SieveProcessor.cs

using System;
using System.ComponentModel;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using Microsoft.Extensions.Options;
using Sieve.Attributes;
using Sieve.Exceptions;
using Sieve.Extensions;
using Sieve.Models;

namespace Sieve.Services
{
    public class SieveProcessor : SieveProcessor<SieveModel, FilterTerm, SortTerm>, ISieveProcessor
    {
        public SieveProcessor(IOptions<SieveOptions> options) : base(options)
        {
        }

        public SieveProcessor(IOptions<SieveOptions> options, ISieveCustomSortMethods customSortMethods) : base(options, customSortMethods)
        {
        }

        public SieveProcessor(IOptions<SieveOptions> options, ISieveCustomFilterMethods customFilterMethods) : base(options, customFilterMethods)
        {
        }

        public SieveProcessor(IOptions<SieveOptions> options, ISieveCustomSortMethods customSortMethods, ISieveCustomFilterMethods customFilterMethods) : base(options, customSortMethods, customFilterMethods)
        {
        }
    }

    public class SieveProcessor<TFilterTerm, TSortTerm> : SieveProcessor<SieveModel<TFilterTerm, TSortTerm>, TFilterTerm, TSortTerm>, ISieveProcessor<TFilterTerm, TSortTerm>
        where TFilterTerm : IFilterTerm, new()
        where TSortTerm : ISortTerm, new()
    {
        public SieveProcessor(IOptions<SieveOptions> options) : base(options)
        {
        }

        public SieveProcessor(IOptions<SieveOptions> options, ISieveCustomSortMethods customSortMethods) : base(options, customSortMethods)
        {
        }

        public SieveProcessor(IOptions<SieveOptions> options, ISieveCustomFilterMethods customFilterMethods) : base(options, customFilterMethods)
        {
        }

        public SieveProcessor(IOptions<SieveOptions> options, ISieveCustomSortMethods customSortMethods, ISieveCustomFilterMethods customFilterMethods) : base(options, customSortMethods, customFilterMethods)
        {
        }
    }

    public class SieveProcessor<TSieveModel, TFilterTerm, TSortTerm> : ISieveProcessor<TSieveModel, TFilterTerm, TSortTerm>
        where TSieveModel : class, ISieveModel<TFilterTerm, TSortTerm>
        where TFilterTerm : IFilterTerm, new()
        where TSortTerm : ISortTerm, new()
    {
        private readonly IOptions<SieveOptions> _options;
        private readonly ISieveCustomSortMethods _customSortMethods;
        private readonly ISieveCustomFilterMethods _customFilterMethods;
        private readonly SievePropertyMapper mapper = new SievePropertyMapper();

        public SieveProcessor(IOptions<SieveOptions> options,
            ISieveCustomSortMethods customSortMethods,
            ISieveCustomFilterMethods customFilterMethods)
        {
            mapper = MapProperties(mapper);
            _options = options;
            _customSortMethods = customSortMethods;
            _customFilterMethods = customFilterMethods;
        }

        public SieveProcessor(IOptions<SieveOptions> options,
            ISieveCustomSortMethods customSortMethods)
        {
            mapper = MapProperties(mapper);
            _options = options;
            _customSortMethods = customSortMethods;
        }

        public SieveProcessor(IOptions<SieveOptions> options,
            ISieveCustomFilterMethods customFilterMethods)
        {
            mapper = MapProperties(mapper);
            _options = options;
            _customFilterMethods = customFilterMethods;
        }

        public SieveProcessor(IOptions<SieveOptions> options)
        {
            mapper = MapProperties(mapper);
            _options = options;
        }

        /// <summary>
        /// Apply filtering, sorting, and pagination parameters found in `model` to `source`
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <param name="model">An instance of ISieveModel</param>
        /// <param name="source">Data source</param>
        /// <param name="dataForCustomMethods">Additional data that will be passed down to custom methods</param>
        /// <param name="applyFiltering">Should the data be filtered? Defaults to true.</param>
        /// <param name="applySorting">Should the data be sorted? Defaults to true.</param>
        /// <param name="applyPagination">Should the data be paginated? Defaults to true.</param>
        /// <returns>Returns a transformed version of `source`</returns>
        public IQueryable<TEntity> Apply<TEntity>(
            TSieveModel model,
            IQueryable<TEntity> source,
            object[] dataForCustomMethods = null,
            bool applyFiltering = true,
            bool applySorting = true,
            bool applyPagination = true)
        {
            var result = source;

            if (model == null)
            {
                return result;
            }

            try
            {
                // Filter
                if (applyFiltering)
                {
                    result = ApplyFiltering(model, result, dataForCustomMethods);
                }

