Totally lost – data binding expressions inside GridView’s template - asp.net

1) On aspx page we define GridView control named gvwPolls, and inside its template we define a user control named pollBox1
<asp:GridView ID="GridView1" DataSourceID="objPolls" ...>
<Columns>
<asp:TemplateField>
<ItemTemplate>
Question is : <%# Eval("QuestionText") %> <br />
<mb:PollBox ID="PollBox1" runat="server" PollID='<%# Eval("ID") %>' />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<asp:ObjectDataSource ID="objPolls" ...></asp:ObjectDataSource>
a) I assume that inside gvwPolls’s template, the gvwPollBox1.DataBind is called before PollID='<%# Eval("ID") %>' and <%# Eval("QuestionText") %> expressions get evaluated?!
b) Can someone offer some explanation how or why is gvwPollBox1.DataBind called before PollID='<%# Eval("ID") %>' and <%# Eval("QuestionText") %> expressions get evaluated?
2) Continuing with the above example:
-- pollBox1 user control defines a Repeater control named rptOptions:
<asp:Repeater runat="server" ID="rptOptions">
<ItemTemplate>
<%# Eval("pollBoxTitle") %>
</ItemTemplate>
</asp:Repeater>
-- In pollBox1’s code-behind file we bind rptOptions to a data source inside DoBinding() method.
-- We also override pollBox1’s DataBind() method:
public override void DataBind()
{
base.DataBind();
DoBinding();
}
a) I assume that due to overriding pollBox1.DataBind(), the data binding expression <%# Eval("pollBoxTitle") %> ( defined inside rptOptions’s template ) will get evaluated prior to a call to DoBinding method? If so, won’t then <%# Eval("pollBoxTitle") %> get evaluated before rptOptions is actually bound to a data source?
b) If that is the case, how then is rptOptions able to extract value ( from data source’s pollBoxtitle property) from a data source, if at the time the <%# Eval("pollBoxTitle") %>
expression got evaluated, rptOptions wasn’t yet bound to any data source?
thanx

I can't explain why the page life cycle is the way that is, probably has something to do with rendering childs before the parent object. When exactly do you call .DataBind() in the PollBox control? Try to move it into an event that is later in the life cycle, like PreRender.
There is also another way to ensure it is working the way you want to:
Subscribe to the RowDataBound Event, use .FindControl("YourPollBoxID") to get the instance of the control current bound row, set the properties and perform a manuall .DataBind();

Related

Using c# in Web Forms to passing parameter to user control

From an aspx page, I am trying to display a user control for each item in a collection, but the C# seems to be ignored when tryign to set the UserControl parameter:
<%foreach (Fetus item in this.pregnancy.Fetus) {%>
//this returns a GUID:
"<%= item.Id.ToString() %>"
//this does not work, returns the characters between "" like < %= item.Id.ToString()%>:
<uc1:AntepartumCTGChart runat="server" ID="AntepartumCTGChart" FetusId="<%= item.Id.ToString()%>" />
<% } %>
I would expect this to work, what's wrong?
You have to use a data binding expression
<uc1:AntepartumCTGChart runat="server" ID="AntepartumCTGChart" FetusId='<%# item.Id.ToString()%>' />
But you have to call DataBind() in code behind for that to work.
You can also use a Repeater
<asp:Repeater ID="Repeater1" runat="server">
<ItemTemplate>
<uc1:AntepartumCTGChart runat="server" ID="AntepartumCTGChart" FetusId='<%# Eval("id").ToString()%>' />
</ItemTemplate>
</asp:Repeater>
And then bind data to it in code behind
Repeater1.DataSource = pregnancy.Fetus;
Repeater1.DataBind();

How to get parent datasource Eval() inside a nested Repeater? [duplicate]

This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
Accessing parent data in nested repeater, in the HeaderTemplate
I have a nested repeater being databound... let's say the top level repeater is an OrderRow and the inner repeaters are bound to LineItem rows from my DB. ASPX is something like this:
<asp:Repeater ID="rptOrder" runat="server">
<ItemTemplate>
<%# Eval("OrderID") %>:<br/>
<asp:Repeater ID="rptLineItems" runat="server">
<ItemTemplate>
<%# Eval("SomeColumn1"); %>
<%# Eval("SomeColumn2"); %>
<%# Eval("SomeColumn3"); %>
</ItemTemplate>
<FooterTemplate>
<asp:Button ID="btnAddLine" runat="server" CommandArgument=<%# ???? %> />
</FooterTemplate>
</asp:Repeater>
</ItemTemplate
</asp:Repeater>
Now the button on the inner footer will be used to add a new line item... but the command argument needs to be the OrderID from the outer repeater, so we know which order to add to. Obviously a regular Eval() call won't work here, because it will have the inner repeater's DataRowView as a source [actually, it won't, since it's in the footer]. How do I get this value? Am I going to have to set this dynamically in the ItemDataBound event of the outside repeater?
Since the call are serial you can use the code behind to save the last order id and use it later.
Here is the idea.
<asp:Repeater ID="rptOrder" runat="server">
<ItemTemplate>
<%#GetOrderID(Container.DataItem)%><br />
<asp:Repeater ID="rptLineItems" runat="server">
<ItemTemplate>
<%# Eval("SomeColumn1"); %>
<%# Eval("SomeColumn2"); %>
<%# Eval("SomeColumn3"); %>
</ItemTemplate>
<FooterTemplate>
<asp:Button ID="btnAddLine" runat="server" CommandArgument=<%=cLastOrderID%> />
</FooterTemplate>
</asp:Repeater>
</ItemTemplate
</asp:Repeater>
and on call behind
public int cLastOrderID = -1;
protected string GetOrderID(object oItem)
{
cLastOrderID = (int)DataBinder.Eval(oItem, "OrderID");
return cLastOrderID.ToString();
}
What I do here is that I call the GetOrderID to return the OrderID and I save it in a global value, and then later in the footer I use this global value. Hope this helps you.

