feat(operator): implement EndsWith #85 (#173)

add a new operator
adapt sieve processor
update regex operator to split received filter value
add unit tests & adjust existing ones

Co-authored-by: Erwan RAULO <Erwan.RAULO@vinci-energies.net>

README.md

@@ -129,7 +129,8 @@ Then you can add the configuration:
         "DefaultPageSize": "int number: optional number to fallback to when no page argument is given. Set <=0 to disable paging if no pageSize is specified (default).",
         "MaxPageSize": "int number: maximum allowed page size. Set <=0 to make infinite (default)",
         "ThrowExceptions": "boolean: should Sieve throw exceptions instead of silently failing? Defaults to false",
-        "IgnoreNullsOnNotEqual": "boolean: ignore null values when filtering using is not equal operator? Default to true"
+        "IgnoreNullsOnNotEqual": "boolean: ignore null values when filtering using is not equal operator? Defaults to true",
+        "DisableNullableTypeExpressionForSorting": "boolean: disable the creation of nullable type expression for sorting. Some databases do not handle it (yet). Defaults to false"
     }
 }
 ```
@@ -159,7 +160,10 @@ More formally:
 * `pageSize` is the number of items returned per page 
 
 Notes:
-* You can use backslashes to escape commas and pipes within value fields
+* You can use backslashes to escape special characters and sequences:
+    * commas: `Title@=some\,title` makes a match with "some,title"
+    * pipes: `Title@=some\|title` makes a match with "some|title"
+    * null values: `Title@=\null` will search for items with title equal to "null" (not a missing value, but "null"-string literally)
 * You can have spaces anywhere except *within* `{Name}` or `{Operator}` fields
 * If you need to look at the data before applying pagination (eg. get total count), use the optional paramters on `Apply` to defer pagination (an [example](https://github.com/Biarity/Sieve/issues/34))
 * Here's a [good example on how to work with enumerables](https://github.com/Biarity/Sieve/issues/2)
@@ -204,10 +208,13 @@ You can replace this DSL with your own (eg. use JSON instead) by implementing an
 | `<=`       | Less than or equal to    |
 | `@=`       | Contains                 |
 | `_=`       | Starts with              |
+| `_-=`      | Ends with                |
 | `!@=`      | Does not Contains        |
 | `!_=`      | Does not Starts with     |
+| `!_-=`     | Does not Ends with       |
 | `@=*`      | Case-insensitive string Contains |
 | `_=*`      | Case-insensitive string Starts with |
+| `_-=*`     | Case-insensitive string Ends with |
 | `==*`      | Case-insensitive string Equals |
 | `!=*`      | Case-insensitive string Not equals |
 | `!@=*`     | Case-insensitive string does not Contains |
@@ -228,7 +235,7 @@ It is recommended that you write exception-handling middleware to globally handl
 You can find an example project incorporating most Sieve concepts in [SieveTests](https://github.com/Biarity/Sieve/tree/master/SieveTests).
 
 ## Fluent API
-To use the Fluent API instead of attributes in marking properties, setup an alternative `SieveProcessor` that overrides `MapProperties`. For example:
+To use the Fluent API instead of attributes in marking properties, setup an alternative `SieveProcessor` that overrides `MapProperties`. For [example](https://github.com/Biarity/Sieve/blob/master/Sieve.Sample/Services/ApplicationSieveProcessor.cs):
 
 ```C#
 public class ApplicationSieveProcessor : SieveProcessor
@@ -260,13 +267,78 @@ public class ApplicationSieveProcessor : SieveProcessor
 }
 ```
 
+
+
 Now you should inject the new class instead:
 ```C#
 services.AddScoped<ISieveProcessor, ApplicationSieveProcessor>();
 ```
-
 Find More on Sieve's Fluent API [here](https://github.com/Biarity/Sieve/issues/4#issuecomment-364629048).
 
+### Modular Fluent API configuration
+Adding all fluent mappings directly in the processor can become unwieldy on larger projects.
+It can also clash with vertical architectures.
+To enable functional grouping of mappings the `ISieveConfiguration` interface was created together with extensions to the default mapper.
