App.startup路径在我的Visual Studio项目中不起作用？

Question

There is no error in this code but when i insert the values,they are not actually inserted in database. Here is my connection string class :

      public class DBConn
   {

   public static SqlConnection GetConnection()
   {

      string sDBPath = Application.StartupPath + @"\App_Data\Database3.mdf";

      string connStr = @"Data Source=.\SQLEXPRESS;AttachDbFilename='" + sDBPath + "';Integrated Security=True;User Instance=True";

       return new SqlConnection(connStr);
   }
}

and in this class i call the connection string class :

        string query = "INSERT INTO Table1 VALUES('" + textBox1.Text + "')";
        SqlConnection con = DBConn.GetConnection();

        SqlCommand com = new SqlCommand(query,con);
        con.Open();
        using (con)
        {
            com.ExecuteNonQuery();
            MessageBox.Show("Insert");
        }

Answer 1

using (SqlConnection connection = new SqlConnection(connectionString))
{
    connection.Open();
    // Do work here; connection closed on following line.
}

• Your use of the using statement is not recommended and leads to
  problems. You have to instantiate the resource object inside the
  using statement! It's scope or lifetime is now limited to the
  statement block and will be properly garbage collected. The way you
  use it (by passing an already instantiated object into the using
  statement) the objects remains valid although not properly accessible since it was never properly closed or disposed. MSDN - using statement . So instead of creating the connection and passing it around your application (bad practice) you should create the connection settings (connection string) and the query and use them to create a connection resource inside a using statement everytime you need a connection. This way the resource is always correctly disposed. The provided link gives you an example how to use a using statement.

• Check your connection string well if all provided information is valid or all needed information is provided (eg username and password).

• Check database settings (eg permissions)

• SqlConnection class has an event called InfoMessage . In case the connection produces any warnings or errors you will get notified.

• Check your database (eg log) for the occurance of errors.