asked on

listview/linq - expand selection

Hi,
As a continuation of this thread:
https://www.experts-exchange.com/questions/24362259/listview-xml-linqdatasource-need-help-data-not-showing.html?anchorAnswerId=24258710#a24258710

The code works but how do I expand it to include other items.

so would like to include duration and prices.
<courseList filedUnder="Courses">
<category code="4wd" title="4wd Operation" >
<product code="lr" title="4wd Bush Driving">
<duration>1 Day</duration>
</product>
<product code="hr" title="4wd Defensive Driving">
<duration>1 Day</duration>
</product>
<product code="sr" title="Self-Recovery">
<duration>1 Day</duration>
</product>
</category>
</courseList>

Thanks
Tania

Protected Sub listsource_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.LinqDataSourceSelectEventArgs) Handles listsource.Selecting
		 
    Dim xd As XDocument = XDocument.Load(Server.MapPath("/App_Data/courseList.xml"))
    Dim list = (From x In xd.Descendants("product").Attributes("title") _
			Select New With {.Title = x.Value}).ToList() 
			 e.Result = list
 
End Sub
	 
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
 
End Sub

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Sreedhar Vengala

In C# its:

XDocument xd = XDocument.Load(@"c:\courseList.xml");
             var list = xd.Descendants("product").
                 Select(element => new
                                       {
                                           Title = element.Attribute("title").Value, 
                                           Duration = element.Element("duration").Value
                                       });
             e.Result = list;

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Member_2_4426104

ASKER

Hi,
Based on this:

https://www.experts-exchange.com/questions/24127127/Linq-C-to-VB-conversion-select-new.html?anchorAnswerId=23595294#a23595294

Have converted it as follows:
      Dim query = From q In xd...<product> _
Select New With { _
.title = q.Attribute("title").Value, _
.duration = q.Element("duration").Value _
}

             e.Result = query

Get this error:
System.NullReferenceException: Object reference not set to an instance of an object.

here:
Select New With { _

Tania

ASKER CERTIFIED SOLUTION

Sreedhar Vengala

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Member_2_4426104

ASKER

Hi,
Thanks.

Getting same error:

System.NullReferenceException: Object reference not set to an instance of an object.

Select New With {.Title = element.Attribute("title").Value, _

T

Sreedhar Vengala

Works fine for me => code as below
Can you show me your code

Protected Sub Page_Load (ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
        Dim xd As XDocument
        xd = XDocument.Load ("c:\courseList.xml")
        Dim list = From element In xd.Descendants("product") _
                Select New With {.Title = element.Attribute("title").Value, _
                .Duration = element.Element("duration").Value}
    End Sub

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Member_2_4426104

ASKER

Hi
Not using Page_Load.

Its tied to linqdatasource /listview:

Protected Sub listsource_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.LinqDataSourceSelectEventArgs) Handles listsource.Selecting

Dim xd As XDocument = XDocument.Load (Server.MapPath("/App_Data/courseList.xml"))
Dim list = From element In xd.Descendants("product") _
Select New With {.Title = element.Attribute("title").Value, _
.Duration = element.Element("duration").Value}
e.Result = list

End Sub

Member_2_4426104

ASKER

Forgot to add:

LinqDataSource.Selecting event

Sreedhar Vengala

so does that sorted you out ?

Member_2_4426104

ASKER

no,

Protected Sub listsource_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.LinqDataSourceSelectEventArgs) Handles listsource.Selecting

Dim xd As XDocument = XDocument.Load (Server.MapPath("/App_Data/courseList.xml"))
Dim list = From element In xd.Descendants("product") _
Select New With {.Title = element.Attribute("title").Value, _
.Duration = element.Element("duration").Value}
e.Result = list

End Sub

with the above get:

System.NullReferenceException: Object reference not set to an instance of an object.