+```C#
+public class SieveConfigurationForPost : ISieveConfiguration
+{
+    public void Configure(SievePropertyMapper mapper)
+    {
+        mapper.Property<Post>(p => p.Title)
+            .CanFilter()
+            .HasName("a_different_query_name_here");
+
+        mapper.Property<Post>(p => p.CommentCount)
+            .CanSort();
+
+        mapper.Property<Post>(p => p.DateCreated)
+            .CanSort()
+            .CanFilter()
+            .HasName("created_on");
+
+        return mapper;
+    }
+}
+```
+With the processor simplified to:
+```C#
+public class ApplicationSieveProcessor : SieveProcessor
+{
+    public ApplicationSieveProcessor(
+        IOptions<SieveOptions> options, 
+        ISieveCustomSortMethods customSortMethods, 
+        ISieveCustomFilterMethods customFilterMethods) 
+        : base(options, customSortMethods, customFilterMethods)
+    {
+    }
+
+    protected override SievePropertyMapper MapProperties(SievePropertyMapper mapper)
+    {
+        return mapper
+            .ApplyConfiguration<SieveConfigurationForPost>()
+            .ApplyConfiguration<SieveConfigurationForComment>();       
+    }
+}
+```
+There is also the option to scan and add all configurations for a given assembly
+```C#
+public class ApplicationSieveProcessor : SieveProcessor
+{
+    public ApplicationSieveProcessor(
+        IOptions<SieveOptions> options, 
+        ISieveCustomSortMethods customSortMethods, 
+        ISieveCustomFilterMethods customFilterMethods) 
+        : base(options, customSortMethods, customFilterMethods)
+    {
+    }
+
+    protected override SievePropertyMapper MapProperties(SievePropertyMapper mapper)
+    {
+        return mapper.ApplyConfigurationsFromAssembly(typeof(ApplicationSieveProcessor).Assembly);            
+    }
+}
+```
+
 ## Upgrading to v2.2.0
 
 2.2.0 introduced OR logic for filter values. This means your custom filters will need to accept multiple values rather than just the one.

Sieve.Sample/Entities/SieveConfigurationForPost.cs

@@ -0,0 +1,15 @@
+using Sieve.Services;
+
+namespace Sieve.Sample.Entities
+{
+    public class SieveConfigurationForPost : ISieveConfiguration
+    {
+        public void Configure(SievePropertyMapper mapper)
+        {
+            mapper.Property<Post>(p => p.Title)
+                .CanSort()
+                .CanFilter()
+                .HasName("CustomTitleName");
+        }
+    }
+}

Sieve.Sample/Services/ApplicationSieveProcessor.cs

@@ -13,11 +13,18 @@ namespace Sieve.Sample.Services
 
         protected override SievePropertyMapper MapProperties(SievePropertyMapper mapper)
         {
+            // Option 1: Map all properties centrally
             mapper.Property<Post>(p => p.Title)
                 .CanSort()
                 .CanFilter()
                 .HasName("CustomTitleName");
 
+            // Option 2: Manually apply functionally grouped mapping configurations
+            //mapper.ApplyConfiguration<SieveConfigurationForPost>();
+            
+            // Option 3: Scan and apply all configurations
+            //mapper.ApplyConfigurationsFromAssembly(typeof(ApplicationSieveProcessor).Assembly);
+
             return mapper;
         }
     }

Sieve/Extensions/OrderByDynamic.cs

@@ -12,9 +12,10 @@ namespace Sieve.Extensions
             string fullPropertyName,
             PropertyInfo propertyInfo,
             bool desc,
-            bool useThenBy)
+            bool useThenBy, 
+            bool disableNullableTypeExpression = false)
         {
-            var lambda = GenerateLambdaWithSafeMemberAccess<TEntity>(fullPropertyName, propertyInfo);
+            var lambda = GenerateLambdaWithSafeMemberAccess<TEntity>(fullPropertyName, propertyInfo, disableNullableTypeExpression);
 
             var command = desc
                 ? (useThenBy ? "ThenByDescending" : "OrderByDescending")
@@ -33,7 +34,8 @@ namespace Sieve.Extensions
         private static Expression<Func<TEntity, object>> GenerateLambdaWithSafeMemberAccess<TEntity>
         (
             string fullPropertyName,
-            PropertyInfo propertyInfo
+            PropertyInfo propertyInfo,
+            bool disableNullableTypeExpression
         )
         {
             var parameter = Expression.Parameter(typeof(TEntity), "e");
@@ -52,7 +54,7 @@ namespace Sieve.Extensions
                     propertyValue = Expression.MakeMemberAccess(propertyValue, propertyInfo);
                 }
 
-                if (propertyValue.Type.IsNullable())
+                if (propertyValue.Type.IsNullable() && !disableNullableTypeExpression)
                 {
                     nullCheck = GenerateOrderNullCheckExpression(propertyValue, nullCheck);
                 }

Sieve/Models/FilterOperator.cs

@@ -10,5 +10,6 @@
         LessThanOrEqualTo,
         Contains,
         StartsWith,
+        EndsWith,
     }
 }

Sieve/Models/FilterTerm.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Text.RegularExpressions;
 
@@ -6,50 +7,49 @@ namespace Sieve.Models
 {
     public class FilterTerm : IFilterTerm, IEquatable<FilterTerm>
     {
-        public FilterTerm() { }
