diff --git a/src/admin/Bootstrap.DataAccess.MongoDB/Group.cs b/src/admin/Bootstrap.DataAccess.MongoDB/Group.cs
index e6d98d11..f43c960b 100644
--- a/src/admin/Bootstrap.DataAccess.MongoDB/Group.cs
+++ b/src/admin/Bootstrap.DataAccess.MongoDB/Group.cs
@@ -75,7 +75,8 @@ namespace Bootstrap.DataAccess.MongoDB
         {
             var groups = GroupHelper.Retrieves();
             var user = UserHelper.Retrieves().Cast<User>().FirstOrDefault(u => u.Id == userId);
-            groups.ToList().ForEach(g => g.Checked = user.Groups.Any(id => id == g.Id) ? "checked" : "");
+            if (user != null)
+                groups.ToList().ForEach(g => g.Checked = user.Groups.Any(id => id == g.Id) ? "checked" : "");
             return groups;
         }
 
@@ -140,10 +141,10 @@ namespace Bootstrap.DataAccess.MongoDB
         public override IEnumerable<BootstrapGroup> RetrievesByUserName(string userName)
         {
             var groups = new List<BootstrapGroup>();
-            var user = UserHelper.Retrieves().Cast<User>().FirstOrDefault(u => u.UserName == userName);
             var group = GroupHelper.Retrieves();
-
-            groups.AddRange(group.Where(g => user.Groups.Any(ug => ug == g.Id)));
+            var user = UserHelper.Retrieves().Cast<User>().FirstOrDefault(u => u.UserName == userName);
+            if (user != null)
+                groups.AddRange(group.Where(g => user.Groups.Any(ug => ug == g.Id)));
             return groups;
         }
     }
diff --git a/src/admin/Bootstrap.DataAccess.MongoDB/Role.cs b/src/admin/Bootstrap.DataAccess.MongoDB/Role.cs
index dd6b10dc..a1e0f49d 100644
--- a/src/admin/Bootstrap.DataAccess.MongoDB/Role.cs
+++ b/src/admin/Bootstrap.DataAccess.MongoDB/Role.cs
@@ -104,7 +104,8 @@ namespace Bootstrap.DataAccess.MongoDB
         {
             var roles = RoleHelper.Retrieves();
             var user = UserHelper.Retrieves().Cast<User>().FirstOrDefault(u => u.Id == userId);
-            roles.ToList().ForEach(r => r.Checked = user.Roles.Any(id => id == r.Id) ? "checked" : "");
+            if (user != null)
+                roles.ToList().ForEach(r => r.Checked = user.Roles.Any(id => id == r.Id) ? "checked" : "");
             return roles;
         }
 
@@ -188,7 +189,8 @@ namespace Bootstrap.DataAccess.MongoDB
         {
             var roles = RoleHelper.Retrieves();
             var group = GroupHelper.Retrieves().Cast<Group>().FirstOrDefault(u => u.Id == groupId);
-            roles.ToList().ForEach(r => r.Checked = group.Roles.Any(id => id == r.Id) ? "checked" : "");
+            if (group != null)
+                roles.ToList().ForEach(r => r.Checked = group.Roles.Any(id => id == r.Id) ? "checked" : "");
             return roles;
         }
 
diff --git a/src/admin/Bootstrap.DataAccess.MongoDB/User.cs b/src/admin/Bootstrap.DataAccess.MongoDB/User.cs
index 0d931cd7..b6d7e4f1 100644
--- a/src/admin/Bootstrap.DataAccess.MongoDB/User.cs
+++ b/src/admin/Bootstrap.DataAccess.MongoDB/User.cs
@@ -336,16 +336,19 @@ namespace Bootstrap.DataAccess.MongoDB
         public override bool Reject(string id, string rejectBy)
         {
             var user = UserHelper.RetrieveNewUsers().FirstOrDefault(u => u.Id == id);
-            DbManager.RejectUsers.InsertOne(new RejectUser()
+            if (user != null)
             {
-                DisplayName = user.DisplayName,
-                RegisterTime = user.RegisterTime,
-                RejectedBy = rejectBy,
-                RejectedReason = "",
-                RejectedTime = DateTime.Now,
-                UserName = user.UserName
-            });
-            DbManager.Users.DeleteOne(User => User.Id == id);
+                DbManager.RejectUsers.InsertOne(new RejectUser()
+                {
+                    DisplayName = user.DisplayName,
+                    RegisterTime = user.RegisterTime,
+                    RejectedBy = rejectBy,
+                    RejectedReason = "",
+                    RejectedTime = DateTime.Now,
+                    UserName = user.UserName
+                });
+                DbManager.Users.DeleteOne(User => User.Id == id);
+            }
             return true;
         }
     }