Passing dataset between ASP.NET Web Forms

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  • zhshqzyc
    New Member
    • Feb 2008
    • 9
    #1

    Passing dataset between ASP.NET Web Forms

    I am going to past a dataset from First.aspx to Second.aspx.
    A whole table will be displayed on First.aspx and partial columns
    will be displayed on Second.aspx.
    First.aspx view in browser works well if I exclude Second.aspx. But when Second.aspx is included in the project, an error happens.
    I can't find what is wrong in my code.

    Code:
     System.NullReferenceException was unhandled by user code
  Message="Object reference not set to an instance of an object."
    First.aspx.cs
    Code:
    namespace FirstPage
{
    public partial class GetStrings : System.Web.UI.Page
    {
        getStrings g = new getStrings();
        protected void Page_Load(object sender, EventArgs e)
        {
            string strConnectionString = ConfigurationManager.ConnectionStrings["SqlConnectionString"].ConnectionString;
            SqlConnection myConnection = new SqlConnection(strConnectionString);
            DataSet myDataSet = new DataSet();
            try
            {
                myConnection.Open();
                // create the data
                GenerateDataSet(myDataSet, myConnection);
            }
            finally
            {
                myConnection.Close();
                // bind each to table to a grid

            }
            Session["myds"] = myDataSet;
            // databind the page 
            GridView1.DataSource = myDataSet.Tables["Weather"];
            GridView1.DataBind();
        }
    and
    Second.aspx.cs
    Code:
    using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
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 FirstPage;

public partial class Second : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        DataSet ds = (DataSet)Session["myds"];
        FillTable(ds);
        GridView1.DataSource = ds.Tables["Index"];
        GridView1.DataBind();
    }

    void FillTable(DataSet dset)
    {
        DataTable indexTable = dset.Tables.Add("Index");

        DataColumn indexID =
            indexTable.Columns.Add("State", typeof(string));
        indexTable.Columns.Add("Division", typeof(string));
        indexTable.Columns.Add("MOIST_INDEX", typeof(string));
        indexTable.Columns.Add("DROUGHT_INDEX", typeof(string));
    }
}
    Second.aspx
    Code:
    <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Second.aspx.cs" Inherits="Second" %>
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<%@ Reference Page="First.aspx" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:GridView ID="GridView1" runat="server">
        </asp:GridView>
    </div>
    </form>
</body>
</html>
    Any help will be appreciated.
    Tags: None
    • nateraaaa
      Recognized Expert Contributor
      • May 2007
      • 664
      #2
      Second.aspx.cs

      Code: ( text )
      using System;
      using System.Data;
      using System.Data.Sql Client;
      using System.Configur ation;
      using System.Web;
      using System.Web.Secu rity;
      using System.Web.UI;
      using System.Web.UI.W ebControls;
      using System.Web.UI.W ebControls.WebP arts;
      using System.Web.UI.H tmlControls;
      using FirstPage;

      public partial class Second : System.Web.UI.P age
      {
      protected void Page_Load(objec t sender, EventArgs e)
      {
      DataSet ds = (DataSet)Sessio n["myds"];
      FillTable(ds);
      GridView1.DataS ource = ds.Tables["Index"];
      GridView1.DataB ind();
      }

      void FillTable(DataS et dset)
      {
      DataTable indexTable = dset.Tables.Add ("Index");

      DataColumn indexID =
      indexTable.Colu mns.Add("State" , typeof(string)) ;
      indexTable.Colu mns.Add("Divisi on", typeof(string)) ;
      indexTable.Colu mns.Add("MOIST_ INDEX", typeof(string)) ;
      indexTable.Colu mns.Add("DROUGH T_INDEX", typeof(string)) ;
      }
      }
      I believe what is happening is table Index does not exist in your dataset so GridView1.DataS ource = ds.Tables["Index"];
      is creating an object reference not set to an instance of an object error. There are a few ways to change your code to eliminate this error. Here a 2 options.
      1. Change your parameter to include the out keyword
      [CODE=cpp]public void FillTable(out DataSet dset)
      {
      DataTable indexTable = dset.Tables.Add ("Index");

      DataColumn indexID =
      indexTable.Colu mns.Add("State" , typeof(string)) ;
      indexTable.Colu mns.Add("Divisi on", typeof(string)) ;
      indexTable.Colu mns.Add("MOIST_ INDEX", typeof(string)) ;
      indexTable.Colu mns.Add("DROUGH T_INDEX", typeof(string)) ;
      }[/CODE]

      2. Change your method to return a DataSet and then add the DataTable to your DataSet.
      [CODE=cpp]public DataSet FillTable(DataS et dset)
      {
      DataTable indexTable = dset.Tables.Add ("Index");

      DataColumn indexID =
      indexTable.Colu mns.Add("State" , typeof(string)) ;
      indexTable.Colu mns.Add("Divisi on", typeof(string)) ;
      indexTable.Colu mns.Add("MOIST_ INDEX", typeof(string)) ;
      indexTable.Colu mns.Add("DROUGH T_INDEX", typeof(string)) ;

      return dset;
      }
      protected void Page_Load(objec t sender, EventArgs e)
      {
      DataSet ds = (DataSet)Sessio n["myds"];
      ds = FillTable(ds);
      GridView1.DataS ource = ds.Tables["Index"];
      GridView1.DataB ind();
      }
      [/CODE]

      Nathan

        Comment

        • zhshqzyc
          New Member
          • Feb 2008
          • 9
          #3
          Thanks!
          I will try it.

            Comment

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