Sreedhar Vengala

Works for me: <Code Produced below>

<%@ Page Language="vb" AutoEventWireup="false" CodeBehind="Default.aspx.vb" Inherits="WebApplication2._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>
</head>
<body>
 
    <form id="form1" runat="server">
    <div>
    
    </div>
    <script runat = server>
        Protected Sub listsource_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.LinqDataSourceSelectEventArgs) Handles listSource.Selecting
            Dim xd As XDocument = XDocument.Load("c:\courseList.xml")
            Dim list = From element In xd.Descendants("product") _
                    Select New With {.Title = element.Attribute("title").Value, _
                    .Duration = element.Element("duration").Value}
            e.Result = list
        End Sub
    </script>
    <asp:LinqDataSource 
      		ID="listSource" 
      		runat="server" 
      		OnSelecting="listsource_Selecting" 
      		 />
 
    <asp:ListView ID="ListView1" runat="server" DataSourceID = "listsource">
      <LayoutTemplate>
            <div id="datatable">
              <table id="Table1" border="1" class="prodtbl" runat="server">
                <tr class="mainheader">
                  <th > <asp:LinkButton ID="btnSortName" 
                       runat="server" CommandName="Sort" 
                       CommandArgument="title" Text="Course" />
                  </th>
                  <th> <asp:LinkButton ID="btnSortDuration" 
                     runat="server" CommandName="Sort" 
                     CommandArgument="title" Text="Duration" />
                  </th>
                  <th> <asp:LinkButton ID="btnSortDate" 
                      runat="server" CommandName="Sort" 
                      CommandArgument="title" Text="Date" />
                  </th>
                </tr>
                <tr id="itemPlaceholder" runat="server" /></tr>
              </table>
              <div class="pager">
                <asp:DataPager ID="pagerTop" runat="server" PageSize="20">
                  <Fields>
                    <asp:NextPreviousPagerField 
                         ButtonCssClass="command" 
                         FirstPageText="&laquo;" PreviousPageText="&lsaquo;" 
                         RenderDisabledButtonsAsLabels="true" 
                         ShowFirstPageButton="true" ShowPreviousPageButton="true" 
                         ShowLastPageButton="false" ShowNextPageButton="false"
                                            />
                    <asp:NumericPagerField
                         ButtonCount="5" NumericButtonCssClass="command" 
                         CurrentPageLabelCssClass="current" NextPreviousButtonCssClass="command"
                                            />
                    <asp:NextPreviousPagerField 
                         ButtonCssClass="command" 
                         LastPageText="&raquo;" NextPageText="&rsaquo;" 
                         RenderDisabledButtonsAsLabels="true" 
                         ShowFirstPageButton="false" ShowPreviousPageButton="false" 
                         ShowLastPageButton="true" ShowNextPageButton="true"
                                            />
                  </Fields>
                </asp:DataPager>
              </div>
            </div>
          </LayoutTemplate>
          <ItemTemplate>
            <tr id="row" >
               <td><%# Eval("title") %></td>
               <td><%# Eval("duration") %></td> 
              <td><%# Eval("title") %></td>
            </tr>
          </ItemTemplate>
 
    </asp:ListView>
    </form>
</body>
</html>

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Sreedhar Vengala

Also can you show me you xml (if different produced in this thread)

Member_2_4426104

ASKER

Hi,
something else must be going on - i get the same error:

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

Line 17: Dim xd As XDocument = XDocument.Load(Server.MapPath("/App_Data/courseList.xml"))
Line 18: Dim list = From element In xd.Descendants("product") _
Line 19: Select New With {.Title = element.Attribute("title").Value, _
Line 20: .Duration = element.Element("duration").Value}
Line 21: e.Result = list

Source File: c:\websites\125344vg9\training\test\test2.aspx Line: 19

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
ASP.training_test_test2_aspx._Lambda$__1(XElement element) in c:\websites\125344vg9\training\test\test2.aspx:19
System.Linq.<SelectIterator>d__d`2.MoveNext() +185
System.Linq.Enumerable.Count(IEnumerable`1 source) +202
lambda_method(ExecutionScope ) +48
System.Linq.EnumerableExecutor`1.Execute() +155
System.Linq.EnumerableExecutor`1.ExecuteBoxed() +23
System.Linq.EnumerableQuery`1.System.Linq.IQueryProvider.Execute(Expression expression) +75
System.Web.Query.Dynamic.DynamicQueryable.Count(IQueryable source) +139
System.Web.UI.WebControls.DynamicQueryableWrapper.Count(IQueryable source) +6
System.Web.UI.WebControls.LinqDataSourceView.ExecuteSelectAutoSortAndPage(IQueryable source, DataSourceSelectArguments arguments) +127
System.Web.UI.WebControls.LinqDataSourceView.ExecuteSelectQuery(LinqDataSourceSelectEventArgs selectEventArgs, Object selectResult, Object table, Boolean storeOriginalValues) +308
System.Web.UI.WebControls.LinqDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments) +482
System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) +17
System.Web.UI.WebControls.DataBoundControl.PerformSelect() +149
System.Web.UI.WebControls.ListView.PerformSelect() +56
System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +70
System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +82
System.Web.UI.WebControls.ListView.CreateChildControls() +53
System.Web.UI.Control.EnsureChildControls() +87
System.Web.UI.Control.PreRenderRecursiveInternal() +50
System.Web.UI.Control.PreRenderRecursiveInternal() +170
System.Web.UI.Control.PreRenderRecursiveInternal() +170
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2041

