should fix #2

PizzaBot/Services/PizzaDBService.cs

@@ -55,11 +55,6 @@ namespace PizzaBot.Services
                 ErrorMessage = "Request was null. If you see this, contact the admin!";
                 return null;
             }
-            if (_context.Requests.AsEnumerable().Contains(request, _reqNameEqualityComparer))
-            {
-                ErrorMessage = $"Request with name {request.Name} already exists. Use a different name!";
-                return null;
-            }
             if (request.Name == null || request.Name == "")
             {
                 ErrorMessage = "Request needs a name!";
@@ -76,10 +71,19 @@ namespace PizzaBot.Services
                 return null;
             }
 
+            lock (_context)
+            {
+                if (_context.Requests.AsEnumerable().Contains(request, _reqNameEqualityComparer))
+                {
+                    ErrorMessage = $"Request with name {request.Name} already exists. Use a different name!";
+                    return null;
+                }
+
                 //insert valid request
                 request.Id = _rnd.Next(int.MaxValue);
                 _context.Requests.Add(request);
                 _context.SaveChanges();
+            }
 
             _globalStuffService.ShouldBalance = true;
 
@@ -93,8 +97,11 @@ namespace PizzaBot.Services
                 Balance();
             }
 
+            lock (_context)
+            {
                 return _context.Requests.OrderBy(r => r.Name);
             }
+        }
 
         public IEnumerable<PizzaResult> GetAllResults()
         {
@@ -103,8 +110,11 @@ namespace PizzaBot.Services
                 Balance();
             }
 
+            lock (_context)
+            {
                 return _context.Results.ToList();
             }
+        }
 
         public PizzaResult? GetResultById(int id)
         {
@@ -113,18 +123,24 @@ namespace PizzaBot.Services
                 Balance();
             }
 
+            lock (_context)
+            {
                 return _context.Results.Find(id);
             }
+        }
 
         public PizzaRequest? GetRequestById(int id)
         {
-            if(_context.Requests.Find(id) == null)
+            lock (_context)
+            {
+                if (_context.Requests.Find(id) == null)
                 {
                     return null;
                 }
 
                 return _context.Requests.Find(id).GetShallowCopy();
             }
+        }
 
         public void DeleteById(int id)
         {
@@ -133,6 +149,8 @@ namespace PizzaBot.Services
                 return;
             }
 
+            lock (_context)
+            {
                 var request = _context.Requests.Find(id);
                 var result = _context.Results.Find(id);
 
@@ -149,6 +167,7 @@ namespace PizzaBot.Services
 
                 _context.SaveChanges();
             }
+        }
 
         public bool UpdateRequest(PizzaRequest request, out string ErrorMessage)
         {
@@ -170,9 +189,13 @@ namespace PizzaBot.Services
                 ErrorMessage = "Request needs to have at least one piece!";
                 return false;
             }
+
+            lock (_context)
+            {
                 _context.Requests.Remove(_context.Requests.Find(request.Id));
                 _context.Requests.Add(request);
                 _context.SaveChanges();
+            }
 
             _globalStuffService.ShouldBalance = true;
 
@@ -183,22 +206,28 @@ namespace PizzaBot.Services
         {
             Dictionary<int, PizzaRequest> orders = new Dictionary<int, PizzaRequest>();
 
+            lock (_context)
+            {
                 foreach (var request in _context.Requests.ToList())
                 {
                     orders.Add(request.Id, request);
                 }
+            }
 
                 var balancingResult = _balancingService.Distribute(orders);
 
+            lock (_context) {
                 _context.Results.RemoveRange(_context.Results.ToList());
                 _context.Results.AddRange(balancingResult.results.Values);
 
+                _context.SaveChanges();
+            }
+
             _globalStuffService.MeatPizzas = balancingResult.requiredMeat;
             _globalStuffService.VeggiePizzas = balancingResult.requiredVeggie;
             _globalStuffService.VeganPizzas = balancingResult.requiredVegan;
 
             _globalStuffService.TotalCost = balancingResult.totalCost;
-            _context.SaveChanges();
 
             _globalStuffService.ShouldBalance = false;
         }
@@ -212,23 +241,32 @@ namespace PizzaBot.Services
                 _globalStuffService.VeganPizzas = 0;
                 _globalStuffService.TotalCost = 0;
 
+                lock (_context)
+                {
                     _context.Requests.RemoveRange(_context.Requests);
                     _context.Results.RemoveRange(_context.Results);
                     _context.SaveChanges();
+                }
                 return true;
             }
             return false;
         }
 
         public void MarkAsPaid(int id)
+        {
+            lock (_context)
             {
                 _context.Results.Find(id).hasPaid = true;
                 _context.SaveChanges();
             }
+        }
         public void MarkAsNotPaid(int id)
+        {
+            lock (_context)
             {
                 _context.Results.Find(id).hasPaid = false;
                 _context.SaveChanges();
             }
         }
+    }
 }