+        private const string EscapedPipePattern = @"(?<!($|[^\\]|^)(\\\\)*?\\)\|";
+        private const string OperatorsRegEx = @"(!@=\*|!_=\*|!_-=\*|!=\*|!@=|!_=|!_-=|==\*|@=\*|_=\*|_-=\*|==|!=|>=|<=|>|<|@=|_=|_-=)";
+        private const string EscapeNegPatternForOper = @"(?<!\\)" + OperatorsRegEx;
+        private const string EscapePosPatternForOper = @"(?<=\\)" + OperatorsRegEx;
 
-        private const string EscapedPipePattern = @"(?<!($|[^\\])(\\\\)*?\\)\|";
-        private const string PipeToEscape = @"\|";
-
-        private static readonly string[] Operators = new string[] {
-                    "!@=*",
-                    "!_=*",
-                    "!=*",
-                    "!@=",
-                    "!_=",
-                    "==*",
-                    "@=*",
-                    "_=*",
-                    "==",
-                    "!=",
-                    ">=",
-                    "<=",
-                    ">",
-                    "<",
-                    "@=",
-                    "_="
+        private static readonly HashSet<string> _escapedSequences = new HashSet<string>
+        {
+            @"\|",
+            @"\\"
         };
 
         public string Filter
         {
             set
             {
-                var filterSplits = value.Split(Operators, StringSplitOptions.RemoveEmptyEntries)
-                    .Select(t => t.Trim()).ToArray();
+                var filterSplits = Regex.Split(value, EscapeNegPatternForOper).Select(t => t.Trim()).ToArray();
+
                 Names = Regex.Split(filterSplits[0], EscapedPipePattern).Select(t => t.Trim()).ToArray();
-                Values = filterSplits.Length > 1
-                    ? Regex.Split(filterSplits[1], EscapedPipePattern)
-                        .Select(t => t.Replace(PipeToEscape, "|").Trim())
-                        .ToArray()
-                    : null;
-                Operator = Array.Find(Operators, o => value.Contains(o)) ?? "==";
+
+                if (filterSplits.Length > 2)
+                {
+                    foreach (var match in Regex.Matches(filterSplits[2], EscapePosPatternForOper))
+                    {
+                        var matchStr = match.ToString();
+                        filterSplits[2] = filterSplits[2].Replace('\\' + matchStr, matchStr);
+                    }
+
+                    Values = Regex.Split(filterSplits[2], EscapedPipePattern)
+                        .Select(UnEscape)
+                        .ToArray();
+                }
+
+                Operator = Regex.Match(value, EscapeNegPatternForOper).Value;
                 OperatorParsed = GetOperatorParsed(Operator);
                 OperatorIsCaseInsensitive = Operator.EndsWith("*");
                 OperatorIsNegated = OperatorParsed != FilterOperator.NotEquals && Operator.StartsWith("!");
             }
-
         }
 
+        private string UnEscape(string escapedTerm)
+            => _escapedSequences.Aggregate(escapedTerm,
+                (current, sequence) => Regex.Replace(current, $@"(\\)({sequence})", "$2"));
+
         public string[] Names { get; private set; }
 
         public FilterOperator OperatorParsed { get; private set; }
@@ -80,6 +80,9 @@ namespace Sieve.Models
                 case "_=":
                 case "!_=":
                     return FilterOperator.StartsWith;
+                case "_-=":
+                case "!_-=":
+                    return FilterOperator.EndsWith;
                 default:
                     return FilterOperator.Equals;
             }

Sieve/Models/SieveOptions.cs

@@ -11,5 +11,7 @@
         public bool ThrowExceptions { get; set; } = false;
 
         public bool IgnoreNullsOnNotEqual { get; set; } = true;
+
+        public bool DisableNullableTypeExpressionForSorting { get; set; } = false;
     }
 }

Sieve/Services/ISieveConfiguration.cs

@@ -0,0 +1,70 @@
+#nullable enable
+using System;
+using System.Linq;
+using System.Reflection;
+
+namespace Sieve.Services
+{
+    /// <summary>
+    /// Use this interface to create SieveConfiguration (just like EntityTypeConfigurations are defined for EF)
+    /// </summary>
+    public interface ISieveConfiguration
+    {
+        /// <summary>
+        ///  Configures sieve property mappings.
+        /// </summary>
+        /// <param name="mapper"> The mapper used to configure the sieve properties on. </param>
+        void Configure(SievePropertyMapper mapper);
+    }
+
+    /// <summary>
+    /// Configuration extensions to the <see cref="SievePropertyMapper" />
+    /// </summary>
+    public static class SieveConfigurationExtensions
+    {
+        /// <summary>
+        ///     Applies configuration that is defined in an <see cref="ISieveConfiguration" /> instance.
+        /// </summary>
+        /// <param name="mapper"> The mapper to apply the configuration on. </param>
+        /// <typeparam name="T">The configuration to be applied. </typeparam>
+        /// <returns>
+        ///     The same <see cref="SievePropertyMapper" /> instance so that additional configuration calls can be chained.
