implement ability to filter int values using string operators

Sieve/Services/SieveProcessor.cs

@@ -202,13 +202,8 @@ namespace Sieve.Services
 
                             if (filterTerm.OperatorIsCaseInsensitive && !isFilterTermValueNull)
                             {
-                                propertyValue = Expression.Call(propertyValue,
+                                propertyValue = GetStringMethodExpression(propertyValue, "ToUpper");
-                                    typeof(string).GetMethods()
+                                filterValue = GetStringMethodExpression(filterValue, "ToUpper");
-                                        .First(m => m.Name == "ToUpper" && m.GetParameters().Length == 0));
-
-                                filterValue = Expression.Call(filterValue,
-                                    typeof(string).GetMethods()
-                                        .First(m => m.Name == "ToUpper" && m.GetParameters().Length == 0));
                             }
 
                             var expression = GetExpression(filterTerm, filterValue, propertyValue);
@@ -333,19 +328,30 @@ namespace Sieve.Services
                 FilterOperator.LessThan => Expression.LessThan(propertyValue, filterValue),
                 FilterOperator.GreaterThanOrEqualTo => Expression.GreaterThanOrEqual(propertyValue, filterValue),
                 FilterOperator.LessThanOrEqualTo => Expression.LessThanOrEqual(propertyValue, filterValue),
-                FilterOperator.Contains => Expression.Call(propertyValue,
+                FilterOperator.Contains => GetStringMethodExpression(filterValue, propertyValue, "Contains"),
-                    typeof(string).GetMethods().First(m => m.Name == "Contains" && m.GetParameters().Length == 1),
+                FilterOperator.StartsWith => GetStringMethodExpression(filterValue, propertyValue, "StartsWith"),
-                    filterValue),
+                FilterOperator.EndsWith => GetStringMethodExpression(filterValue, propertyValue, "EndsWith"),
-                FilterOperator.StartsWith => Expression.Call(propertyValue,
-                    typeof(string).GetMethods().First(m => m.Name == "StartsWith" && m.GetParameters().Length == 1),
-                    filterValue),
-                FilterOperator.EndsWith => Expression.Call(propertyValue,
-                typeof(string).GetMethods().First(m => m.Name == "EndsWith" && m.GetParameters().Length == 1),
-                filterValue),
                 _ => Expression.Equal(propertyValue, filterValue)
             };
         }
 
+        private static Expression GetStringMethodExpression(dynamic filterValue, dynamic propertyValue, string methodName) =>
+            propertyValue.Type == typeof(string) && filterValue.Type == typeof(string)
+                ? Expression.Call(propertyValue, GetStringMethod(methodName, 1), filterValue)
+                : Expression.Call(CallToString(propertyValue), GetStringMethod(methodName, 1), CallToString(filterValue));
+
+        private static Expression GetStringMethodExpression(dynamic propertyValue, string methodName) =>
+            propertyValue.Type == typeof(string)
+                ? Expression.Call(propertyValue, GetStringMethod(methodName, 0))
+                : Expression.Call(CallToString(propertyValue), GetStringMethod(methodName, 0));
+
+        private static Expression CallToString(dynamic value) =>
+            Expression.Call(value, typeof(object).GetMethod("ToString"));
+
+        private static MethodInfo GetStringMethod(string methodName, int paramCount) =>
+            typeof(string).GetMethods()
+                .First(m => m.Name == methodName && m.GetParameters().Length == paramCount);
+
         // Workaround to ensure that the filter value gets passed as a parameter in generated SQL from EF Core
         private static Expression GetClosureOverConstant<T>(T constant, Type targetType)
         {

SieveUnitTests/General.cs

@@ -39,7 +39,7 @@ namespace SieveUnitTests
                 {
                     Id = 0,
                     Title = "A",
-                    LikeCount = 100,
+                    LikeCount = 500,
                     IsDraft = true,
                     CategoryId = null,
                     TopComment = new Comment { Id = 0, Text = "A1" },
@@ -255,6 +255,108 @@ namespace SieveUnitTests
             Assert.True(nullableResult.Count() == 3);
         }
         
+        [Theory]
+        [InlineData(5)]
+        [InlineData(0)]
+        public void CanFilterIntsUsingContainsOperator(int likeCount)
+        {
+            var model = new SieveModel
+            {
+                Filters = $"LikeCount@={likeCount}"
+            };
+        
+            var result = _processor.Apply(model, _posts);
+        
+            Assert.True(result.Count() == 3);
+        }
+        
+        [Theory]
+        [InlineData(5)]
+        [InlineData(0)]
+        public void CanFilterIntsUsingCaseInsensitiveContainsOperator(int likeCount)
+        {
+            var model = new SieveModel
+            {
+                Filters = $"LikeCount@=*{likeCount}"
+            };
+        
+            var result = _processor.Apply(model, _posts);
+        
+            Assert.True(result.Count() == 3);
+        }
+        
+        [Theory]
+        [InlineData(5)]
+        [InlineData(0)]
+        public void CanFilterIntsUsingDoesNotContainsOperator(int likeCount)
+        {
+            var model = new SieveModel
+            {
+                Filters = $"LikeCount!@={likeCount}"
+            };
+        
+            var result = _processor.Apply(model, _posts);
+        
+            Assert.True(result.Count() == 2);
+        }
+        
+        [Theory]
+        [InlineData(5)]
+        [InlineData(0)]
+        public void CanFilterIntsUsingCaseInsensitiveDoesNotContainsOperator(int likeCount)
+        {
+            var model = new SieveModel
+            {
+                Filters = $"LikeCount!@=*{likeCount}"
+            };
+        
+            var result = _processor.Apply(model, _posts);
+        
+            Assert.True(result.Count() == 2);
+        }
+        
+        [Theory]
+        [InlineData(5)]
+        public void CanFilterIntsUsingCaseInsensitiveDoesNotStartsWithOperator(int likeCount)
+        {
+            var model = new SieveModel
+            {
+                Filters = $"LikeCount!_=*{likeCount}"
+            };
+        
+            var result = _processor.Apply(model, _posts);
+        
+            Assert.True(result.Count() == 2);
+        }
+        
+        [Theory]
+        [InlineData(5)]
+        public void CanFilterIntsUsingStartsWithOperator(int likeCount)
+        {
+            var model = new SieveModel
+            {
+                Filters = $"LikeCount_={likeCount}"
+            };
+        
+            var result = _processor.Apply(model, _posts);
+        
+            Assert.True(result.Count() == 3);
+        }
+        
+        [Theory]
+        [InlineData(0)]
+        public void CanFilterIntsUsingEndsWithOperator(int likeCount)
+        {
+            var model = new SieveModel
+            {
+                Filters = $"LikeCount_-={likeCount}"
+            };
+        
+            var result = _processor.Apply(model, _posts);
+        
+            Assert.True(result.Count() == 3);
+        }
+
         [Theory]
         [InlineData(@"Text@=*\,")]
         [InlineData(@"Text@=*\, ")]