c# - Nullable object must have a value, Linq to SQL, MVC issues -

i've taken on project developer has left company , not overly familiar mvc. when running program error "nullable object must have value".

one of cells in table populated following:

<td>@sra_acquire.models.auth.users.getusernamebyid((int)issue.userid)</td> 

which populated following:

public static string getusernamebyid(int userid) {     return getuserbyid(userid).name; }  internal static userprofile getuserbyid(int userid) {     var db = new userscontext();     return db.userprofiles.where(c => c.userid == userid).single(); } 

when stepping through code userid correct, errors stating c.userid not exist in current context

however in accountmodels.cs shows

public class userscontext : dbcontext {     public userscontext()         : base("authcontext")     {     }      public dbset<userprofile> userprofiles { get; set; }     public dbset<usersinroles> usersinroles { get; set; }     public dbset<roles> roles { get; set; } }  [table("userprofile", schema = "dbo")] public class userprofile  {     [key]     [databasegeneratedattribute(databasegeneratedoption.identity)]     public int userid { get; set; }     public string username { get; set; }     public string name { get; set; }     public string email { get; set; }     public bool islockedout { get; set; } } 

what missing?

try update c.userid == userid condition you'll avoid such error:

c => c.userid != null && c.userid == userid