(feature) Parser.AddCustomFilter added to perform extra filters on IQueryable maintaining total count

Author: oscarlocatelli

src/DatatablesParser/DatatablesParser.cs

@@ -10,6 +10,7 @@ namespace DataTablesParser
 {
     public class Parser<T> where T : class
     {
+        private IQueryable<T> _originalQuery;
         private IQueryable<T> _query;
         private readonly Dictionary<string,string> _config;
         private readonly Type _type;
@@ -42,6 +43,7 @@ public class Parser<T> where T : class
 
         public Parser(IEnumerable<KeyValuePair<string, StringValues>> configParams, IQueryable<T> query)
         {
+            _originalQuery = query;
             _query = query;
             _config = configParams.ToDictionary(k => k.Key,v=> v.Value.First().Trim());
             _type = typeof(T);
@@ -104,7 +106,7 @@ public Results<T> Parse()
             list.draw = int.Parse(_config[Constants.DRAW]);
 
             // count the record BEFORE filtering
-            list.recordsTotal =  _query.Count();
+            list.recordsTotal = _originalQuery.Count();
 
             //sort results if sorting isn't disabled or skip needs to be called
             if(!_sortDisabled || _skip > 0)
@@ -124,16 +126,19 @@ public Results<T> Parse()
                 resultQuery = _query.Where(entityFilter)
                             .Skip(_skip)
                             .Take(_take);
-                            
-                list.recordsFiltered =  _query.Count(entityFilter);           
+
+                list.recordsFiltered = _query.Count(entityFilter);
             }
             else
             {
                 resultQuery = _query
                             .Skip(_skip)
                             .Take(_take);
-                            
-                list.recordsFiltered =  list.recordsTotal;
+
+                if(_query == _originalQuery)
+                    list.recordsFiltered = list.recordsTotal;
+                else
+                    list.recordsFiltered = _query.Count();
 
             }
 
@@ -191,6 +196,17 @@ public Parser<T> SetEndsWithToken(string token)
             return this;
         }
 
+        /// <summary>
+        /// AddCustomFilter add external custom filter to handle complex filtering logic
+        /// For example date range filtering
+        /// </summary>
+        /// <param name="predicate">Filter logic</param>
+        /// <returns></returns>
+        public Parser<T> AddCustomFilter(Expression<Func<T, bool>> predicate)
+        {
+            _query = _query.Where(predicate);
+            return this;
+        }
 
         private void ApplySort()
         {
@@ -359,7 +375,7 @@ private Expression<Func<T, bool>> GenerateEntityFilter()
 
                     if(globalFilterConst!=null)
                     {
-                        var globalTest = Expression.Call(toLower, typeof(string).GetMethod(globalFilterFn, new[] { typeof(string) }), globalFilterConst);
+                        Expression globalTest = Expression.Call(toLower, typeof(string).GetMethod(globalFilterFn, new[] { typeof(string) }), globalFilterConst);
 
                         if(filterExpr == null)
                         {

test/DatatablesParser.Tests/MysqlEntityTests.cs

@@ -127,5 +127,28 @@ public void ResultsWhenSearchInNullColumnTest()
 
         }
 
+        [Fact]
+        public void AddCustomFilterTest()
+        {
+            var context = TestHelper.GetMysqlContext();
+            var p = TestHelper.CreateParams();
+            var displayLength = 2; // James and Tony
+
+
+            var parser = new Parser<Person>(p, context.People); // p is empty, all rows
+
+            var minDate = DateTime.Parse("1960-01-01");
+            var maxDate = DateTime.Parse("1970-01-01");
+            parser.AddCustomFilter(x => x.BirthDate >= minDate);
+            parser.AddCustomFilter(x => x.BirthDate < maxDate);
+
+            var result = parser.Parse().recordsFiltered;
+
+            Console.WriteLine("MySql - Search only born between 1960 and 1970: {0}", result);
+
+            Assert.Equal(displayLength, result);
+
+        }
+
     }
 }