Update dbbulkoperationconcurrency-exception.md

Author: JonathanMagnan

docs/pages/troubleshooting/dbbulkoperationconcurrency-exception.md

@@ -5,3 +5,86 @@ permalink: dbbulkoperationconcurrency-exception
 ---
 
 {% include template-h1.html %}
+
+## Problem
+
+You execute a method from the Entity Framework Extensions library, and the following error is thrown:
+
+- Type: DbBulkOperationConcurrencyException
+
+{% include template-exception.html message='A concurrency exception has occured. Entities may have been modified or deleted since entities were loaded.' %}
+
+## Solution
+
+### Cause
+
+Another thread have already performed the operation.
+
+### Fix
+
+There is three possible resolution:
+
+- Database Win
+- Client Win
+- Custom Resolution
+
+#### Database Win
+{% highlight csharp %}
+public void BulkUpdate_DatabaseWins<T>(CurrentContext ctx, List<T> list) where T : class
+{
+    try
+    {
+        ctx.BulkUpdate(list);
+    }
+    catch (DbBulkOperationConcurrencyException ex)
+    {
+        // DO nothing (or log), keep database values!
+    }
+}
+{% endhighlight %}
+
+#### Client Win
+{% highlight csharp %}
+public void BulkUpdate_StoreWins<T>(CurrentContext ctx, List<T> list) where T : class
+{
+    try
+    {
+        ctx.BulkUpdate(list);
+    }
+    catch (DbBulkOperationConcurrencyException ex)
+    {
+        // FORCE update store entities
+        ctx.BulkUpdate(list, operation => operation.AllowConcurrency = false);
+    }
+}
+{% endhighlight %}
+
+#### Custom Resolution
+{% highlight csharp %}
+public void BulkUpdate_CustomResolution<T>(CurrentContext ctx, List<T> list) where T : class
+{
+    try
+    {
+        ctx.BulkUpdate(list);
+    }
+    catch (DbBulkOperationConcurrencyException ex)
+    {
+        foreach (var entry in ex.Entries)
+        {
+            ObjectStateEntry objectEntry;
+
+            if (entry is EntitySimple_Concurrency)
+            {
+                var clientEntry = (EntitySimple_Concurrency) entry;
+                var databaseEntry = ctx.EntitySimple_Concurrencys.Single(x => x.ID == clientEntry.ID);
+
+                // merge properties like you want
+                clientEntry.IntColumn = databaseEntry.IntColumn + 303;
+            }
+        }
+
+        // FORCE update store entities
+        ctx.BulkUpdate(list, operation => operation.AllowConcurrency = false);
+    }
+}
+{% endhighlight %}