<%@ Page Language="vb" AutoEventWireup="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>
</head>
<body>
 
    <form id="form1" runat="server">
    <div>
    
    </div>
    <script runat = server>
        Protected Sub listsource_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.LinqDataSourceSelectEventArgs) Handles listSource.Selecting
            Dim xd As XDocument = XDocument.Parse("<courseList filedUnder='Courses'>" & _
          "<category code='4wd' title='4wd Operation' >" & _
            "<product code='lr' title='4wd Bush Driving'>" & _
              "<duration>1 Day</duration>" & _
            "</product>" & _
            "<product code='hr' title='4wd Defensive Driving'>" & _
              "<duration>1 Day</duration>" & _
            "</product>" & _
            "<product code='sr' title='Self-Recovery'>" & _
              "<duration>1 Day</duration>" & _
            "</product>" & _
          "</category>" & _
        "</courseList>")
 
 
            Dim list = From element In xd.Descendants("product") _
                    Select New With {.Title = element.Attribute("title").Value, _
                    .Duration = element.Element("duration").Value}
            e.Result = list
        End Sub
    </script>
    <asp:LinqDataSource 
                ID="listSource" 
                runat="server" 
                OnSelecting="listsource_Selecting" 
                 />
 
    <asp:ListView ID="ListView1" runat="server" DataSourceID = "listsource">
      <LayoutTemplate>
            <div id="datatable">
              <table id="Table1" border="1" class="prodtbl" runat="server">
                <tr class="mainheader">
                  <th > <asp:LinkButton ID="btnSortName" 
                       runat="server" CommandName="Sort" 
                       CommandArgument="title" Text="Course" />
                  </th>
                  <th> <asp:LinkButton ID="btnSortDuration" 
                     runat="server" CommandName="Sort" 
                     CommandArgument="title" Text="Duration" />
                  </th>
                  <th> <asp:LinkButton ID="btnSortDate" 
                      runat="server" CommandName="Sort" 
                      CommandArgument="title" Text="Date" />
                  </th>
                </tr>
                <tr id="itemPlaceholder" runat="server" /></tr>
              </table>
              <div class="pager">
                <asp:DataPager ID="pagerTop" runat="server" PageSize="20">
                  <Fields>
                    <asp:NextPreviousPagerField 
                         ButtonCssClass="command" 
                         FirstPageText="&laquo;" PreviousPageText="&lsaquo;" 
                         RenderDisabledButtonsAsLabels="true" 
                         ShowFirstPageButton="true" ShowPreviousPageButton="true" 
                         ShowLastPageButton="false" ShowNextPageButton="false"
                                            />
                    <asp:NumericPagerField
                         ButtonCount="5" NumericButtonCssClass="command" 
                         CurrentPageLabelCssClass="current" NextPreviousButtonCssClass="command"
                                            />
                    <asp:NextPreviousPagerField 
                         ButtonCssClass="command" 
                         LastPageText="&raquo;" NextPageText="&rsaquo;" 
                         RenderDisabledButtonsAsLabels="true" 
                         ShowFirstPageButton="false" ShowPreviousPageButton="false" 
                         ShowLastPageButton="true" ShowNextPageButton="true"
                                            />
                  </Fields>
                </asp:DataPager>
              </div>
            </div>
          </LayoutTemplate>
          <ItemTemplate>
            <tr id="row" >
               <td><%# Eval("title") %></td>
               <td><%# Eval("duration") %></td> 
              <td><%# Eval("title") %></td>
            </tr>
          </ItemTemplate>
 
    </asp:ListView>
    </form>
</body>
</html>

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Member_2_4426104

ASKER

aaaahhhhhhhhhh - the agony of it!

it was the viewstate:

EnableViewState=true

All works just fine.

T

Sreedhar Vengala

cool.