave Lucre, Commented Apr 19, 2017 at 22:05

Steve · Accepted Answer · 2017-04-21 13:38:08Z

3

If you want to open a connection with MySql, then you don't use the classes from System.Data.SqlClient namespace but with the classes from MySql.Data.MySqlClient

These classes are MySqlConnection, MySqlCommand, MySqlDataReader etc...
If you try to use the SqlConnection class you receive this error if the database to open is MySql because it can only work with the Sql Server, Sql Server Express or LocalDB database systems.

connection = new MySqlConnection(connectionString);

Of course, to use the MySql.Data.MySqlClient namespace you need to download and install the MySql NET Connector and then add a reference into your project to the assembly MySql.Data.dll (and add the using MySql.Data.MySqlClient to the top of each cs file that needs to use these classes)

edited Apr 21, 2017 at 13:38

answered Apr 19, 2017 at 22:29

Steve

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4 Comments

osumatu Over a year ago

will you marry me?

MBurnham Over a year ago

Please not that this requires the use of a third party namespace, MySql.Data is not provided in the .NET Framework by default. It is an ADO.NET driver provided by MySql

Rahul Over a year ago

LOL ... didn't knew answering in SO can even get you marriage proposal ... Stevee you are so lucky ... :)

Steve Over a year ago

@Rahul it depends :-)

MBurnham · Accepted Answer · 2017-04-19 22:10:27Z

0

It is not crashing because you are opening the connection inside of a try-catch block, so the program thinks you are handling the exception. If you want it to crash, get rid of the try-catch block. (This would be a bad user experience.)

Alternatively, after your try-catch, you could check the connection is valid and then do something if it isn't.

if ((connection == null) || (connection.State != ConnectionState.Open)) { 
    /* do something here to indicate to the user there was an issue.
}

answered Apr 19, 2017 at 22:10

MBurnham

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3 Comments

osumatu Over a year ago

i see, the problem is i can't open the connection so it returns null. but why is this happening i just can't understand this.

MBurnham Over a year ago

@osumatu you will need to provide us with the message from the exception (ex.message) for us to possibly answer that

YankTHEcode Over a year ago

In order to understand why it returns null, add a catch block as mentioned by @MBurnham and see what goes in there. It should tell you whether the credentials are incorrect or the user doesn't have the right kind of access.

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