title: Microsoft Owin Security - Claims Constructor Value cannot be null
body: <p>I am a bit new to Owin security. I have a legacy application with a user table and a specific role defined in it for each user.</p>
  
  <p>I am trying to implement a custom user manager and user store to look at that table and authorize users for my MVC application using the OOTB [Authorize(Roles = "Contributor")] attributes.</p>
  
  <p>I had a piece of code working that did this in a very basic way using the standard Account controller with the customer user store below.</p>
  
  <p>My problem is that the GetRolesAsync either isn't firing anymore or its getting an exception before it gets there from the Claims constructor:</p>
  
  <p>Parameter name: </p>
  
  <pre><code>value
     at System.Security.Claims.Claim..ctor(String type, String value, String valueType, String issuer, String originalIssuer, ClaimsIdentity subject, String propertyKey, String propertyValue)
     at System.Security.Claims.Claim..ctor(String type, String value, String valueType)
     at Microsoft.AspNet.Identity.ClaimsIdentityFactory`1.&lt;CreateAsync&gt;d__0.MoveNext()
  </code></pre>
  
  <p><strong>Any ideas why I would suddenly be seeing this exception since I am not really interested in Claims for the identity. Has there been some change in my examples thats working that has moved this from Roles based to Claims based security?</strong></p>