Fix: Duplicate Device Models

Stop future duplicate device models and repair any existing duplicates SEE: http://discoict.com.au/forum/support/2013/2/duplicate-device-models.aspx
2013-02-07 18:26:58 +11:00
parent d2805d8765
commit a9bbcabd87
3 changed files with 944 additions and 891 deletions
@@ -0,0 +1,61 @@
+using System;
+using System.Collections.Generic;
+using System.Data.Entity;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Disco.Data.Repository;
+using Disco.Models.Repository;
+
+namespace Disco.BI
+{
+    public static class DeviceModelBI
+    {
+
+        // Added: 2013-02-07 G#
+        // Ensure Duplicate Device Models are not created by creating only one Device Model at a time
+        // http://www.discoict.com.au/forum/support/2013/2/duplicate-device-models.aspx
+        // Thanks to Michael Vorster for reporting this problem.
+        private static object _CreateDeviceModelLock = new object();
+        public static Tuple<DeviceModel, bool> GetOrCreateDeviceModel(this DbSet<DeviceModel> DeviceModelsSet, string Manufacturer, string Model, string ModelType)
+        {
+            // Already Exists?
+            var deviceModel = DeviceModelsSet.FirstOrDefault(dm => dm.Manufacturer == Manufacturer && dm.Model == Model);
+            if (deviceModel == null)
+            {
+                // Ensure only one thread/request at a time
+                lock (_CreateDeviceModelLock)
+                {
+                    // Check again now that lock is enforced
+                    deviceModel = DeviceModelsSet.FirstOrDefault(dm => dm.Manufacturer == Manufacturer && dm.Model == Model);
+                    
+                    if (deviceModel == null)
+                    {
+                        // Create the Device Model in a different DataContext so we don't have to commit unrelated changes
+                        using (DiscoDataContext dbContext = new DiscoDataContext())
+                        {
+                            var addDeviceModel = new DeviceModel
+                            {
+                                Manufacturer = Manufacturer,
+                                Model = Model,
+                                ModelType = ModelType,
+                                Description = string.Format("{0} {1}", Manufacturer, Model)
+                            };
+                            dbContext.DeviceModels.Add(addDeviceModel);
+                            dbContext.SaveChanges();
+                        }
+
+                        // Obtain the Device Model with the in-scope DataContext
+                        // - Overhead acknowledged, but reasonable given the infrequency of occurrence
+                        deviceModel = DeviceModelsSet.FirstOrDefault(dm => dm.Manufacturer == Manufacturer && dm.Model == Model);
+                        return new Tuple<DeviceModel, bool>(deviceModel, true);
+                    }
+                }
+            }
+
+            return new Tuple<DeviceModel,bool>(deviceModel, false);
+        }
+        // Added: 2013-02-07 G#
+
+    }
+}