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9.0

Object reference not set to an instance of an object.

Asked by chris_desborough in Programming for ASP.NET, C# Programming Language

Tags: asp.net c#

Cannot resolve the error I'm receiving - Object reference not set to an instance of an object - for "dt.Rows.Count" in the FindRow method.

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             using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Collections;
 
public partial class Default3 : System.Web.UI.Page
{
 
    static DataTable dt = null;
    static DataRow dr = null;
 
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            Session["counter"] = 0;  // used to increment the 'id' Datatable value
 
            dt = new DataTable();
 
            dt.Columns.Add("id");
            dt.Columns.Add("qtyordered");
            dt.Columns.Add("itemdesc");
            dt.Columns.Add("unitofissue");
            dt.Columns.Add("itemno");
 
            ItemInOrder.DataSource = dt;
            ItemInOrder.DataBind();
 
            lblItemsInOrder.Text = "0";
        }
    }
    protected void btnDelete_Click(object sender, EventArgs e)
    {
        Button b = (Button)sender;
        int id = int.Parse(b.CommandArgument);
        DeletedRows.Add(id);
        ItemInOrder.DeleteRow(id);
    }
    protected void ItemInOrder_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        DataTable dt = (DataTable)ItemInOrder.DataSource;
        foreach (int i in DeletedRows)
        {
            DataRow dr = FindRow(dt, i);
            dt.Rows.Remove(dr);
        }
        ItemInOrder.DataSource = dt;
        ItemInOrder.DataBind();
    }
    private DataRow FindRow(DataTable dt, int id)
    {
      
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            DataRow row = dt.Rows[i];
            int rowId = int.Parse(row["id"].ToString());
            if (rowId == id)
                return row;
        }
        return dr;
    }
    public ArrayList DeletedRows
    {
        get
        {
            if (Session["DELETED_ROW_COLLECTION"] == null)
                Session["DELETED_ROW_COLLECTION"] = new ArrayList();
            return (ArrayList)Session["DELETED_ROW_COLLECTION"];
        }
    }
 
    protected void GridView1_SelectedIndexChanging(Object sender, GridViewSelectEventArgs e)
    {
        GridViewRow row = GridView1.Rows[e.NewSelectedIndex];
 
    }
 
    protected void SqlItemList_Selecting(object sender, SqlDataSourceSelectingEventArgs e)
    {
 
    }
 
    protected void GridView1_SelectedIndexChanged(Object sender, EventArgs e)
    {
 
        // Get the currently selected row using the SelectedRow property.
        GridViewRow row = GridView1.SelectedRow;
 
        // Get the invisible gridview column Item_ID value  
        string idText = ((Label)GridView1.SelectedRow.FindControl("lblItemID")).Text;
 
        // Get the value of the textbox qty template field
        string qtyText = ((TextBox)GridView1.SelectedRow.FindControl("QtyToAdd")).Text;
  
        int maxOrderQty = Convert.ToInt32(row.Cells[6].Text);
        int orderQty = Convert.ToInt32(qtyText);
 
        if (orderQty > maxOrderQty)
        {
            // do something clever
            Response.Write("<script>confirm('Quantity you ordered exceeds the maximum order quantity for this item.')</script>");
            return;
        }
 
        // Insert data into the temp datatable
 
        DataRow dr = dt.NewRow();
 
        int @counter = Convert.ToInt32(Session["counter"]) + 1;
 
        dr["id"] = @counter;
        dr["qtyordered"] = qtyText;
        dr["itemdesc"] = row.Cells[2].Text;
        dr["unitofissue"] = row.Cells[3].Text;
        dr["itemno"] = row.Cells[5].Text;
 
        dt.Rows.Add(dr);
 
        ItemInOrder.DataSource = dt;
        ItemInOrder.DataBind();
 
        Session["counter"] = @counter; 
 
        lblItemsInOrder.Text = @counter.ToString();
 
    }
}
==========================
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default3.aspx.cs" Inherits="Default3"
    EnableEventValidation="false" %>
 