+        /// </returns>
+        public static SievePropertyMapper ApplyConfiguration<T>(this SievePropertyMapper mapper) where T : ISieveConfiguration, new()
+        {
+            var configuration = new T();
+            configuration.Configure(mapper);
+            return mapper;
+        }
+
+        /// <summary>
+        ///     Applies configuration from all <see cref="ISieveConfiguration" />
+        ///     instances that are defined in provided assembly.
+        /// </summary>
+        /// <param name="mapper"> The mapper to apply the configuration on. </param>
+        /// <param name="assembly"> The assembly to scan. </param>
+        /// <returns>
+        ///     The same <see cref="SievePropertyMapper" /> instance so that additional configuration calls can be chained.
+        /// </returns>
+        public static SievePropertyMapper ApplyConfigurationsFromAssembly(this SievePropertyMapper mapper, Assembly assembly)
+        {
+            foreach (var type in assembly.GetTypes().Where(t => !t.IsAbstract && !t.IsGenericTypeDefinition))
+            {
+                // Only accept types that contain a parameterless constructor, are not abstract.
+                var noArgConstructor = type.GetConstructor(Type.EmptyTypes);
+                if (noArgConstructor is null)
+                {
+                    continue;
+                }
+
+                if (type.GetInterfaces().Any(t => t == typeof(ISieveConfiguration)))
+                {
+                    var configuration = (ISieveConfiguration)noArgConstructor.Invoke(new object?[] { });
+                    configuration.Configure(mapper);
+                }
+            }
+
+            return mapper;
+        }
+    }
+}

Sieve/Services/SieveProcessor.cs

@@ -68,6 +68,7 @@ namespace Sieve.Services
         where TSortTerm : ISortTerm, new()
     {
         private const string NullFilterValue = "null";
+        private const char EscapeChar = '\\';
         private readonly ISieveCustomSortMethods _customSortMethods;
         private readonly ISieveCustomFilterMethods _customFilterMethods;
         private readonly SievePropertyMapper _mapper = new SievePropertyMapper();
@@ -199,7 +200,7 @@ namespace Sieve.Services
                                 ? Expression.Constant(null, property.PropertyType)
                                 : ConvertStringValueToConstantExpression(filterTermValue, property, converter);
 
-                            if (filterTerm.OperatorIsCaseInsensitive)
+                            if (filterTerm.OperatorIsCaseInsensitive && !isFilterTermValueNull)
                             {
                                 propertyValue = Expression.Call(propertyValue,
                                     typeof(string).GetMethods()
@@ -311,6 +312,10 @@ namespace Sieve.Services
         private static Expression ConvertStringValueToConstantExpression(string value, PropertyInfo property,
             TypeConverter converter)
         {
+            // to allow user to distinguish between prop==null (as null) and prop==\null (as "null"-string)
+            value = value.Equals(EscapeChar + NullFilterValue, StringComparison.InvariantCultureIgnoreCase) 
+                ? value.TrimStart(EscapeChar) 
+                : value;
             dynamic constantVal = converter.CanConvertFrom(typeof(string))
                 ? converter.ConvertFrom(value)
                 : Convert.ChangeType(value, property.PropertyType);
@@ -334,6 +339,9 @@ namespace Sieve.Services
                 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)
             };
         }
@@ -360,7 +368,7 @@ namespace Sieve.Services
 
                 if (property != null)
                 {
-                    result = result.OrderByDynamic(fullName, property, sortTerm.Descending, useThenBy);
+                    result = result.OrderByDynamic(fullName, property, sortTerm.Descending, useThenBy, Options.Value.DisableNullableTypeExpressionForSorting);
                 }
                 else
                 {

SieveUnitTests/Abstractions/Entity/SieveConfigurationForIPost.cs

@@ -0,0 +1,37 @@
+using Sieve.Services;
+
+namespace SieveUnitTests.Abstractions.Entity
+{
+    public class SieveConfigurationForIPost : ISieveConfiguration
+    {
+        public void Configure(SievePropertyMapper mapper)
+        {
+            mapper.Property<IPost>(p => p.ThisHasNoAttributeButIsAccessible)
+                .CanSort()
+                .CanFilter()
+                .HasName("shortname");
+            
+            mapper.Property<IPost>(p => p.TopComment.Text)
+                .CanFilter();
+
+            mapper.Property<IPost>(p => p.TopComment.Id)
+                .CanSort();
+
+            mapper.Property<IPost>(p => p.OnlySortableViaFluentApi)
+                .CanSort();
+
+            mapper.Property<IPost>(p => p.TopComment.Text)
+                .CanFilter()
