SPDataSource to show GridView of BCS external list

I am using an SPDataSource and an ASP GridView to attempt to display a grid of external list data. While I have been successful targeting a normal SharePoint list, when I attempt to target an external list I run into problems. I am using SPDataSource to pull in a CAML query using the SelectCommand, but get errors such as:

1. File not found
2. List 'abc123' does not exist at site with URL 'http://abcdev'
3. Object not set to the instance of an object

Here is my code for SPDataSource:

 Scope='Recursive'> Name='clientname' Ascending='true' />">
    
         Name="ListName" DefaultValue="GUID for external list" />
         Name="WebURL" DefaultValue="{rootsitecollection}" />
    

The external list I am targeting is returned from the top-level web of the site collection "http://abcdev". So, what am I doing wrong that I cannot get the external list to display in my grid?

I believe the issue with my code falls on the SPDataSource Parameter ...

 Name="WebURL" DefaultValue="{rootsitecollection}" />

but what am I doing wrong?



I have tried the following DefaultValues:

1. {rootsitecollection}

2. ""  -[leaving it blank]

3. /

4. http://abcdev

5. abcdev



Unfortunately, all return one of the errors posted above. Any suggestions on a fix?

Thank you so much in advance.