QueryHelper.cs

// ***********************************************************************
// Assembly         : FCS.Lib.Utility
// Filename         : QueryHelper.cs
// Author           : Frede Hundewadt
// Created          : 2024 03 29 12:36
// 
// Last Modified By : root
// Last Modified On : 2024 04 11 13:03
// ***********************************************************************
// <copyright company="FCS">
//     Copyright (C) 2024-2024 FCS Frede's Computer Service.
//     This program is free software: you can redistribute it and/or modify
//     it under the terms of the GNU Affero General Public License as
//     published by the Free Software Foundation, either version 3 of the
//     License, or (at your option) any later version.
// 
//     This program is distributed in the hope that it will be useful,
//     but WITHOUT ANY WARRANTY; without even the implied warranty of
//     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//     GNU Affero General Public License for more details.
// 
//     You should have received a copy of the GNU Affero General Public License
//     along with this program.  If not, see [https://www.gnu.org/licenses]
// </copyright>
// <summary></summary>
// ***********************************************************************

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


namespace FCS.Lib.Utility;

/// <summary>
///     Class QueryHelper.
/// </summary>
public static class QueryHelper
{
    // https://stackoverflow.com/a/45761590


    /// <summary>
    ///     OrderBy
    /// </summary>
    /// <param name="q"></param>
    /// <param name="name"></param>
    /// <param name="desc"></param>
    /// <typeparam name="TModel"></typeparam>
    /// <returns></returns>
    public static IQueryable<TModel> OrderBy<TModel>(this IQueryable<TModel> q, string name, bool desc)
    {
        var entityType = typeof(TModel);
        var p = entityType.GetProperty(name);
        var m = typeof(QueryHelper)
            .GetMethod("OrderByProperty")
            ?.MakeGenericMethod(entityType, p.PropertyType);

        return (IQueryable<TModel>)m.Invoke(null, new object[] { q, p, desc });
    }


    /// <summary>
    ///     ThenBy
    /// </summary>
    /// <param name="q"></param>
    /// <param name="name"></param>
    /// <param name="desc"></param>
    /// <typeparam name="TModel"></typeparam>
    /// <returns></returns>
    public static IQueryable<TModel> ThenBy<TModel>(this IQueryable<TModel> q, string name, bool desc)
    {
        var entityType = typeof(TModel);
        var p = entityType.GetProperty(name);
        var m = typeof(QueryHelper)
            .GetMethod("OrderByProperty")
            ?.MakeGenericMethod(entityType, p.PropertyType);

        return (IQueryable<TModel>)m.Invoke(null, new object[] { q, p, desc });
    }


    /// <summary>
    ///     OrderByProperty
    /// </summary>
    /// <param name="q"></param>
    /// <param name="p"></param>
    /// <param name="desc"></param>
    /// <typeparam name="TModel"></typeparam>
    /// <typeparam name="TRet"></typeparam>
    /// <returns></returns>
    public static IQueryable<TModel> OrderByProperty<TModel, TRet>(IQueryable<TModel> q, PropertyInfo p, bool desc)
    {
        var pe = Expression.Parameter(typeof(TModel));
        Expression se = Expression.Convert(Expression.Property(pe, p), typeof(object));
        var exp = Expression.Lambda<Func<TModel, TRet>>(se, pe);

        return desc ? q.OrderByDescending(exp) : q.OrderBy(exp);
    }
}