Perf: Save only when user updated

Disco.Models/Repository/User/User.cs

@@ -71,21 +71,40 @@ namespace Disco.Models.Repository
             return string.Format("{0} ({1})", this.DisplayName, this.UserId);
         }
 
-        public void UpdateSelf(User u)
+        public bool UpdateSelf(User u)
         {
+            var changed = false;
+
             if (!this.UserId.Equals(u.UserId, StringComparison.OrdinalIgnoreCase))
                 throw new ArgumentException("User Id's do not match", "u");
 
             if (this.Surname != u.Surname)
+            {
                 this.Surname = u.Surname;
+                changed = true;
+            }
             if (this.GivenName != u.GivenName)
+            {
                 this.GivenName = u.GivenName;
+                changed = true;
+            }
             if (this.DisplayName != u.DisplayName)
+            {
                 this.DisplayName = u.DisplayName;
+                changed = true;
+            }
             if (this.EmailAddress != u.EmailAddress)
+            {
                 this.EmailAddress = u.EmailAddress;
+                changed = true;
+            }
             if (this.PhoneNumber != u.PhoneNumber)
+            {
                 this.PhoneNumber = u.PhoneNumber;
+                changed = true;
+            }
+
+            return changed;
         }
     }
 }

Disco.Services/Devices/Exporting/DeviceExport.cs

@@ -33,14 +33,14 @@ namespace Disco.Services.Devices.Exporting
                 Options.AssignedUserEmailAddress)
             {
                 TaskStatus.UpdateStatus(20, "Updating Assigned User details");
-                var users = Devices.Where(d => d.AssignedUserId != null).Select(d => d.AssignedUserId).Distinct().ToList();
+                var users = Devices.Where(d => d.AssignedUserId != null).Select(d => d.AssignedUser).Distinct().ToList();
 
-                users.Select((userId, index) =>
+                users.Select((user, index) =>
                 {
-                    TaskStatus.UpdateStatus(20 + (((double)20 / users.Count) * index), string.Format("Updating Assigned User details: {0}", userId));
+                    TaskStatus.UpdateStatus(20 + (((double)20 / users.Count) * index), string.Format("Updating Assigned User details: {0}", user.UserId));
                     try
                     {
-                        return UserService.GetUser(userId, Database);
+                        return UserService.GetUser(user.UserId, Database);
                     }
                     catch (Exception) { return null; } // Ignore Errors
                 }).ToList();

Disco.Services/Users/UserService.cs

@@ -273,13 +273,18 @@ namespace Disco.Services.Users
                 // Update Repository
                 User existingUser = Database.Users.Find(user.UserId);
                 if (existingUser == null)
+                {
                     Database.Users.Add(user);
+                    Database.SaveChanges();
+                }
                 else
                 {
-                    existingUser.UpdateSelf(user);
+                    if (existingUser.UpdateSelf(user))
+                    {
+                        Database.SaveChanges();
+                    }
                     user = existingUser;
                 }
-                Database.SaveChanges();
 
                 var token = AuthorizationToken.BuildToken(user, adAccount.Groups.Select(g => g.Id));