Aggregation on asp:Treeview using xml datasource

I need to output distinct value of the DateTime element of the xml along with the number of time it occurs in the xml, all this using asp:treeview control.

xml file:

     <company>
         <Status>0</Status>
          <StatusDescription></StatusDescription>
           <FileList>
      <File>
        <FileID>120012</FileID>
        <DateTime>开发者_如何学Go;3/12/2011</DateTime>
      </File>
      <File>
        <FileID>120010</FileID>
        <DateTime>3/13/2011</DateTime>
      </File>
      <File>
        <FileID>120011</FileID>
        <DateTime>3/12/2011</DateTime>
      </File>
    </FileList>
</company>

output required:

3/12/2011 (2) 3/13/2011 (1)

I am able to bind and list the dates, but how do i make it display distinct values and also the count.

thanks, any help appreciated