mycmd.Parameters.Add("@name", SqlDbType.VarChar, 20).Value = this.txtname.Text.Trim();

这句话的意思是什么哦？请高手详细解释一下，谢谢了

补充一下代码：
SqlConnection myconn = getconnection();
            myconn.Open();
            Label1.Text = "连接成功";
            string sqlstr = "select * from news where name=@name";
            SqlCommand mycmd = new SqlCommand(sqlstr, myconn);
            mycmd.Parameters.Add("@name", SqlDbType.VarChar, 20).Value = this.txtname.Text.Trim();
            SqlDataAdapter myda = new SqlDataAdapter(mycmd);
            DataSet myds = new DataSet();
            myda.Fill(myds);