If you’ve had this problem, then two things to make you feel better:
- The solution is very easy
- The cause of the problem is stupid stupid stupid. You can bang your head against the keyboard, there’s no way you could have known.
This post, meanders a bit, so if you want the solution, jump to the bottom.
Still here? Sucker.
So, what are the prerequisites to causing this problem:
- you have a dataview web part inserted into a master page;
- the dataview refers to data in a list; and
- the list is scoped at the root web of the site collection.
I think that’s it.
The web part will display correctly anywhere in your root web, but nowhere else. I’m calling it a “web” here because it maps to how Sharepoint’s API. If it helps for you to think about it as a single “Site” in WSS2.0 fashion, go nuts. When you visit subsites, you see the following error:
“Unable to display this Web Part. To troubleshoot the problem, open this Web page in a Windows SharePoint Services-compatible HTML editor such as Microsoft Office SharePoint Designer. If the problem persists, contact your Web server administrator.”
How helpful, especially if you’re an administrator or developer. As if they’d have a magic wand to fix the problem. The error might as well say:
“You’re screwed. Unless you’re a clever developer, give up, swear at Sharepoint and call tech support. Not many people at your company are going to be able to help you.”
Which is silly, because once we come to the cause, the error is completely within the realms of detection. To the developer who wrote that line of code… 10 minutes on the naughty step.
The problem is seemingly unresolveable. If you try to add the dataview directly to a page in a subsite, it works fine, but master page? Sharepoint tells you to go whistle.
The cause? Sharepoint doesn’t know which “web” the list comes from.
The Dataview web part can take parameters, including, parameters which tell pages where to find a list. In Sharepoint Designer, when you edit a master page, it fails to insert a parameter telling pages the list lives in the root.
Bad Sharepoint Designer! Bad!
The problem compounded because taking a dataview created on a subsite and dumping the code into the masterpage doesn’t work either (which makes it very tricky to solve).
To figure this out, I took the following steps in Sharepoint Designer:
- Created a dataview in the master page (worked at top level and nowhere else)
- Created the dataview with the exact same settings on a page in a subsite
- Copied the code snippets into a text-editor and compared them side-by-side
A side-by-side comparison revealed several things…
First, the datasource control (a child of the dataview web part) is referred to with a different namespace in the master page than in the page itself. This is why you can’t copy dataview code from a regular page into a master page. Maybe there’s a good reason for having done this, but I think the masterpage programmer forgot to speak to the regular page programmer. However, that isn’t the root cause, but something to be aware of.
Second, THERE’S ANOTHER PARAMETER. OMG!!! Froth, swear, stomp, swear, slam your keyboard. Feel better?
Knowing a parameter exists and knowing the syntax are two different things. Before finding the actual code, I was pretty confident the problem was down to subsites not knowing where the list was.
The worst thing is that the url of the web is actually part of the dataview web part, down at the very bottom of the code. Why doesn’t this flow through to the datasource? Naughty step!
It’s simple enough to copy the parameter from the subsite dataview into the masterpage dataview.
<WebPartPages:DataFormParameter Name=”WebURL” ParameterKey=”WebURL” PropertyName=”ParameterValues” DefaultValue=”/”/>
I don’t believe the approach is necessary if you’re referring to a list in a subsite (the parameter should be inserted automatically).
Hope that helps!