                // Sort
                if (applySorting)
                {
                    result = ApplySorting(model, result, dataForCustomMethods);
                }

                // Paginate
                if (applyPagination)
                {
                    result = ApplyPagination(model, result);
                }

                return result;
            }
            catch (Exception ex)
            {
                if (_options.Value.ThrowExceptions)
                {
                    if (ex is SieveException)
                    {
                        throw;
                    }

                    throw new SieveException(ex.Message, ex);
                }
                else
                {
                    return result;
                }
            }
        }

        public string GetExtendFilterString<TEntity>(
          TSieveModel model, 
          bool bCaseSensitive = false)
        {
            string fullQueryString = "";
            //string dynamicQuery = "";
            if (model?.GetFiltersParsed() == null)
            {
                return " id != null";
            }

            //Expression outerExpression = null;
            //var parameterExpression = Expression.Parameter(typeof(TEntity), "e");
            foreach (var filterTerm in model.GetFiltersParsed())
            {
               
                //Expression innerExpression = null;
                foreach (var filterTermName in filterTerm.Names)
                {
                    string searchPart = "";

                    string searchProperty = ""; ////////-----------------
                    var (fullName, property) = GetSieveProperty<TEntity>(false, true, filterTermName);
                    if (property != null)
                    {
                        var converter = TypeDescriptor.GetConverter(property.PropertyType);
                        //dynamic propertyValue = parameterExpression;
                        foreach (object attrib in property.GetCustomAttributes(true))
                        {
                            searchProperty = attrib.GetType().GetProperty("StringValue").GetValue(attrib, null).ToString();                           
                        }
                        //foreach (var part in fullName.Split('.'))
                        //{
                        //    propertyValue = Expression.PropertyOrField(propertyValue, part);
                        //}

                        if (filterTerm.Values == null) continue;

                        foreach (var filterTermValue in filterTerm.Values)
                        {
                            string dynamicQuery = ""; //////----------------
                            dynamic constantVal = converter.CanConvertFrom(typeof(string))
                                                      ? converter.ConvertFrom(filterTermValue)
                                                      : Convert.ChangeType(filterTermValue, property.PropertyType);

                            Expression filterValue = GetClosureOverConstant(constantVal, property.PropertyType);

                            if (!string.IsNullOrEmpty(searchProperty))
                            {
                                var data = RemoveSignAndLowerCase4VietnameseString(filterValue.ToString());
                                dynamicQuery = GetDynamicQueryString(filterTerm, searchProperty.ToString(), data);
                                if (string.IsNullOrEmpty(fullQueryString))
                                {
                                    searchPart = "(" + dynamicQuery + ")";
                                }
                                else
                                {
                                    searchPart += " Or " + "(" + dynamicQuery + ")";
                                }
                            }

                            #region advance
                            //if (filterTerm.OperatorIsCaseInsensitive)
                            //{
                            //    propertyValue = Expression.Call(propertyValue,
                            //        typeof(string).GetMethods()
                            //        .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, bCaseSensitive);

                            //if (filterTerm.OperatorIsNegated)
                            //{
                            //    expression = Expression.Not(expression);
                            //}

                            //if (innerExpression == null)
                            //{
                            //    innerExpression = expression;
                            //}
                            //else
                            //{
                            //    innerExpression = Expression.Or(innerExpression, expression);
                            //}
                            #endregion

                        }
                    }

                    if (!string.IsNullOrEmpty(searchPart))
                    {
                        if (string.IsNullOrEmpty(fullQueryString))
                        {
                            fullQueryString = "(" + searchPart + ")";
                        }
                        else
                        {
                            fullQueryString += " And " + "(" + searchPart + ")";
                        }
                    }

