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The name 'tempDT' does not exist in the current context

chris_desborough
on
Medium Priority
616 Views
Last Modified: 2012-05-07
In the GridView1_SelectedIndexChanged method I'm getting 3 build errors saying that the name 'tempDT' does not exist.  Unable to fathom the reason for this, please advise.
PAGE CODE
==========
<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>
 
<!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
        {
            width: 100%;
        }
        .style2
        {
            width: 549px;
        }
    </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>
        <br />
        <table align="left" class="style1" cellspacing="15">
            <tr>
                <td bgcolor="#CCFF33" class="style2">
                    <asp:DropDownList ID="ddlCategory" runat="server" AutoPostBack="True" 
                        DataSourceID="SqlCategoriesList" DataTextField="Category" 
                        DataValueField="Category">
                    </asp:DropDownList>
                    - Select a category</td>
                <td bgcolor="#CCFF33">
                    Your order</td>
            </tr>
            <tr>
                <td class="style2">
                    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" 
                        DataKeyNames="Item_ID" DataSourceID="SqlItemList" 
                        EmptyDataText=".. Select a 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 valign="top">
                    <asp:GridView ID="ItemsInOrder" runat="server" 
                        EmptyDataText=".. No items in order">
                    </asp:GridView>
                    </td>
            </tr>
            <tr>
                <td class="style2">
                    <asp:Label ID="Label1" runat="server" Text=""></asp:Label><br />
                    <asp:Label ID="Label2" runat="server" Text=""></asp:Label><br />
                    <asp:Label ID="Label3" runat="server" Text=""></asp:Label><br />
                    <asp:Label ID="Label4" runat="server" Text=""></asp:Label><br />
                    <asp:Label ID="Label5" runat="server" Text=""></asp:Label><br />
                    <asp:Label ID="Label6" runat="server" Text=""></asp:Label><br />
                    <asp:Label ID="Label7" runat="server" Text=""></asp:Label><br />
                    <asp:Label ID="Label8" runat="server" Text=""></asp:Label>
                    <br />
                    <asp:Label ID="Label9" runat="server" Text=""></asp:Label> <br />
                    <asp:Label ID="Label10" runat="server" Text=""></asp:Label>
                    <br />
                </td>
                <td valign="top">
                    &nbsp;</td>
            </tr>
        </table>
    
    </div>
    </form>
</body>
</html>
 
CODE BEHIND
============
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
 
 
public partial class _Default : System.Web.UI.Page
{
 
 
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            CreateDataTable();
 
        }
    }
 
 
    private DataTable CreateDataTable()
    {
        DataTable tempDT = new DataTable();
 
        DataColumn myDataColumn;
 
        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "id";
        tempDT.Columns.Add(myDataColumn);
 
        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "qtyordered";
        tempDT.Columns.Add(myDataColumn);
 
        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "itemdesc";
        tempDT.Columns.Add(myDataColumn);
 
        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "unitofissue";
        tempDT.Columns.Add(myDataColumn);
 
        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "itemno";
        tempDT.Columns.Add(myDataColumn);
 
        return tempDT;
    }
 
    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;
        
        // Display selected item back to the page
        Label1.Text = "Cell 0 = " + row.Cells[0].Text;
        Label2.Text = "Cell 1 = " + row.Cells[1].Text;
        Label3.Text = "Cell 2 = " + row.Cells[2].Text;
        Label4.Text = "Cell 3 = " + row.Cells[3].Text;
        Label5.Text = "Cell 4 = " + row.Cells[4].Text;
        Label6.Text = "Cell 5 = " + row.Cells[5].Text;
        Label7.Text = "Cell 6 = " + row.Cells[6].Text;
        Label8.Text = "Cell 7 = " + row.Cells[7].Text;
        Label9.Text = "Record ID = " + idText;
        Label10.Text = "Qty Ordered ID = " + qtyText;
 
        
        // Insert data into the temp datatable
        DataRow myNewRow;
        myNewRow = tempDT.NewRow();
 
        myNewRow["id"] = idText;
        myNewRow["qtyordered"] = qtyText;
        myNewRow["itemdesc"] = row.Cells[2].Text;
        myNewRow["unitofissue"] = row.Cells[3].Text;
        myNewRow["itemno"] = row.Cells[5].Text;
 
        tempDT.Rows.Add(myNewRow);
 
