Question

I have written a very small C# program, that uses a very small SQL Server database, purely for some learning & testing purposes. The database is used in this one new project and nowhere else. However, I am getting problems whilst running Debugs where the program will not run, because the database “is being used by another process”.

If I reboot my machine, it will work again, and then after a few test runs I will get the same problem again.

I have found many, many similar problems reported all over the Internet, but can find no definitive answer as to how to resolve this problem. Firstly, how do I find out what “other process” is using my .mdf & .ldf files ? Then, how do I get these files released & not held in order to stop this happening time after time after time ?!?

I am new to VS2010, SQL Server & C#, so please be quite descriptive in any replies you give me !!!

This is my code, as you can see, you couldn’t get anything much more basic, I certainly shouldn’t be running into so many problems !!!

namespace MySqlTest
{
    public partial class Form1 : Form
    {
        SqlConnection myDB = new SqlConnection(@"Data Source=MEDESKTOP;AttachDbFilename=|DataDirectory|\SqlTestDB.mdf;Initial Catalog=MySqlDB;Integrated Security=True");
        SqlDataAdapter myDA = new SqlDataAdapter();
        SqlCommand mySqlCmd = new SqlCommand();

        string mySQLcmd;
        int myCount;

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            MessageBox.Show("myDB state = " + myDB.State.ToString());
            //Open SQL File
            myDB.Open();
            MessageBox.Show("myDB state = " + myDB.State.ToString());
        }

        private void button2_Click(object sender, EventArgs e)
        {
            myCount++;
            MessageBox.Show("myCount = " + myCount.ToString());
            //Insert Record Into  SQL File
            mySqlCmd.Connection = myDB;
            mySqlCmd.CommandText = "INSERT INTO Parent(ParentName) Values(myCount)";
            myDA = new SqlDataAdapter(mySqlCmd);
            mySqlCmd.ExecuteNonQuery();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            //Read Record From SQL File
        }

        private void button4_Click(object sender, EventArgs e)
        {
            //Read All Records From SQL File
        }

        private void button5_Click(object sender, EventArgs e)
        {
            //Delete Record From DQL File
        }

        private void button6_Click(object sender, EventArgs e)
        {
            MessageBox.Show("myDB state = " + myDB.State.ToString());
            //Close SQL File
            myDB.Close();
            MessageBox.Show("myDB state = " + myDB.State.ToString());
        }

        private void button7_Click(object sender, EventArgs e)
        {
            //Quit
            this.Close();
        }
    }
}

Answer 1

The most likely options:

1. A previous (crashed) instance of your program
2. Visual Studio (with a Table designer open or something similar)

You can check 1) with TaskManager and 2) by looking in Server Explorer. Your db should show a small red cross meaning ‘closed’.

And you should rewrite your code to close connections ASAP. Use try/finally or using(){ } blocks.