                }
            }
            if (string.IsNullOrEmpty(fullQueryString))
            {
                fullQueryString = " id != null";
            }
            return  fullQueryString ;
        }

        protected object ChangeType(object value, Type conversion)
        {
            var t = conversion;

            if (t.IsGenericType && t.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
            {
                if (value == null)
                {
                    return null;
                }

                t = Nullable.GetUnderlyingType(t);
            }            
            return Convert.ChangeType(value, t);
        }
        public Expression<Func<TEntity, bool>> GetFilterExpressionQuery<TEntity>(
           TSieveModel model,
           bool bCaseSensitive = false)
        {
            Expression outerExpression = null;
            var parameterExpression = Expression.Parameter(typeof(TEntity), "e");
            //string dynamicQuery = "";
            if (model?.GetFiltersParsed() == null)
            {
                var property = Expression.Property(parameterExpression, "id");
                ConstantExpression constant = Expression.Constant(new Guid("{00000000-0000-0000-0000-000000000000}"), typeof(Guid));
                var rst = Expression.NotEqual(property, constant);

                return Expression.Lambda<Func<TEntity, bool>>(rst, parameterExpression);
            }

          
            foreach (var filterTerm in model.GetFiltersParsed())
            {
                Expression innerExpression = null;
                foreach (var filterTermName in filterTerm.Names)
                {
                    var (fullName, property) = GetSieveProperty<TEntity>(false, true, filterTermName);
                    if (property != null)
                    {
                        var converter = TypeDescriptor.GetConverter(property.PropertyType);

                        dynamic propertyValue = parameterExpression;
                     
                        foreach (var part in fullName.Split('.'))
                        {
                            propertyValue = Expression.PropertyOrField(propertyValue, part);
                        }

                        if (filterTerm.Values == null) continue;

                        foreach (var filterTermValue in filterTerm.Values)
                        {

                            dynamic constantVal = converter.CanConvertFrom(typeof(string))
                                                      ? converter.ConvertFrom(filterTermValue)
                                                      : Convert.ChangeType(filterTermValue, property.PropertyType);

                            Expression filterValue = GetClosureOverConstant(constantVal, property.PropertyType);

                           
                            if (filterTerm.OperatorIsCaseInsensitive)
                            {
                                propertyValue = Expression.Call(propertyValue,
                                    typeof(string).GetMethods()
                                    .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, bCaseSensitive);

                            if (filterTerm.OperatorIsNegated)
                            {
                                expression = Expression.Not(expression);
                            }

                            if (innerExpression == null)
                            {
                                innerExpression = expression;
                            }
                            else
                            {
                                innerExpression = Expression.Or(innerExpression, expression);
                            }
                        }
                    }

                }
                if (outerExpression == null)
                {
                    outerExpression = innerExpression;
                    continue;
                }
                if (innerExpression == null)
                {
                    continue;
                }
                outerExpression = Expression.And(outerExpression, innerExpression);
            }
            if (outerExpression == null)
            {
                var property = Expression.Property(parameterExpression, "id");
                ConstantExpression constant = Expression.Constant(new Guid("{00000000-0000-0000-0000-000000000000}"), typeof(Guid));
                var rst = Expression.NotEqual(property, constant);
                return Expression.Lambda<Func<TEntity, bool>>(rst, parameterExpression);
            }
            return Expression.Lambda<Func<TEntity, bool>>(outerExpression, parameterExpression);
        }

       
        private IQueryable<TEntity> ApplyFiltering<TEntity>(
            TSieveModel model,
            IQueryable<TEntity> result,
            object[] dataForCustomMethods = null,
            bool bCaseSensitive = false)
        {
            if (model?.GetFiltersParsed() == null)
            {
                return result;
            }

            Expression outerExpression = null;
            var parameterExpression = Expression.Parameter(typeof(TEntity), "e");
            foreach (var filterTerm in model.GetFiltersParsed())
            {
                Expression innerExpression = null;
                foreach (var filterTermName in filterTerm.Names)
                {
                    var (fullName, property) = GetSieveProperty<TEntity>(false, true, filterTermName);
                    if (property != null)
                    {
                        var converter = TypeDescriptor.GetConverter(property.PropertyType);

                        dynamic propertyValue = parameterExpression;
                        foreach (var part in fullName.Split('.'))
                        {
                            propertyValue = Expression.PropertyOrField(propertyValue, part);
                        }

                        if (filterTerm.Values == null) continue;

                        foreach (var filterTermValue1 in filterTerm.Values)
                        {
                            var filterTermValue = (new RemoveVietNamSign()).RemoveSignVietnameseString(filterTermValue1);
                            //string filterTermValue = this.RemoveSign4VietnameseString(filterTermValue1); //Added by thien to emove vietnam

