Store a timer value in a database? c#

Question

I have a global variable which is set up for the timer, "I", the program I'm creating has a user play a game level and store their level time in a database with other users. This is what I have already.

public static class Global

{

    public static int I = 0; 

}

^ this is the global variable for the timer.

        SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\Adam\Documents\Data2.mdf;Integrated Security=True;Connect Timeout=30"); 

        SqlDataAdapter sad = new SqlDataAdapter("Select Count(*) From Login where Username= '" + txtUsername.Text + "' and Password='" + txtPassword.Text + "'", con); 

        SqlCommand cmd = new SqlCommand("INSERT INTO HighScore (Username, Score) VALUES(@Username,@Score)", con);

        DataTable dt = new DataTable(); //empty table

        sad.Fill(dt); 

        if (dt.Rows[0][0].ToString() == "1")   

        {

            con.Open();

            cmd.Parameters.AddWithValue("@USERNAME", txtUsername.Text);

            cmd.Parameters.AddWithValue("@Score", Global.I);

        }

        else // else it will display this error

        {

            MessageBox.Show("Please enter the correct login details");

        }

^^ this is the code for the end screen of the game, as you can see i've tried taking the Global.I and addwithvalue @Score which is in the HighScore table in my database.
Now when i click the button it doesn't write anything to the database but I don't get any errors when i try and save, this is why i'm confused.
Any help would be appreciated, Thanks.

Answer 1

before executing any command you first must open the connection. You are opening the connection after calling Fill()!!. You will also have to execute cmd. Try:

SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;AttachDbFilename=C:\Users\Adam\Documents\Data2.mdf;Integrated Security=True;Connect Timeout=30"); 
SqlDataAdapter sad = new SqlDataAdapter("Select Count(*) From Login where Username= '" + txtUsername.Text + "' and Password='" + txtPassword.Text + "'", con); 

SqlCommand cmd = new SqlCommand("INSERT INTO HighScore (Username, Score) VALUES(@Username,@Score)", con);
con.Open();
cmd.Parameters.AddWithValue("@USERNAME", txtUsername.Text);
cmd.Parameters.AddWithValue("@Score", Global.I);
DataTable dt = new DataTable(); //empty table
sad.Fill(dt);
cmd.ExecuteNonQuery();

It is also admirable that you know how to correctly use parameters, however you use them only in 1 case instead of both queries.

Store a timer value in a database? c#

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