asp:hyperlink in repeater visibility

spinout · February 27th, 2008, 12:41 AM

Hello,

I have an ASP:repeater object in my page and I'm trying to control the visiblity of an ASP:hyperlink object within the repeater based on whether the specific record which is returned has a website link or not.

Obviously if the database record contains a website link then I want the repeater to display the hyperlink. If it doesn't then I do not want the repeater to display it. Any suggestions?

Imar · February 27th, 2008, 03:29 AM

Hi there,

There are a few ways to do this. First of all, you could embed an expression in the Visible property that checks whether the string is empty:

Code:

<asp:HyperLink runat="server" NavigateUrl='<%# Eval("Url") %>' 
    Visible='<%# Not System.String.IsNullOrEmpty(Eval("Url")) %>'>
  Go to web site
</asp:HyperLink>

This code checks if the Url field contains a hyper link. If not, the entire HyperLink is hidden.

Alternatively, you could hook into the ItemCreated (or ItemDataBound) event of the Repeater, find the HyperLink, look at e.DataItem (that represents the data you are binding ) and then determine its visibility. For example, when binding to a Company object that has a Url property you could do something like this:

Code:

Protected Sub Repeater1_ItemCreated(ByVal sender As Object, _
    ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs) _ 
    Handles Repeater1.ItemCreated
  Select Case e.Item.ItemType
    Case ListItemType.AlternatingItem, ListItemType.Item
      Dim myCompany As Company = CType(e.Item.DataItem, Company)
      ' No need to CType to a HyperLink because Control has the 
      ' Visible property
      Dim myLink As Control = e.Item.FindControl("hyperUrl")
      myLink.Visible = Not String.IsNullOrEmpty(myCompany.Url)
  End Select
End Sub

This code uses FindControl to locate the HyperLink and then sets its visibility.

If your data is different (e.g. you're binding to a DataSet) you need a different cast (CType), probably into a DataRowView.

Hope this helps,

Imar
---------------------------------------
Imar Spaanjaars
http://Imar.Spaanjaars.Com
Everyone is unique, except for me.
Author of Beginning ASP.NET 3.5 : in C# and VB, ASP.NET 2.0 Instant Results and Dreamweaver MX 2004
Want to be my colleague? Then check out this post.

spinout · February 27th, 2008, 03:52 AM

Hi Imar,

I tried what you suggested, but something isn't quite right. This is what I have as my page code.

Code:

<asp:Hyperlink NavigateUrl="video.aspx?id=<%# DataBinder.Eval(Container.DataItem, "iVideoId") %>"
Text="Watch video" Visible='<%# Not System.String.IsNullOrEmpty(Eval("iVideoId")) %>'></asp:Hyperlink>

Strange thing is, when I added the part that you suggested to the 'Visible' parameter I only got 1 of my 6 repeater records returned and the link actually isn't invisible.

Imar · February 27th, 2008, 04:06 AM

Do you have other data in your Repeater as well? Or just the hyperlink? To make it easier to see what happens, try adding another control to the ItemTemplate like a Label.

And what does iVideoId contain? Do you know what data it contains exactly for the records you are displaying?

And this doesn't look right either:

Code:

NavigateUrl="video.aspx?id=<%# DataBinder.Eval(Container.DataItem, "iVideoId") %>"

Shouldn't that be:

Code:

NavigateUrl='<%# "video.aspx?id=" & DataBinder.Eval(Container.DataItem, "iVideoId") %>'

Finally, can you add a few line breaks here and there when you post code here at P2P? The page is about 6 feet wide now.... ;)

Imar
---------------------------------------
Imar Spaanjaars
http://Imar.Spaanjaars.Com
Everyone is unique, except for me.
Author of Beginning ASP.NET 3.5 : in C# and VB, ASP.NET 2.0 Instant Results and Dreamweaver MX 2004
Want to be my colleague? Then check out this post.

spinout · February 27th, 2008, 04:17 AM

Yes, there are about 6 different instances of <%# DataBinder.Eval(Container.DataItem, "someField") %> in my repeater.

The 'iVideoId' should contain an integer value, being the id to pass to my video player to roll a specific video. At this stage all iVideoId's in my database are null because I want to test that at this stage the hyperlink should not be displaying for any of the records without a video ID.

(Sorry about the code, I usually do insert line breaks for that reason, but I forgot).

Imar · February 27th, 2008, 04:36 AM

In that case, you may need to compare against DBNull.Value, the database counterpart of null / Nothing:

Visible='<%# Eval("Url") IsNot DBNull.Value %>'

It's probably better to go the ItemCreated route as it gives you more flexibility and better control over the data you are testing.

Imar
---------------------------------------
Imar Spaanjaars
http://Imar.Spaanjaars.Com
Everyone is unique, except for me.
Author of Beginning ASP.NET 3.5 : in C# and VB, ASP.NET 2.0 Instant Results and Dreamweaver MX 2004
Want to be my colleague? Then check out this post.

spinout · February 27th, 2008, 05:40 AM

Thanks Imar, that seems to have sorted out my link visibility problems, however the code now does not appear to be populating the querystring of my NavigateUrl.

Code:

<asp:Hyperlink runat="server" NavigateUrl='video.aspx?id=<%# Eval("iVideoId") %>'
Text='Watch video' Visible='<%# Eval("iVideoId") IsNot DBNull.Value %>'></asp:Hyperlink>

What's happening is that navigate URL location is actually being set to "video.aspx?id=<%# Eval("iVideoId") %>" rather than "video.aspx?id=1234" when the page renders in the browser.

Imar · February 27th, 2008, 05:46 AM

Take a look at my second reply. The entire expression, including the string literal video.aspx?id= should be part of the data binding expression enclosed in '<%# %>'

Imar
---------------------------------------
Imar Spaanjaars
http://Imar.Spaanjaars.Com
Everyone is unique, except for me.
Author of Beginning ASP.NET 3.5 : in C# and VB, ASP.NET 2.0 Instant Results and Dreamweaver MX 2004
Want to be my colleague? Then check out this post.

spinout · February 27th, 2008, 06:06 AM

Oops, I missed part of what you were saying in your second reply. I noticed you had changed my double quotes to single quotes, but I didn't pick up that you had made the string literal a part of the expression. It's working now!!

Just one problem I've noticed, the link is now invisible when iVideoId is Null, except the <li> bullet next to the link is still always visible which looks a little bit strange if the hyperlink is invisible. Is there a way to instruct <li id="video"> to be invisible when the link is invisible?

Here is my full code

Code:

<div id="Link">[list]
<li id="video">
<asp:Hyperlink runat="server" 
NavigateUrl='<%# "video.aspx?id=" & DataBinder.Eval(Container.DataItem, "iVideoId") %>' 
Text='Watch video' Visible='<%# Eval("iVideoId") IsNot DBNull.Value %>'></asp:Hyperlink>
</li>
</ul>
</div>

Imar · February 27th, 2008, 06:11 AM

Yes, there is a way. Simply make the <li> runat='server", and move your code that determines visibility to the <li>:

Code:

<li id="video" runat="server" Visible='<%# Eval("iVideoId") IsNot DBNull.Value %>'>

BTW, shouldn't the[list] be located in a different template like the HeaderTemplate?

Imar
---------------------------------------
Imar Spaanjaars
http://Imar.Spaanjaars.Com
Everyone is unique, except for me.
Author of Beginning ASP.NET 3.5 : in C# and VB, ASP.NET 2.0 Instant Results and Dreamweaver MX 2004
Want to be my colleague? Then check out this post.