                            dynamic constantVal = converter.CanConvertFrom(typeof(string))
                                                      ? converter.ConvertFrom(filterTermValue)
                                                      : Convert.ChangeType(filterTermValue, property.PropertyType);

                            Expression filterValue = GetClosureOverConstant(constantVal, property.PropertyType);


                            if (true)//filterTerm.OperatorIsCaseInsensitive Make search insensitive case //comment by thien
                            {
                                var upperData = Expression.Call(propertyValue,
                                    typeof(string).GetMethods()
                                    .First(m => m.Name == "ToUpper" && m.GetParameters().Length == 0));
                                propertyValue = Expression.Call(
                                Expression.New(typeof(RemoveVietNamSign)),
                                typeof(RemoveVietNamSign).GetMethod("RemoveSignVietnameseString", new Type[] { typeof(string)}),
                                upperData
                                );

                                /*propertyValue = Expression.Call(propertyValue,
                                    typeof(string).GetMethods()
                                    .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, bCaseSensitive);

                            if (filterTerm.OperatorIsNegated)
                            {
                                expression = Expression.Not(expression);
                            }

                            if (innerExpression == null)
                            {
                                innerExpression = expression;
                            }
                            else
                            {
                                innerExpression = Expression.Or(innerExpression, expression);
                            }
                        }
                    }
                    else
                    {
                        result = ApplyCustomMethod(result, filterTermName, _customFilterMethods,
                            new object[] {
                                            result,
                                            filterTerm.Operator,
                                            filterTerm.Values
                            }, dataForCustomMethods);

                    }
                }
                if (outerExpression == null)
                {
                    outerExpression = innerExpression;
                    continue;
                }
                if (innerExpression == null)
                {
                    continue;
                }
                outerExpression = Expression.And(outerExpression, innerExpression);
            }
            
            var data = outerExpression == null
                ? result
                : result.Where(Expression.Lambda<Func<TEntity, bool>>(outerExpression, parameterExpression));
            return data;
        }
        private static string GetDynamicQueryString(TFilterTerm filterTerm, string property, string value)
        {
            string sResult = property;
            switch (filterTerm.OperatorParsed)
            {
                case FilterOperator.Equals:
                    return sResult + "=" + value;
                case FilterOperator.NotEquals:
                    return sResult + "!=" + value;
                case FilterOperator.GreaterThan:
                    return sResult + ">" + value;
                case FilterOperator.LessThan:
                    return sResult + "<" + value;
                case FilterOperator.GreaterThanOrEqualTo:
                    return sResult + ">=" + value;
                case FilterOperator.LessThanOrEqualTo:
                    return sResult + "<=" + value;
                case FilterOperator.Contains:
                    return sResult + ".Contains(" + value + ")";
                case FilterOperator.StartsWith:
                    return sResult + ".Contains(" + value + ")";
                default:
                    return sResult + "=" + value;
            }
        }

