Database is being used by another process … but what process?

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 pro

Answer 1

This is the rewritten code, using the "Using" statements. When I execute the program and click on Insert Record Into SQL File, off it goes, completes the process with myCount = 1 (though I'm not 100% sure that it is actually doing a physical Write, am I missing a command that actually "commits" the update ?!?) and re-displays the Form.

If I then click on Insert Record Into SQL File again, I get an error as follows :

SqlException was unhandled

Cannot open user default database. Login failed. Login failed for user 'MEDESKTOP\Gary'.

This is the program (I am the only user on this PC and have full Admin rights, the "State" of the database at this point is, according to Properties, Closed, so it looks like the first pass through the code did as was expected ...

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace MySqlTest
{
public partial class Form1 : Form
{
    int myCount;
    string myDBlocation = @"Data Source=MEDESKTOP;AttachDbFilename=|DataDirectory|\mySQLtest.mdf;Integrated Security=True;User Instance=False";

    public Form1()
    {
        InitializeComponent();

    }

    private void button2_Click(object sender, EventArgs e)
    {
        myCount++;
        MessageBox.Show("myCount = " + myCount.ToString());
        //Insert Record Into  SQL File
        myDB_Insert();
    }

    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 SQL File
    }

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

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void Form1_Close(object sender, EventArgs e)
    {

    }

    void myDB_Insert()
    {
        using (SqlConnection myDB = new SqlConnection(myDBlocation))
        using (SqlCommand mySqlCmd = myDB.CreateCommand())
        {
            myDB.Open(); **<<< Program fails here, 2nd time through**
            mySqlCmd.CommandText = "INSERT INTO Parent (ParentName) VALUES(@ParentNameValue)";
            mySqlCmd.Parameters.AddWithValue("@ParentNameValue", myCount);
            mySqlCmd.ExecuteNonQuery();
            myDB.Close();
        }
        return;
    }

    void myDB_Close()
    {
        using (SqlConnection myDB = new SqlConnection(myDBlocation))
        using (SqlCommand mySqlCmd = new SqlCommand())
        {
            myDB.Close();
        }
        return;
    }

}
}

I don't understand why I am suddenly losing access to my own file that I am already using ?!?