asp.net dispose inside a class

Question

Before return dt i want destroy sda

How destroy an Object with Dispose - inside the class dbConnect ?

  public class dbConnect
    {

    // othee code 

    public DataTable SetQuery(string constr, DataTable dt, string sSql)
        {              
            using (MySqlConnection con = new MySqlConnection(constr))
            {
                //sda = null
                using (MySqlDataAdapter sda = new MySqlDataAdapter())
                    {
                        try
                        {
                            cmd.Connection = con;
                            sda.SelectCommand = cmd;
                            sda.Fill(dt);
                        }

                        finally
                        {
                            if (sda != null)
                                sda.Dispose();
                            //why the sda is not = null ?
                        }

                        return dt;
                    }             
            }              
        }

What is the correct procedure for destroy object (not class) ?

Answer 1

• Using Dispose() doesn't mean your variable will become null, it's you who chooses wheither your variable should stop referencing something (so it's you who must set it to null).
• You don't need to call Dispose() when you use using on a variable, it will be called automatically at the end (see: https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/using-statement).

Answer 2

Since you make use of the using statement for sda, the Dispose would be called under the hood once you don't need it anymore.

For further info please have look here.