        
            private static string[] VietnameseSigns = new string[]
            {

            "aAeEoOuUiIdDyY",

            "áàạảãâấầậẩẫăắằặẳẵ",

            "ÁÀẠẢÃÂẤẦẬẨẪĂẮẰẶẲẴ",

            "éèẹẻẽêếềệểễ",

            "ÉÈẸẺẼÊẾỀỆỂỄ",

            "óòọỏõôốồộổỗơớờợởỡ",

            "ÓÒỌỎÕÔỐỒỘỔỖƠỚỜỢỞỠ",

            "úùụủũưứừựửữ",

            "ÚÙỤỦŨƯỨỪỰỬỮ",

            "íìịỉĩ",

            "ÍÌỊỈĨ",

            "đ",

            "Đ",

            "ýỳỵỷỹ",

            "ÝỲỴỶỸ"
            };
            public static string RemoveSignAndLowerCase4VietnameseString(string str)
            {
                str = str.ToLower();
                for (int i = 1; i < VietnameseSigns.Length; i++)
                {
                    for (int j = 0; j < VietnameseSigns[i].Length; j++)
                        str = str.Replace(VietnameseSigns[i][j], VietnameseSigns[0][i - 1]);
                }
                return str;
            }
            private static Expression GetExpression(TFilterTerm filterTerm, dynamic filterValue, dynamic propertyValue, bool bCaseSensitive)
        {
            switch (filterTerm.OperatorParsed)
            {
                case FilterOperator.Equals:
                    return Expression.Equal(propertyValue, filterValue);
                case FilterOperator.NotEquals:
                    return Expression.NotEqual(propertyValue, filterValue);
                case FilterOperator.GreaterThan:
                    return Expression.GreaterThan(propertyValue, filterValue);
                case FilterOperator.LessThan:
                    return Expression.LessThan(propertyValue, filterValue);
                case FilterOperator.GreaterThanOrEqualTo:
                    return Expression.GreaterThanOrEqual(propertyValue, filterValue);
                case FilterOperator.LessThanOrEqualTo:
                    return Expression.LessThanOrEqual(propertyValue, filterValue);
                case FilterOperator.Contains:
                    //fixed bug has null in data
                    return Expression.AndAlso(Expression.NotEqual(propertyValue, Expression.Constant(null, typeof(object))), Expression.Call(propertyValue,
                        typeof(string).GetMethods()
                        .First(m => m.Name == "Contains" && m.GetParameters().Length == 1),
                        filterValue));
                case FilterOperator.StartsWith:
                    return Expression.AndAlso(Expression.NotEqual(propertyValue, Expression.Constant(null, typeof(object))), Expression.Call(propertyValue,
                        typeof(string).GetMethods()
                        .First(m => m.Name == "StartsWith" && m.GetParameters().Length == 1),
                        filterValue));
                default:
                    return Expression.Equal(propertyValue, filterValue);
            }
        }

        // Workaround to ensure that the filter value gets passed as a parameter in generated SQL from EF Core
        // See https://github.com/aspnet/EntityFrameworkCore/issues/3361
        // Expression.Constant passed the target type to allow Nullable comparison
        // See http://bradwilson.typepad.com/blog/2008/07/creating-nullab.html
        private Expression GetClosureOverConstant<T>(T constant, Type targetType)
        {
            return Expression.Constant(constant, targetType);
        }

        private IQueryable<TEntity> ApplySorting<TEntity>(
            TSieveModel model,
            IQueryable<TEntity> result,
            object[] dataForCustomMethods = null)
        {
            if (model?.GetSortsParsed() == null)
            {
                return result;
            }

            var useThenBy = false;
            foreach (var sortTerm in model.GetSortsParsed())
            {
                var (fullName, property) = GetSieveProperty<TEntity>(true, false, sortTerm.Name);

                if (property != null)
                {
                    result = result.OrderByDynamic(fullName, property, sortTerm.Descending, useThenBy);
                }
                else
                {
                    result = ApplyCustomMethod(result, sortTerm.Name, _customSortMethods,
                        new object[]
                        {
                            result,
                            useThenBy,
                            sortTerm.Descending
                        }, dataForCustomMethods);
                }
                useThenBy = true;
            }

            return result;
        }
        public int ResultCountBeForeApplyPagination = 0;
        public void GetSkipAndTake( TSieveModel model, ref int skip, ref int take)
        {
            var page = model?.Page ?? 1;
            var pageSize = model?.PageSize ?? _options.Value.DefaultPageSize;
            var maxPageSize = _options.Value.MaxPageSize > 0 ? _options.Value.MaxPageSize : pageSize;
            skip = (page - 1) * pageSize;
            take = Math.Min(pageSize, maxPageSize);
        }
        public bool applyPageSize = true;
        private IQueryable<TEntity> ApplyPagination<TEntity>(
            TSieveModel model,
            IQueryable<TEntity> result)
        {            
            var page = model?.Page ?? 1;
            model.Page = page;
            var pageSize = model?.PageSize ?? _options.Value.DefaultPageSize;
            model.PageSize = pageSize;
            var maxPageSize = _options.Value.MaxPageSize > 0 ? _options.Value.MaxPageSize : pageSize;
            if (ResultCountBeForeApplyPagination==0)
            {
                try
                {
                    ResultCountBeForeApplyPagination = result != null ? result.Count() : 0;
                }
                catch (Exception)
                {
                    ResultCountBeForeApplyPagination = 0;
                }
               
            }
            
            if (pageSize > 0)
            {
                if (applyPageSize)
                {
                    result = result.Skip((page - 1) * pageSize);
                    result = result.Take(Math.Min(pageSize, maxPageSize));
                }                
            }

            return result;
        }

        protected virtual SievePropertyMapper MapProperties(SievePropertyMapper mapper)
        {
            return mapper;
        }

        private (string, PropertyInfo) GetSieveProperty<TEntity>(
            bool canSortRequired,
            bool canFilterRequired,
            string name)
        {
            var property = mapper.FindProperty<TEntity>(canSortRequired, canFilterRequired, name, _options.Value.CaseSensitive);
            if (property.Item1 == null)
            {
                var prop = FindPropertyBySieveAttribute<TEntity>(canSortRequired, canFilterRequired, name, _options.Value.CaseSensitive);
                return (prop?.Name, prop);
            }
            return property;

