Pass IQueryable data by reference to event handler

Author: VladimirDimov

src/Examples/Examples.Mvc/Controllers/CustomersController.cs

@@ -46,11 +46,11 @@ public ActionResult GetCustomersData()
 
     public class CustomJQDataTableAttribute : JQDataTableAttribute
     {
-        public override void OnDataProcessed(object data, RequestInfoModel requestInfoModel)
+        public override void OnDataProcessed(ref object data, RequestInfoModel requestInfoModel)
         {
-            var processedData = ((IQueryable<CustomerViewModel>)data).Where(x => x.CustomerID > 10 && x.CustomerID < 20);
-            var list = processedData.ToList();
-            data = list;
+            var list = ((IQueryable<CustomerViewModel>)data).ToList();
+            list.ForEach(x => x.Person.FirstName = $"FN {x.Person.FirstName}");
+            data = list.AsQueryable();
         }
     }
 }

src/JQDT.MVC/JQDataTableAttribute.cs

@@ -40,7 +40,7 @@ public override void OnActionExecuted(ActionExecutedContext filterContext)
         /// </summary>
         /// <param name="data">The data.</param>
         /// <param name="requestInfoModel">The request information model.</param>
-        public virtual void OnDataProcessed(object data, RequestInfoModel requestInfoModel)
+        public virtual void OnDataProcessed(ref object data, RequestInfoModel requestInfoModel)
         {
         }
 

src/JQDT/Application/ApplicationBase.cs

@@ -52,7 +52,8 @@ public ResultModel Execute()
                 var dataProcessChain = this.GetDataProcessChain(requestModel.Helpers.DataCollectionType);
                 var processedData = dataProcessChain.ProcessData(data, requestModel);
 
-                this.OnDataProcessed(processedData, requestModel);
+                // Call on data processed event
+                this.PerformDataProcessorEventHandler(ref processedData, requestModel);
 
                 result.Data = processedData.ToList().Select(x => (object)x).ToList();
                 result.Draw = requestModel.TableParameters.Draw;
@@ -79,6 +80,18 @@ public ResultModel Execute()
         /// <returns>Data collection as <see cref="IQueryable{T}"/></returns>
         protected abstract IQueryable<T> GetData();
 
+        /// <summary>
+        /// Performs the data processor event handler. Boxes the data collection, pass it by reference and then unbox it.
+        /// </summary>
+        /// <param name="data">The data.</param>
+        /// <param name="requestInfoModel">The request information model.</param>
+        private void PerformDataProcessorEventHandler(ref IQueryable<T> data, RequestInfoModel requestInfoModel)
+        {
+            var dataAsObj = (object)data;
+            this.OnDataProcessed(ref dataAsObj, requestInfoModel);
+            data = (IQueryable<T>)dataAsObj;
+        }
+
         private string FormatException(Exception ex)
         {
             var builder = new StringBuilder();

src/JQDT/Delegates/DataProcessorEventHandler.cs

@@ -7,5 +7,5 @@
     /// </summary>
     /// <param name="data">The data.</param>
     /// <param name="requestInfoModel">The request information model.</param>
-    public delegate void DataProcessorEventHandler(object data, RequestInfoModel requestInfoModel);
+    public delegate void DataProcessorEventHandler(ref object data, RequestInfoModel requestInfoModel);
 }