SQL条目仅显示在DataGridSet上

Question

我用C＃开发了一个带有SQL数据库的winforms应用程序。一旦我将数据输入表单并按下显示按钮，它就会显示在datagridview上，但是一旦我重新启动应用程序，数据就不会显示在网格上。

这是添加新数据的代码。

            if (textBox1.Text != "" && textBox2.Text != "" && textBox3.Text != "")
        {
            con = new SqlConnection();
            con.ConnectionString = @"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\shenal.mdf;Integrated Security=True";
            cmd = new SqlCommand("insert into [dbo].[user] (Id,username,password) values(@id,@name,@state)", con);
           // cmd.CommandText = "insert into [dbo].[user] (Id,username,password) values(@id,@name,@state)";
            cmd.Parameters.AddWithValue("@id", textBox1.Text);
            cmd.Parameters.AddWithValue("@name", textBox2.Text);
            cmd.Parameters.AddWithValue("@state", textBox3.Text);
            con.Open();
            cmd.ExecuteNonQuery();
            con.Close();
            MessageBox.Show("Record Inserted Successfully");
        }
        else {
            MessageBox.Show("Please Provide Details!");
        }

这是检索它的代码。

        con = new SqlConnection();
        con.ConnectionString = @"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\shenal.mdf;Integrated Security=True";
        con.Open();
        DataTable dt = new DataTable();
        adapt = new SqlDataAdapter("select * from [dbo].[user]", con);
        adapt.Fill(dt);
        dataGridView1.DataSource = dt;
        con.Close();