        // Bind the grid with the temp datatable
        ItemsInOrder.DataSource = tempDT;
        ItemsInOrder.DataBind();
 
    }
 
    protected void GridView1_SelectedIndexChanging(Object sender, GridViewSelectEventArgs e)
    {
        GridViewRow row = GridView1.Rows[e.NewSelectedIndex];
 
    }
 
    protected void SqlItemList_Selecting(object sender, SqlDataSourceSelectingEventArgs e)
    {
 
    }
}

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Commented:
As far as I can see the tempDT is private to the CreateDataTable method and would not exist in the GridView1_SelectedIndexChanged subroutine as it is not being called.

Author

Commented:
Okay... fairly new to C#. How would you suggest I correct the problem?
Top Expert 2013

Commented:
Just part of your code with some modifications:
Just making tempDT accessible to entire class...
public partial class _Default : System.Web.UI.Page
{
      DataTable tempDT = null;
 
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            CreateDataTable();
         }
    }
 
 
    private DataTable CreateDataTable()
    {
        tempDT = new DataTable();
 
        DataColumn myDataColumn;
 
...Rest of code remains as it is...

Author

Commented:
Now getting an another error in the GridView1_SelectedIndexChanged method on this line:

 myNewRow = tempDT.NewRow(); - Object reference not set to an instance of an object.





Top Expert 2013
Commented:
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Commented:
Hi ,

As you said you are new to C# . As you are using ASP.net so each time you click ne request is processed. In order to keep track of older data you have to use state management of ASP.net.

Session.
ViewState.

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            CreateDataTable();

        }
    }


    private DataTable CreateDataTable()
    {
        DataTable tempDT = new DataTable();

        DataColumn myDataColumn;

        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "id";
        tempDT.Columns.Add(myDataColumn);

        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "qtyordered";
        tempDT.Columns.Add(myDataColumn);

        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "itemdesc";
        tempDT.Columns.Add(myDataColumn);

        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "unitofissue";
        tempDT.Columns.Add(myDataColumn);

        myDataColumn = new DataColumn();
        myDataColumn.DataType = Type.GetType("System.String");
        myDataColumn.ColumnName = "itemno";
        tempDT.Columns.Add(myDataColumn);

        ViewState["Data"] = tempDT;

        return tempDT;
    }

    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;

        // Display selected item back to the page
        Label1.Text = "Cell 0 = " + row.Cells[0].Text;
        Label2.Text = "Cell 1 = " + row.Cells[1].Text;
        Label3.Text = "Cell 2 = " + row.Cells[2].Text;
        Label4.Text = "Cell 3 = " + row.Cells[3].Text;
        Label5.Text = "Cell 4 = " + row.Cells[4].Text;
        Label6.Text = "Cell 5 = " + row.Cells[5].Text;
        Label7.Text = "Cell 6 = " + row.Cells[6].Text;
        Label8.Text = "Cell 7 = " + row.Cells[7].Text;
        Label9.Text = "Record ID = " + idText;
        Label10.Text = "Qty Ordered ID = " + qtyText;


        // Insert data into the temp datatable
        DataRow myNewRow;
        DataTable tempDT = (DataTable)ViewState["Data"];
        myNewRow = tempDT.NewRow();

        myNewRow["id"] = idText;
        myNewRow["qtyordered"] = qtyText;
        myNewRow["itemdesc"] = row.Cells[2].Text;
        myNewRow["unitofissue"] = row.Cells[3].Text;
        myNewRow["itemno"] = row.Cells[5].Text;

        tempDT.Rows.Add(myNewRow);
        ViewState["Data"] = tempDT;
        // Bind the grid with the temp datatable
        ItemsInOrder.DataSource = tempDT;
        ItemsInOrder.DataBind();

    }

    protected void GridView1_SelectedIndexChanging(Object sender, GridViewSelectEventArgs e)
    {
        GridViewRow row = GridView1.Rows[e.NewSelectedIndex];

    }

    protected void SqlItemList_Selecting(object sender, SqlDataSourceSelectingEventArgs e)
    {

    }


Author

Commented:
Thanks sami, now working as expected. Setting it 'static' made the difference. Thanks to other contributors for their advice.
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