+                .HasName("topc");
+
+            mapper.Property<IPost>(p => p.FeaturedComment.Text)
+                .CanFilter()
+                .HasName("featc");
+
+            mapper
+                .Property<IPost>(p => p.DateCreated)
+                .CanSort()
+                .HasName("CreateDate");
+        }
+    }
+}

SieveUnitTests/Entities/SieveConfigurationForPost.cs

@@ -0,0 +1,37 @@
+using Sieve.Services;
+
+namespace SieveUnitTests.Entities
+{
+    public class SieveConfigurationForPost : ISieveConfiguration
+    {
+        public void Configure(SievePropertyMapper mapper)
+        {
+            mapper.Property<Post>(p => p.ThisHasNoAttributeButIsAccessible)
+                .CanSort()
+                .CanFilter()
+                .HasName("shortname");
+
+            mapper.Property<Post>(p => p.TopComment.Text)
+                .CanFilter();
+
+            mapper.Property<Post>(p => p.TopComment.Id)
+                .CanSort();
+
+            mapper.Property<Post>(p => p.OnlySortableViaFluentApi)
+                .CanSort();
+
+            mapper.Property<Post>(p => p.TopComment.Text)
+                .CanFilter()
+                .HasName("topc");
+
+            mapper.Property<Post>(p => p.FeaturedComment.Text)
+                .CanFilter()
+                .HasName("featc");
+
+            mapper
+                .Property<Post>(p => p.DateCreated)
+                .CanSort()
+                .HasName("CreateDate");
+        }
+    }
+}

SieveUnitTests/General.cs

@@ -74,6 +74,16 @@ namespace SieveUnitTests
                     TopComment = new Comment { Id = 1, Text = "D1" },
                     FeaturedComment = new Comment { Id = 7, Text = "D2" }
                 },
+                new Post
+                {
+                    Id = 4,
+                    Title = "Yen",
+                    LikeCount = 5,
+                    IsDraft = true,
+                    CategoryId = 5,
+                    TopComment = new Comment { Id = 4, Text = "Yen3" },
+                    FeaturedComment = new Comment { Id = 8, Text = "Yen4" }
+                }
             }.AsQueryable();
 
             _comments = new List<Comment>
@@ -124,7 +134,43 @@ namespace SieveUnitTests
             var result = _processor.Apply(model, _posts);
 
             Assert.Equal(1, result.First().Id);
-            Assert.True(result.Count() == 3);
+            Assert.True(result.Count() == 4);
+        }
+
+        [Fact]
+        public void EndsWithWorks()
+        {
+            var model = new SieveModel
+            {
+                Filters = "Title_-=n"
+            };
+
+            _testOutputHelper.WriteLine(model.GetFiltersParsed()[0].Values.ToString());
+            _testOutputHelper.WriteLine(model.GetFiltersParsed()[0].Operator);
+            _testOutputHelper.WriteLine(model.GetFiltersParsed()[0].OperatorParsed.ToString());
+
+            var result = _processor.Apply(model, _posts);
+
+            Assert.Equal(4, result.First().Id);
+            Assert.True(result.Count() == 1);
+        }
+
+        [Fact]
+        public void EndsWithCanBeCaseInsensitive()
+        {
+            var model = new SieveModel
+            {
+                Filters = "Title_-=*N"
+            };
+
+            _testOutputHelper.WriteLine(model.GetFiltersParsed()[0].Values.ToString());
+            _testOutputHelper.WriteLine(model.GetFiltersParsed()[0].Operator);
+            _testOutputHelper.WriteLine(model.GetFiltersParsed()[0].OperatorParsed.ToString());
+
+            var result = _processor.Apply(model, _posts);
+
+            Assert.Equal(4, result.First().Id);
+            Assert.True(result.Count() == 1);
         }
 
         [Fact]
@@ -150,7 +196,7 @@ namespace SieveUnitTests
 
             var result = _processor.Apply(model, _posts);
 
-            Assert.True(result.Count() == 3);
+            Assert.True(result.Count() == 4);
         }
 
         [Fact]
@@ -205,8 +251,8 @@ namespace SieveUnitTests
             var result = _processor.Apply(model, _posts);
             var nullableResult = _nullableProcessor.Apply(model, _posts);
 
-            Assert.True(result.Count() == 1);
-            Assert.True(nullableResult.Count() == 2);
+            Assert.True(result.Count() == 2);
+            Assert.True(nullableResult.Count() == 3);
         }
 
         [Theory]
@@ -255,7 +301,7 @@ namespace SieveUnitTests
             var result = _processor.Apply(model, _posts);
 
             Assert.False(result.Any(p => p.Id == 0));
-            Assert.True(result.Count() == 3);
+            Assert.True(result.Count() == 4);
         }
 
         [Fact]
@@ -474,11 +520,12 @@ namespace SieveUnitTests
             };
 
             var result = _processor.Apply(model, _posts);
-            Assert.Equal(3, result.Count());
+            Assert.Equal(4, result.Count());
             var posts = result.ToList();