asp.net repeater with usercontrol - setting commandargument

I have the following repeater code:
<asp:Repeater ID="repMain" runat="server" OnItemCommand="repMain_ItemCommand" EnableViewState="false">
<ItemTemplate>
<dmg:testcontrol runat="server" MyData=<%#Container.DataItem %>>
</dmg:testcontrol>
</ItemTemplate>
</asp:Repeater>
The testcontrol usercontrol looks like:
<%# Control Language="C#" AutoEventWireup="true" CodeBehind="TestControl.ascx.cs" Inherits="TestRepeater.TestControl" %>
<asp:Literal runat="server" ID="litMain" Text="<%#MyData.MyValue %>"></asp:Literal>
<asp:DropDownList runat="server" ID="dropdownMain"></asp:DropDownList>
<asp:Button runat="server" ID="btnMain" Text="Click Me" CommandName="Update" CommandArgument="<%#dropdownMain.SelectedValue%>"/>
Is it possible for me to send through the dropdownMain.SelectedValue as the CommandArgument?
Just now it is an empty string.
Thanks
Duncan
PS This is related to ASP.NET Repeater not binding after ItemCommand but I thought the two sufficiently different to keep apart.
A bit old question but I just my self found the answer to this one.
CommandArgument="<%#dropdownMain.SelectedValue%>"
Needs to look like this instead with single quotes! All inline codes within a asp.net controls have to be done this way instead.
CommandArgument='<%#dropdownMain.SelectedValue%>'
Why not get the selected value, and use it inside the Command function ?
(why to try to send it as argument, from the moment you can get it inside the command called function and its the same)

nested repeater pass value in header template

I have a nested repeater and i want to pass value in its header. Here is my code so far..
The main problem is the id of the control in header template is also coming from code behind.
<asp:Repeater ID="RptrProgCategory" runat="server">
<ItemTemplate>
<asp:Repeater ID="RptrPrograms" runat="server">
<HeaderTemplate><input type="hidden" id="<%= questvalue%>"/></HeaderTemplate>
<ItemTemplate>
<%# DataBinder.Eval(Container.DataItem, "cat") %>
</ItemTemplate>
</asp:Repeater>
</ItemTemplate>
</asp:Repeater>
I want value in questvalue from code behind. Any idea how to achieve this?
Edit: I wanted to put this value in a DataTable and bind that value in Repeater bcoz i want output like this may be <%# DataBinder.Eval(Container.DataItem, "questvalue") %> instead of <%= questvalue%>..but in tht case i am not able to find the control
Category1(id of hidden field )
subcat1
subcat2
subcat3
Category2(id of hidden field)
subcat4
subcat5..and so on..
Repeater mainRepeater = this.Page.FindControl("RptrProgCategory") as Repeater;
Repeater nestedRepeater = mainRepeater.FindControl("RptrProgCategory") as Repeater;
You can then do a FindControl in nestedRepeater for questValue.
Add a runat='server' to questvalue so that you can access it in code behind.
I am writing this from memory, syntax might not be correct but it should get you off in the right direction.
set the id of the control in the repeater to something like mycontrolId - and then on OnItemDataBound - (or even OnItemCreated) use findcontrol("mycontrolId") - and then change the id of the control to your questvalue param.

Unable to bind in asp.net grid Template Column

I am having trouble accessing the data field. I receive the error: Databinding methods such as Eval(), XPath(), and Bind() can only be used in the context of a databound control.
I can get the value but using <%# getOpenJobs((string)Eval("ParentPart")) %> but I need to use it in the if to display a certian picture if it passes the condition. Is there a better way to do this or am i just missing something simple?
<telerik:GridTemplateColumn UniqueName="hasOpenJobs" HeaderText="">
<ItemTemplate>
<% if (getOpenJobs((string)Eval("ParentPart")) > 1)
{ %>
<img src="../images/job-icon.gif" alt="Open Jobs" />
<%} %>
</ItemTemplate>
</telerik:GridTemplateColumn>
In these cases, I usually create a method in the code-behind to send back the final generated HTML. E.g.
<ItemTemplate>
<%# GetJobImageHtml((string)Eval("ParentPart")) %>
</ItemTemplate>
Then do whatever logic you need in the GetJobImageHtml() method and return a HTML string.

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