в догонку

DepartmentPortal/Common/DatabaseCore/DatabaseContext.cs

@@ -30,6 +30,8 @@ namespace DatabaseCore
 
 			modelBuilder.Entity<Role>().HasIndex(s => s.RoleName).IsUnique();
 
+			modelBuilder.Entity<User>().HasIndex(s => s.UserName;
+
 			modelBuilder.Entity<EmployeePost>().HasIndex(s => s.EmployeePostName).IsUnique();
 
 			modelBuilder.Entity<Employee>().HasIndex(p => new { p.FirstName, p.LastName, p.Patronymic }).IsUnique();