Dynamic charts at runtime in SSRS

You cannot. Check this forum posting which has a reponse from Microsoft.

Yes, it was an active decision that the 2008 design evironments would not support continuous backwards compatability but would rather be a one way upgrade. This was not a casual decision and it is understood how it can be an impact.

You can read the entire posting for more details on why you are unable to use VS2008 for SSRS 2005 projects. Very annoying, but I guess I can understand why they had to make that decision. Just about the only reason I have VS2005 on my dev machine now is for Reporting Services projects since our company is not going to be upgrading to SQL Server 2008 anytime soon.

This is, honestly, a guess as I don't have SQL 2008 Express to test this on - but it definitely works on SQL 2005 standard.

I think you can configure the property using rs.exe

Create a text file (I'm assuming you'll call it myReportsEnable.rss) and add the following text to it:

Public Overridable Sub Main()
    SetSystemProperties
End Sub

Private Sub SetSystemProperties()

    Dim Properties(0) As Microsoft.SqlServer.ReportingServices2008.[Property]
    Properties(0) = New Microsoft.SqlServer.ReportingServices2008.[Property]
    Properties(0).Name = "EnableMyReports"
    Properties(0).Value = "True"
    RS.SetSystemProperties(Properties)
End Sub

(I'm getting this from SQL2005, so I'm assuming that Microsoft.SqlServer.ReportingServices2008 is the right type to use - apologies if it's not)

Save the file, then execute it from a command line using rs.exe:

rs -i myReportsEnable.rss -s http://~YourServerName~/reportserver