abp boilerplate deki QueryableExtensions.cs dosyasına orderby if eklenmiş hali. kısaca kodun işlevi verilen şart geçerli ise where kosulunu queryable ekliyor.

QueryableExtensions

using System;
using System.Linq;
using System.Linq.Expressions;
using System.ServiceModel.Channels;

namespace KYGM.Framework.Core.Utilities.Helpers
{
    /// <summary>
    /// Some useful extension methods for <see cref="IQueryable{T}"/>.
    /// </summary>
    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)
        {
            if (query == null)
            {
                throw new ArgumentNullException(nameof(query));
            }

            return 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 IQueryable<T> WhereIf<T>(this IQueryable<T> query, bool condition, Expression<Func<T, int, bool>> predicate)
        {
            return condition
                ? query.Where(predicate)
                : query;
        }
        public static IQueryable<TSource> OrderByIf<TSource, TKey>(this IQueryable<TSource> query, bool condition, string sortTypeName, Expression<Func<TSource, TKey>> orderByExpression)
        {
            return query.OrderByIf(condition, sortTypeName == "asc", orderByExpression);
        }
        
        public static IQueryable<TSource> OrderByIf<TSource, TKey>(this IQueryable<TSource> query, bool condition, bool isAsc, Expression<Func<TSource, TKey>> orderByExpression)
        {
            if (condition)
            {
                return isAsc ? query.OrderBy(orderByExpression) : query.OrderByDescending(orderByExpression);
            }
            return query;
        }
    }
}