             Assert.Contains("B", posts[0].TopComment.Text);
             Assert.Contains("C", posts[1].TopComment.Text);
             Assert.Contains("D", posts[2].TopComment.Text);
+            Assert.Contains("Yen", posts[3].TopComment.Text);
         }
 
         [Fact]
@@ -490,12 +537,13 @@ namespace SieveUnitTests
             };
 
             var result = _processor.Apply(model, _posts);
-            Assert.Equal(4, result.Count());
+            Assert.Equal(5, result.Count());
             var posts = result.ToList();
             Assert.Equal(0, posts[0].Id);
             Assert.Equal(3, posts[1].Id);
             Assert.Equal(2, posts[2].Id);
             Assert.Equal(1, posts[3].Id);
+            Assert.Equal(4, posts[4].Id);
         }
 
         [Fact]
@@ -630,13 +678,15 @@ namespace SieveUnitTests
             };
 
             var result = _processor.Apply(model, _posts);
-            Assert.Equal(4, result.Count());
+            Assert.Equal(5, result.Count());
 
             var posts = result.ToList();
-            Assert.Equal(3,posts[0].Id);
-            Assert.Equal(2,posts[1].Id);
-            Assert.Equal(1,posts[2].Id);
-            Assert.Equal(0,posts[3].Id);
+            Assert.Equal(4, posts[0].Id);
+            Assert.Equal(3,posts[1].Id);
+            Assert.Equal(2,posts[2].Id);
+            Assert.Equal(1,posts[3].Id);
+            Assert.Equal(0,posts[4].Id);
+
         }
 
         [Fact]
@@ -684,15 +734,119 @@ namespace SieveUnitTests
                     DateCreated = DateTimeOffset.UtcNow.AddDays(-1),
                     Text = "Here is | another comment"
                 },
+                new Comment
+                {
+                    Id = 2,
+                    DateCreated = DateTimeOffset.UtcNow.AddDays(-1),
+                    Text = @"Here is \| another comment(1)"
+                }
             }.AsQueryable();
 
-            var model = new SieveModel()
+            var model = new SieveModel
             {
-                Filters = "Text==Here is \\| a comment|Here is \\| another comment",
+                Filters = @"Text==Here is \| a comment|Here is \| another comment|Here is \\\| another comment(1)",
             };
 
             var result = _processor.Apply(model, comments);
-            Assert.Equal(2, result.Count());
+            Assert.Equal(3, result.Count());
         }
+        
+        [Theory]
+        [InlineData("CategoryId==1,(CategoryId|LikeCount)==50")]
+        [InlineData("(CategoryId|LikeCount)==50,CategoryId==1")]
+        public void CanFilterWithEscape(string filter)
+        {
+            var model = new SieveModel
+            {
+                Filters = filter
+            };
+
+            var result = _processor.Apply(model, _posts);
+            var entry = result.FirstOrDefault();
+            var resultCount = result.Count();
+
+            Assert.NotNull(entry);
+            Assert.Equal(1, resultCount);
+        }
+        
+        [Theory]
+        [InlineData(@"Title@=\\")]
+        public void CanFilterWithEscapedBackSlash(string filter)
+        {
+            var posts = new List<Post>
+            {
+                new Post
+                {
+                    Id = 1,
+                    Title = "E\\",
+                    LikeCount = 4,
+                    IsDraft = true,
+                    CategoryId = 1,
+                    TopComment = new Comment { Id = 1, Text = "E1" },
+                    FeaturedComment = new Comment { Id = 7, Text = "E2" }
+                }
+            }.AsQueryable();
+            
+            var model = new SieveModel
+            {
+                Filters = filter
+            };
+
+            var result = _processor.Apply(model, posts);
+            var entry = result.FirstOrDefault();
+            var resultCount = result.Count();
+
+            Assert.NotNull(entry);
+            Assert.Equal(1, resultCount);
+        }
+        
+        [Theory]
+        [InlineData(@"Title@=\== ")]
+        [InlineData(@"Title@=\!= ")]
+        [InlineData(@"Title@=\> ")]
+        [InlineData(@"Title@=\< ")]
+        [InlineData(@"Title@=\<= ")]
+        [InlineData(@"Title@=\>= ")]
+        [InlineData(@"Title@=\@= ")]
+        [InlineData(@"Title@=\_= ")]
+        [InlineData(@"Title@=\_-= ")]
+        [InlineData(@"Title@=!\@= ")]
+        [InlineData(@"Title@=!\_= ")]
+        [InlineData(@"Title@=!\_-= ")]
+        [InlineData(@"Title@=\@=* ")]
+        [InlineData(@"Title@=\_=* ")]
+        [InlineData(@"Title@=\_-=* ")]
+        [InlineData(@"Title@=\==* ")]
+        [InlineData(@"Title@=\!=* ")]
+        [InlineData(@"Title@=!\@=* ")]
+        public void CanFilterWithEscapedOperators(string filter)
+        {
+            var posts = new List<Post>
+            {
+                new Post
+                {
+                    Id = 1,
