困扰我好久的问题！很急，谢谢帮忙

Question

public   DataTable   dguser_SelectedIndexChanged()
        {
                string   SqlString   =   "select   *   from   mis   where dm=@dim";                SqlConnection   uSqlConnection   =   new   SqlConnection("Data   Source=localhost;Initial   Catalog=web;User   ID=sa;Password=sa");                SqlCommand   cmd   =   new   SqlCommand(SqlString,   uSqlConnection);
                cmd.CommandType   =   CommandType.Text;                cmd.Parameters.Add("@dim",   SqlDbType.VarChar,   50);
                cmd.Parameters["@dim"].Value   =   dmList.SelectedItem.Value;
               
                SqlDataAdapter   sd   =   new   SqlDataAdapter(cmd);
                DataSet   ds   =   new   DataSet();
                sd.Fill(ds);
                return   ds.Tables[0];
                //cmd.Connection.Close();        }

Answer 1

[code=C #]
           public DataTable dguser_SelectedIndexChanged()
            {
                string SqlString = " SELECT * FROM mis where dm =@dm";                SqlConnection uSqlConnection = new SqlConnection("Data Source=localhost;Initial Catalog=web;User ID=sa;Password=sa");                SqlCommand cmd = new SqlCommand(SqlString, uSqlConnection);
                cmd.CommandType = CommandType.Text;
                cmd.Parameters.Add("@dm", SqlDbType.VarChar, 50);
                cmd.Parameters["@dm"].Value = DMList;
                SqlDataAdapter sd = new SqlDataAdapter(cmd);
                DataSet ds = new DataSet();
                sd.Fill(ds);
                return ds.Tables[0];
            }[/code]在sd.Fill(ds);处会提示：
"被准备语句'(@dm varchar(50))select*from mis where dm= @dm'需要参数@dm,但未提供该参数。"上一个问题也是这样子。麻烦再帮一下忙！谢了！