Why can't I reference System.ComponentModel.DataAnnotations?

Question

I\'m trying to use DataAnnotations in my WPF project to specify a maximum length of strings, with the following:

using System.ComponentModel.DataAnnotations;         


        

Answer 1

System.ComponentModel.DataAnnotations is contained in its own assembly so you need to make sure you have it refernced. Just simply:

1). Right click on Soloution and choose add.

2). Choose reference from the list.

3). Search " System.ComponentModel.DataAnnotation " and tick the check box on its left hand side and press ok.

Job done, shouldnt have any refernce errors.

Answer 2

I upgraded from Silverlight 4 to Silverlight 5 and then I was having this issue. Although I had a reference to "System.ComponentModel.DataAnnotations" under "References" in my project, it had a yellow yield sign by it that indicated the previously referenced assembly could not be found. It turned out that the properties of the "System.ComponentModel.DataAnnotations" reference indicated "Specific Version = True", when I changed this to "Specific Version = False" it fixed the issue. Right click on the "System.ComponentModel.DataAnnotations" assembly under "References" and select "Properties" from the context menu. Check that the property value for "Specific Version = False".

It must have been referencing the old Silverlight 4 assembly which was no longer available after the upgrade to Silverlight 5.