+                    Title = @"Operators: == != > < >= <= @= _= _-= !@= !_= !_-= @=* _=* ==* !=* !@=* !_=* !_-=* ",
+                    LikeCount = 1,
+                    IsDraft = true,
+                    CategoryId = 1,
+                    TopComment = new Comment { Id = 1, Text = "F1" },
+                    FeaturedComment = new Comment { Id = 7, Text = "F2" }
+                }
+            }.AsQueryable();
+            
+            var model = new SieveModel
+            {
+                Filters = filter,
+            };
+
+            var result = _processor.Apply(model, posts);
+            var entry = result.FirstOrDefault();
+            var resultCount = result.Count();
+
+            Assert.NotNull(entry);
+            Assert.Equal(1, resultCount);
+        }
+        
     }
 }

SieveUnitTests/Mapper.cs

@@ -2,6 +2,7 @@ using System.Collections.Generic;
 using System.Linq;
 using Sieve.Exceptions;
 using Sieve.Models;
+using Sieve.Services;
 using SieveUnitTests.Entities;
 using SieveUnitTests.Services;
 using Xunit;
@@ -10,15 +11,10 @@ namespace SieveUnitTests
 {
     public class Mapper
     {
-        private readonly ApplicationSieveProcessor _processor;
         private readonly IQueryable<Post> _posts;
 
         public Mapper()
         {
-            _processor = new ApplicationSieveProcessor(new SieveOptionsAccessor(),
-                new SieveCustomSortMethods(),
-                new SieveCustomFilterMethods());
-
             _posts = new List<Post>
             {
                 new Post
@@ -45,23 +41,49 @@ namespace SieveUnitTests
             }.AsQueryable();
         }
 
-        [Fact]
-        public void MapperWorks()
+        /// <summary>
+        /// Processors with the same mappings but configured via a different method.
+        /// </summary>
+        /// <returns></returns>
+        public static IEnumerable<object[]> GetProcessors()
+        {
+            yield return new object[] { 
+                new ApplicationSieveProcessor(
+                    new SieveOptionsAccessor(),
+                    new SieveCustomSortMethods(),
+                    new SieveCustomFilterMethods())};
+            yield return new object[] { 
+                new ModularConfigurationSieveProcessor(
+                    new SieveOptionsAccessor(),
+                    new SieveCustomSortMethods(),
+                    new SieveCustomFilterMethods())};
+            yield return new object[] { 
+                new ModularConfigurationWithScanSieveProcessor(
+                    new SieveOptionsAccessor(),
+                    new SieveCustomSortMethods(),
+                    new SieveCustomFilterMethods())};
+        }
+        
+        
+        [Theory]
+        [MemberData(nameof(GetProcessors))]
+        public void MapperWorks(ISieveProcessor processor)
         {
             var model = new SieveModel
             {
                 Filters = "shortname@=A",
             };
 
-            var result = _processor.Apply(model, _posts);
+            var result = processor.Apply(model, _posts);
 
             Assert.Equal("A", result.First().ThisHasNoAttributeButIsAccessible);
 
             Assert.True(result.Count() == 1);
         }
 
-        [Fact]
-        public void MapperSortOnlyWorks()
+        [Theory]
+        [MemberData(nameof(GetProcessors))]
+        public void MapperSortOnlyWorks(ISieveProcessor processor)
         {
             var model = new SieveModel
             {
@@ -69,9 +91,9 @@ namespace SieveUnitTests
                 Sorts = "OnlySortableViaFluentApi"
             };
 
-            var result = _processor.Apply(model, _posts, applyFiltering: false, applyPagination: false);
+            var result = processor.Apply(model, _posts, applyFiltering: false, applyPagination: false);
 
-            Assert.Throws<SieveMethodNotFoundException>(() => _processor.Apply(model, _posts));
+            Assert.Throws<SieveMethodNotFoundException>(() => processor.Apply(model, _posts));
 
             Assert.Equal(3, result.First().Id);
 

SieveUnitTests/Services/ModularConfigurationSieveProcessor.cs

@@ -0,0 +1,26 @@
+using Microsoft.Extensions.Options;
+using Sieve.Models;
+using Sieve.Services;
+using SieveUnitTests.Abstractions.Entity;
+using SieveUnitTests.Entities;
+
+namespace SieveUnitTests.Services
+{
+    public class ModularConfigurationSieveProcessor : SieveProcessor
+    {
+        public ModularConfigurationSieveProcessor(
+            IOptions<SieveOptions> options,
+            ISieveCustomSortMethods customSortMethods,
+            ISieveCustomFilterMethods customFilterMethods)
+            : base(options, customSortMethods, customFilterMethods)
+        {
+        }
+
+        protected override SievePropertyMapper MapProperties(SievePropertyMapper mapper)
+        {
+            return mapper
+                .ApplyConfiguration<SieveConfigurationForPost>()
