SQLite database is locked #2

Question

I have 2 queries but on update cmd2.ExecuteNonQuery(); it throws an exception "database is locked":

if (txt_balance.Text != "")
{
    using ( SQLiteConnection con = new SQLiteConnection(obj.getDbSourceFile))
    {
        con.Open();
        SQLiteCommand cmd1 = new SQLiteCommand("SELECT [supplier_balance] FROM [s_supplier] where supplier_name='" + comboPurchaseSupplier.Text + "'", con);
        SQLiteDataReader DR = cmd1.ExecuteReader();
        // hfcconn.Close();
        if (DR.HasRows)
        {
            if (DR.Read())
            {
                //hfcconn.Open();
                using (SQLiteConnection con2 = new SQLiteConnection(obj.getDbSourceFile))
                {
                    SQLiteCommand cmd2 = new SQLiteCommand("update [s_supplier] set supplier_balance=" + (DR.GetInt32(0) + Convert.ToInt32(txt_balance.Text)) + " where supplier_name='" + comboPurchaseSupplier.Text + "'", con2);

                    con2.Open();
                    cmd2.ExecuteNonQuery();


                    DR.Dispose();
                    // con.Close();
                }
            }
        }
     // con.Close();
     }
}

Answer 1

The problem is that you are using two connections.

Connections (and their transactions) are isolated from each other, so the second connection cannot update a table on which the first connection still has an open reader.