The system failed to establish a connection

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I am working on pos system and all things are working fine even I have added MySQL workbench database in visual studio in server explorer but when I try to connect my software with database connection so am getting error The system failed to establish a connection please help see my code and please point out me where I am wrong and what is the best way to resolve this problem thanks

What I have tried:

C#

private string TstServerMySQL;
    private string TstPortMySQL;
    private string TstUserNameMySQL;
    private string TstPwdMySQL;
    private string TstDBNameMySQL;

    private void cmdTest_Click(object sender, EventArgs e)
    {
        //Test database connection

        TstServerMySQL = txtServerHost.Text;
        TstPortMySQL = txtPort.Text;
        TstUserNameMySQL = txtUserName.Text;
        TstPwdMySQL = txtPassword.Text;
        TstDBNameMySQL = txtDatabase.Text;

        try
        {
            SQLConn.conn.ConnectionString = "Server = '" + TstServerMySQL + "';  " + "Port = '" + TstPortMySQL + "';" + "user id = '" + TstUserNameMySQL + "';   " + "password = '" + TstPwdMySQL + "'; " + "Database = '" + TstDBNameMySQL + "'";
            SQLConn.conn.Open();
            Interaction.MsgBox("Test connection successful", MsgBoxStyle.Information, "Database Settings");

        }
        catch
        { 
            Interaction.MsgBox("The system failed to establish a connection", MsgBoxStyle.Information, "Database Settings");
        }
        SQLConn.DisconnMy();
    }

Posted 14-Jul-19 5:23am

Member 9983063

Updated 14-Jul-19 9:27am

Blutfaust

v2

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Patrice T · Answer 1 · 2019-07-14T05:59:00

Quote:
please help see my code and please point out me where I am wrong and what is the best way to resolve this problem thanks

What kind of help do you expect ?
The connection string depend on user input, how can we guess what is the connection string ?

Already 128 question and you still don't know how to make a question answerable.

Dave Kreskowiak · Answer 2 · 2019-07-14T09:27:00

That code you wrote to assemble a connection string is absolute garbage.

Besides not doing any input validation at all, you're using string concatenation to build the connection string, which makes your code pretty much unreadable and a pain in the ass to debug. Use string interpolation instead and it gets much easier. (You also don't need all the damn spaces and the single quotes!)

C#

string connStr = $"Server={TstServerMySQL};Port={TstPortMySQL};Usser Id={TstUserNameMySQL};Password={TstPwdMySQL};Database={TstDBNameMySQL}";
SQLConn.conn.ConnectionString = connStr;

Also, breaking the building of the connection string out into it's own variable makes it easier to see the content of the connection string in the debugger before assigning it to the connection object.

The system failed to establish a connection

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