+                .ApplyConfiguration<SieveConfigurationForIPost>();
+        }
+    }
+}

SieveUnitTests/Services/ModularConfigurationWithScanSieveProcessor.cs

@@ -0,0 +1,20 @@
+using Microsoft.Extensions.Options;
+using Sieve.Models;
+using Sieve.Services;
+
+namespace SieveUnitTests.Services
+{
+    public class ModularConfigurationWithScanSieveProcessor : SieveProcessor
+    {
+        public ModularConfigurationWithScanSieveProcessor(
+            IOptions<SieveOptions> options,
+            ISieveCustomSortMethods customSortMethods,
+            ISieveCustomFilterMethods customFilterMethods)
+            : base(options, customSortMethods, customFilterMethods)
+        {
+        }
+
+        protected override SievePropertyMapper MapProperties(SievePropertyMapper mapper) => 
+            mapper.ApplyConfigurationsFromAssembly(typeof(ModularConfigurationWithScanSieveProcessor).Assembly);
+    }
+}

SieveUnitTests/StringFilterNullTests.cs

@@ -31,14 +31,14 @@ namespace SieveUnitTests
                 {
                     Id = 1,
                     DateCreated = DateTimeOffset.UtcNow, 
-                    Text = "null is here in the text",
+                    Text = "null is here twice in the text ending by null",
                     Author = "Cat",
                 },
                 new Comment
                 {
                     Id = 2, 
                     DateCreated = DateTimeOffset.UtcNow, 
-                    Text = "Regular comment without n*ll.",
+                    Text = "Regular comment without n*ll",
                     Author = "Mouse",
                 },
                 new Comment
@@ -47,24 +47,28 @@ namespace SieveUnitTests
                     DateCreated = DateTimeOffset.UtcNow, 
                     Text = null,
                     Author = "null",
-                },
+                }
             }.AsQueryable();
         }
 
-        [Fact]
-        public void Filter_Equals_Null()
+        [Theory]
+        [InlineData("Text==null")]
+        [InlineData("Text==*null")]
+        public void Filter_Equals_Null(string filter)
         {
-            var model = new SieveModel {Filters = "Text==null"};
+            var model = new SieveModel {Filters = filter};
 
             var result = _processor.Apply(model, _comments);
 
             Assert.Equal(100, result.Single().Id);
         }
 
-        [Fact]
-        public void Filter_NotEquals_Null()
+        [Theory]
+        [InlineData("Text!=null")]
+        [InlineData("Text!=*null")]
+        public void Filter_NotEquals_Null(string filter)
         {
-            var model = new SieveModel {Filters = "Text!=null"};
+            var model = new SieveModel {Filters = filter};
 
             var result = _processor.Apply(model, _comments);
 
@@ -101,6 +105,22 @@ namespace SieveUnitTests
             Assert.Equal(expectedIds, result.Select(p => p.Id));
         }
 
+        [Theory]
+        [InlineData(@"Author==\null", 100)]
+        [InlineData(@"Author==*\null", 100)]
+        [InlineData(@"Author==*\NuLl", 100)]
+        [InlineData(@"Author!=*\null", 0, 1, 2)]
+        [InlineData(@"Author!=*\NulL", 0, 1, 2)]
+        [InlineData(@"Author!=\null", 0, 1, 2)]
+        public void SingleFilter_Equals_NullStringEscaped(string filter, params int[] expectedIds)
+        {
+            var model = new SieveModel {Filters = filter};
+
+            var result = _processor.Apply(model, _comments);
+
+            Assert.Equal(expectedIds, result.Select(p => p.Id));
+        }
+
         [Theory]
         [InlineData("Text_=null")]
         [InlineData("Text_=*null")]
@@ -116,6 +136,21 @@ namespace SieveUnitTests
             Assert.Equal(new[] {1}, result.Select(p => p.Id));
         }
 
+        [Theory]
+        [InlineData("Text_-=null")]
+        [InlineData("Text_-=*null")]
+        [InlineData("Text_-=*NULL")]
+        [InlineData("Text_-=*NulL")]
+        [InlineData("Text_-=*null|text")]
+        public void Filter_EndsWith_NullString(string filter)
+        {
+            var model = new SieveModel { Filters = filter };
+
+            var result = _processor.Apply(model, _comments);
+
+            Assert.Equal(new[] { 1 }, result.Select(p => p.Id));
+        }
+
         [Theory]
         [InlineData("Text!@=null")]
         [InlineData("Text!@=*null")]
@@ -144,5 +179,19 @@ namespace SieveUnitTests
 
             Assert.Equal(new[] {0, 2}, result.Select(p => p.Id));
         }
+
+        [Theory]
+        [InlineData("Text!_-=null")]
+        [InlineData("Text!_-=*null")]
+        [InlineData("Text!_-=*NULL")]
+        [InlineData("Text!_-=*NulL")]
+        public void Filter_DoesNotEndsWith_NullString(string filter)
+        {
+            var model = new SieveModel { Filters = filter };
+
+            var result = _processor.Apply(model, _comments);
+
+            Assert.Equal(new[] { 0, 2 }, result.Select(p => p.Id));
+        }
     }
 }