<!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 runat="server">
    <title></title>
    <style type="text/css">
        .style1
        {
            color: #FFFFFF;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:SqlDataSource ID="SqlCategoriesList" runat="server" ConnectionString="<%$ ConnectionStrings:docstoresConnectionString %>"
            SelectCommand="SELECT [Category] FROM [Category] WHERE ([Category] &lt;&gt; @Category) ORDER BY [Category]">
            <SelectParameters>
                <asp:Parameter DefaultValue="ALL ITEMS" Name="Category" Type="String" />
            </SelectParameters>
        </asp:SqlDataSource>
        <asp:SqlDataSource ID="SqlItemList" runat="server" ConnectionString="<%$ ConnectionStrings:docstoresConnectionString %>"
            OnSelecting="SqlItemList_Selecting" SelectCommand="SELECT [Item_ID], [Item_Description], [Item_UnitofIssue], [Item_Image], [Item_ItemNo], [Item_MaxOrderQty] FROM [Items] WHERE (([Item_Active] = @Item_Active) AND ([Item_Category] = @Item_Category))">
            <SelectParameters>
                <asp:Parameter DefaultValue="true" Name="Item_Active" Type="Boolean" />
                <asp:ControlParameter ControlID="ddlCategory" Name="Item_Category" PropertyName="SelectedValue"
                    Type="String" />
            </SelectParameters>
        </asp:SqlDataSource>
        <table style="width: 100%;">
            <tr>
                <td bgcolor="#0033CC">
                    <span class="style1">Select Category</span>
                    <asp:DropDownList ID="ddlCategory" runat="server" AutoPostBack="True" DataSourceID="SqlCategoriesList"
                        DataTextField="Category" DataValueField="Category">
                    </asp:DropDownList>
                </td>
                <td>
                    &nbsp;
                </td>
                <td bgcolor="#0033CC" class="style1">
                    Order Total =
                    <asp:Label ID="lblItemsInOrder" runat="server" Text="Label"></asp:Label>
                </td>
            </tr>
            <tr>
                <td valign="top">
                    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataKeyNames="Item_ID"
                        DataSourceID="SqlItemList" EmptyDataText=".. No items in this category" OnSelectedIndexChanged="GridView1_SelectedIndexChanged"
                        OnSelectedIndexChanging="GridView1_SelectedIndexChanging">
                        <Columns>
                            <asp:CommandField ButtonType="Button" SelectText="Add" ShowSelectButton="True" />
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:TextBox ID="QtyToAdd" runat="server" Width="25px"></asp:TextBox>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:BoundField DataField="Item_Description" HeaderText="Description" SortExpression="Item_Description" />
                            <asp:BoundField DataField="Item_UnitofIssue" HeaderText="Unit of Issue" SortExpression="Item_UnitofIssue" />
                            <asp:BoundField DataField="Item_Image" HeaderText="Image" SortExpression="Item_Image" />
                            <asp:BoundField DataField="Item_ItemNo" HeaderText="Item No" SortExpression="Item_ItemNo" />
                            <asp:BoundField DataField="Item_MaxOrderQty" HeaderText="Max Qty" SortExpression="Item_MaxOrderQty" />
                            <asp:TemplateField HeaderText="ID" Visible="False">
                                <ItemTemplate>
                                    <asp:Label ID="lblItemID" runat="server" Text='<%# Eval("Item_ID") %>'></asp:Label>
                                </ItemTemplate>
                            </asp:TemplateField>
                        </Columns>
                    </asp:GridView>
                </td>
                <td>
                    &nbsp;
                </td>
                <td valign="top">
                    <asp:GridView ID="ItemInOrder" runat="server" OnRowDeleting="ItemInOrder_RowDeleting"
                        EmptyDataText=".. no items in order">
                        <Columns>
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:Button ID="btnDelete" runat="server" Text="Del" CommandArgument='<%#DataBinder.Eval(Container,"DataItem.id")%>'
                                        OnClick="btnDelete_Click" />
                                </ItemTemplate>
                            </asp:TemplateField>
                        </Columns>
                    </asp:GridView>
                </td>
            </tr>
            <tr>
                <td valign="top">
                    &nbsp;
                </td>
                <td>
                    &nbsp;
                </td>
                <td valign="top">
                    &nbsp;
                </td>
            </tr>
        </table>
    </div>
    </form>
</body>
</html>

           
         

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Object reference not set to an instance of an object.

Asked by chris_desborough in Programming for ASP.NET, C# Programming Language

Tags: asp.net c#

About this solution