在Windows窗体中更新SQL Server Express数据库时出错

Question

This is my problem:

I am creating an application in C# using Visual Studio 2010. In one of the modules of the application, I have to update an existing table and insert into another table. Both tables are created.

Problem is when I don't close the total application, it updates and inserts into the tables perfectly, but when I close the application and open it again all the values are reset.

I think that only the data set is being updated and not the actual database.

I want to know how to actually update the database.

My code looks somewhat like this:

    System.Data.SqlClient.SqlConnection con;                      
    System.Data.SqlClient.SqlCommand cmd,cmd1,cmd2;

    private void Form3_Load(object sender, EventArgs e)
    {
        con = new System.Data.SqlClient.SqlConnection();
        con.ConnectionString = "Data Source=.\\SQLEXPRESS;AttachDbFilename=|DataDirectory|\\pharmacy.mdf;Integrated Security=True;User Instance=True";
        con.Open();
        MessageBox.Show("Connection successful!");
    }

    private void button1_Click(object sender, EventArgs e)
    {
        cmd1 = new System.Data.SqlClient.SqlCommand("Select med_id from stock where med_id= " + textBox1.Text + ";", con);
        object result = cmd.ExecuteScalar();
        if (result == null)
        {
            cmd = new System.Data.SqlClient.SqlCommand("insert into stock values('" + textBox1.Text + "','" + textBox2.Text + "','" + textBox3.Text + "','" + textBox4.Text + "','" + textBox5.Text + "','" + textBox6.Text + "','" + textBox7.Text + "','" + textBox8.Text + "','" + textBox9.Text + "');", con);
            cmd.ExecuteNonQuery();
        }
        else
        {
            cmd2 = new System.Data.SqlClient.SqlCommand("alter table stock set current_stock = (select current_stock from stock where med_id=" + textBox1.Text + ";) + "+ textBox8.Text +" where med_id="+textBox1.Text+";",con);
         }
            cmd2.ExecuteNonQuery();     
    }

Answer 1

These steps worked for me, I'm using Visual Studio Express 2013 for Windows Desktop:

Step 1: Go to database explorer, right click database name (mdf file), select modify connections, select Browse, within your project folder, go into the bin folder, then go into the Debug folder, select the mdf file in the debug folder, select Test Connection to ensure connection succeeds, then click OK

Next, go to properties of the database (mdf file), click the connection string box in the properties explorer menu, copy the data source file path in the connection string box

Step 2: In the Solutions Explorer box, double click 'Properties', go to Settings option, Insert Name - (can be anything you want, I named mine EmployeeConnString) Insert Type - In the dropdown box, select connection string Insert Scope - in the dropdown box, select application Insert Value - right-click paste (previously copied file path), press enter You can exit this tab

Step 3: Go back to the solutions explorer box and select the database file in your vs project(mdf file), Go to the properties explorer window to the copy to output directory option, change "Copy Always" to "Copy Never" or "Do Not Copy",

These steps worked for me and now everything I enter updates correctly, as well as when i re-run the application, the updated data shows in the new form box.

Answer 2

As usual - upon running, Visual Studio makes a copy of your database file. Then, you work with that copy, you update records there. When you invoke the application again, the original file is copied over the one you made changes into.