title: unique column of type nvarchar
body: <p>I have a simple table: </p>
  
  <p><code>File</code>: <code>path | deleted | categories | description</code></p>
  
  <p>I want to use the table for a Linq to SQL entity model. On the model, that column <code>path</code> (which is string there, <code>nvarchar</code> in database) can be set as primary key, but this is not the case with the Visual Studio table designer.</p>
  
  <p>A path is what makes one file unique, so I have to make sure there are no duplicate paths in the table. How to achieve that ? Thanks for the time. </p>