        }

        private PropertyInfo FindPropertyBySieveAttribute<TEntity>(
            bool canSortRequired,
            bool canFilterRequired,
            string name,
            bool isCaseSensitive)
        {
            return Array.Find(typeof(TEntity).GetProperties(), p =>
                {
                    if (p.GetCustomAttribute(typeof(SieveAttribute)) is SieveAttribute)
                    {
                        return p.GetCustomAttribute(typeof(SieveAttribute)) is SieveAttribute sieveAttribute
                        && (canSortRequired ? sieveAttribute.CanSort : true)
                        && (canFilterRequired ? sieveAttribute.CanFilter : true)
                        && ((sieveAttribute.Name ?? p.Name).Equals(name, isCaseSensitive ? StringComparison.Ordinal : StringComparison.OrdinalIgnoreCase));
                    }
                    else
                    {
                        return (p.Name).Equals(name, isCaseSensitive ? StringComparison.Ordinal : StringComparison.OrdinalIgnoreCase);
                    }
                   

                    /*Comment by thien vo to apply sort/filter by all property
                    return p.GetCustomAttribute(typeof(SieveAttribute)) is SieveAttribute sieveAttribute
                    && (canSortRequired ? sieveAttribute.CanSort : true)
                    && (canFilterRequired ? sieveAttribute.CanFilter : true)
                    && ((sieveAttribute.Name ?? p.Name).Equals(name, isCaseSensitive ? StringComparison.Ordinal : StringComparison.OrdinalIgnoreCase));
                      */
                });
        }

        private IQueryable<TEntity> ApplyCustomMethod<TEntity>(IQueryable<TEntity> result, string name, object parent, object[] parameters, object[] optionalParameters = null)
        {
            var customMethod = parent?.GetType()
                .GetMethodExt(name,
                _options.Value.CaseSensitive ? BindingFlags.Default : BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance,
                typeof(IQueryable<TEntity>));


            if (customMethod == null)
            {
                // Find generic methods `public IQueryable<T> Filter<T>(IQueryable<T> source, ...)`
                var genericCustomMethod = parent?.GetType()
                .GetMethodExt(name,
                _options.Value.CaseSensitive ? BindingFlags.Default : BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance,
                typeof(IQueryable<>));

                if (genericCustomMethod != null &&
                    genericCustomMethod.ReturnType.IsGenericType &&
                    genericCustomMethod.ReturnType.GetGenericTypeDefinition() == typeof(IQueryable<>))
                {
                    var genericBaseType = genericCustomMethod.ReturnType.GenericTypeArguments[0];
                    var constraints = genericBaseType.GetGenericParameterConstraints();
                    if (constraints == null || constraints.Length == 0 || constraints.All((t) => t.IsAssignableFrom(typeof(TEntity))))
                    {
                        customMethod = genericCustomMethod.MakeGenericMethod(typeof(TEntity));
                    }
                }
            }

            if (customMethod != null)
            {
                try
                {
                    result = customMethod.Invoke(parent, parameters)
                        as IQueryable<TEntity>;
                }
                catch (TargetParameterCountException)
                {
                    if (optionalParameters != null)
                    {
                        result = customMethod.Invoke(parent, parameters.Concat(optionalParameters).ToArray())
                            as IQueryable<TEntity>;
                    }
                    else
                    {
                        throw;
                    }
                }
            }
            else
            {
                var incompatibleCustomMethod = parent?.GetType()
                    .GetMethod(name,
                    _options.Value.CaseSensitive ? BindingFlags.Default : BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance);

                if (incompatibleCustomMethod != null)
                {
                    var expected = typeof(IQueryable<TEntity>);
                    var actual = incompatibleCustomMethod.ReturnType;
                    throw new SieveIncompatibleMethodException(name, expected, actual,
                        $"{name} failed. Expected a custom method for type {expected} but only found for type {actual}");
                }
                else
                {
                    throw new SieveMethodNotFoundException(name, $"{name} not found.");
                }
            }

            return result;
        }
    }
}