ERP/TradeUsedSale/Repositories/Utils/QueryableExtensions.cs

using System;
using System.Linq;
using System.Linq.Expressions;

namespace TradeUsedSale.Repositories.Utils
{
    public static class QueryableExtensions
    {
        /// <summary>
        /// Used for paging. Can be used as an alternative to Skip(...).Take(...) chaining.
        /// </summary>
        public static IQueryable<T> PageBy<T>(this IQueryable<T> query, int skipCount, int maxResultCount)
        {
            return query.Skip(skipCount).Take(maxResultCount);
        }

        /// <summary>
        /// Used for paging. Can be used as an alternative to Skip(...).Take(...) chaining.
        /// </summary>
        public static TQueryable PageBy<T, TQueryable>(this TQueryable query, int skipCount, int maxResultCount)
            where TQueryable : IQueryable<T>
        {
            return (TQueryable)query.Skip(skipCount).Take(maxResultCount);
        }

        /// <summary>
        /// Filters a <see cref="IQueryable{T}"/> by given predicate if given condition is true.
        /// </summary>
        /// <param name="query">Queryable to apply filtering</param>
        /// <param name="condition">A boolean value</param>
        /// <param name="predicate">Predicate to filter the query</param>
        /// <returns>Filtered or not filtered query based on <paramref name="condition"/></returns>
        public static IQueryable<T> WhereIf<T>(this IQueryable<T> query, bool condition,
            Expression<Func<T, bool>> predicate)
        {
            return condition
                ? query.Where(predicate)
                : query;
        }

        /// <summary>
        /// Filters a <see cref="IQueryable{T}"/> by given predicate if given condition is true.
        /// </summary>
        /// <param name="query">Queryable to apply filtering</param>
        /// <param name="condition">A boolean value</param>
        /// <param name="predicate">Predicate to filter the query</param>
        /// <returns>Filtered or not filtered query based on <paramref name="condition"/></returns>
        public static TQueryable WhereIf<T, TQueryable>(this TQueryable query, bool condition,
            Expression<Func<T, bool>> predicate)
            where TQueryable : IQueryable<T>
        {
            return condition
                ? (TQueryable)query.Where(predicate)
                : query;
        }

        /// <summary>
        /// Filters a <see cref="IQueryable{T}"/> by given predicate if given condition is true.
        /// </summary>
        /// <param name="query">Queryable to apply filtering</param>
        /// <param name="condition">A boolean value</param>
        /// <param name="predicate">Predicate to filter the query</param>
        /// <returns>Filtered or not filtered query based on <paramref name="condition"/></returns>
        public static IQueryable<T> WhereIf<T>(this IQueryable<T> query, bool condition,
            Expression<Func<T, int, bool>> predicate)
        {
            return condition
                ? query.Where(predicate)
                : query;
        }

        /// <summary>
        /// Filters a <see cref="IQueryable{T}"/> by given predicate if given condition is true.
        /// </summary>
        /// <param name="query">Queryable to apply filtering</param>
        /// <param name="condition">A boolean value</param>
        /// <param name="predicate">Predicate to filter the query</param>
        /// <returns>Filtered or not filtered query based on <paramref name="condition"/></returns>
        public static TQueryable WhereIf<T, TQueryable>(this TQueryable query, bool condition,
            Expression<Func<T, int, bool>> predicate)
            where TQueryable : IQueryable<T>
        {
            return condition
                ? (TQueryable)query.Where(predicate)
                : query;
        }
    }
}