ASP.NET数据插入与更新！

dsQuyMst.Tables["QuyMst"].Rows[0]["SHDOCO"] = "1111";//这句报错（未将对象引用设置到对象的实例。）
这知道是什么原因？
高人指点~~~

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.Collections.Generic;

public partial class P81001A : System.Web.UI.Page
{
  DataSet dsQuyMst;
  // SqlDataAdapter da;
  protected void Page_Load(object sender, EventArgs e)
  {
  if (!Page.IsPostBack)
  {
  LoadData();
  }
  //Menu1_MenuItemClick(object,e);
  //DropDownList1_SelectedIndexChanged(object,e);
   


  }

  private void LoadData()
  {
  DataSet ds = new DataSet();//
  SqlConnection con = new SqlConnection();
  con.ConnectionString = GetConnectionStr();
  con.Open();
  string strsql = "select SHTYPENO,SHTYPENAME from f81101";
  SqlCommand sqlcmd = new SqlCommand(strsql, con);