Bagaimana saya boleh melakukan pesanan linq dinamik pada kedua -dua `ienumerable` dan` iQueryable`?

Dynamic Linq Orderby pada iEnumerable & lt; t & gt; / IQueryable & lt; t & gt;

Dynamic Linq menyediakan cara yang mudah untuk memerintahkan data menggunakan rentetan seperti SQL. Walau bagaimanapun, contoh dalam contoh Visual Studio 2008 hanya berfungsi pada iQueryable & lt; t & gt;.

Jika anda ingin menggunakan fungsi ini untuk iEnumerable & lt; t & gt;, anda boleh menggunakan kod berikut:

public static IOrderedQueryable<t> OrderBy<t>(
    this IQueryable<t> source, 
    string property)
{
    return ApplyOrder<t>(source, property, "OrderBy");
}

public static IOrderedQueryable<t> OrderByDescending<t>(
    this IQueryable<t> source, 
    string property)
{
    return ApplyOrder<t>(source, property, "OrderByDescending");
}

public static IOrderedQueryable<t> ThenBy<t>(
    this IOrderedQueryable<t> source, 
    string property)
{
    return ApplyOrder<t>(source, property, "ThenBy");
}

public static IOrderedQueryable<t> ThenByDescending<t>(
    this IOrderedQueryable<t> source, 
    string property)
{
    return ApplyOrder<t>(source, property, "ThenByDescending");
}

static IOrderedQueryable<t> ApplyOrder<t>(
    IQueryable<t> source, 
    string property, 
    string methodName) 
{
    string[] props = property.Split('.');
    Type type = typeof(T);
    ParameterExpression arg = Expression.Parameter(type, "x");
    Expression expr = arg;
    foreach(string prop in props) {
        // use reflection (not ComponentModel) to mirror LINQ
        PropertyInfo pi = type.GetProperty(prop);
        expr = Expression.Property(expr, pi);
        type = pi.PropertyType;
    }
    Type delegateType = typeof(Func).MakeGenericType(typeof(T), type);
    LambdaExpression lambda = Expression.Lambda(delegateType, expr, arg);

    object result = typeof(Queryable).GetMethods().Single(
            method => method.Name == methodName
                    && method.IsGenericMethodDefinition
                    && method.GetGenericArguments().Length == 2
                    && method.GetParameters().Length == 2)
            .MakeGenericMethod(typeof(T), type)
            .Invoke(null, new object[] {source, lambda});
    return (IOrderedQueryable<t>)result;
}</t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t></t>

untuk menggunakan kod ini dengan objek dinamik, anda boleh menggunakan yang berikut Kod:

using Microsoft.CSharp.RuntimeBinder;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Dynamic;
using System.Linq;
using System.Runtime.CompilerServices;
static class Program
{
    private static class AccessorCache
    {
        private static readonly Hashtable accessors = new Hashtable();

        private static readonly Hashtable callSites = new Hashtable();

        private static CallSite<func object>> GetCallSiteLocked(
            string name) 
        {
            var callSite = (CallSite<func object>>)callSites[name];
            if(callSite == null)
            {
                callSites[name] = callSite = CallSite<func object>>
                    .Create(Binder.GetMember(
                                CSharpBinderFlags.None, 
                                name, 
                                typeof(AccessorCache),
                                new CSharpArgumentInfo[] { 
                                    CSharpArgumentInfo.Create(
                                        CSharpArgumentInfoFlags.None, 
                                        null) 
                                }));
            }
            return callSite;
        }

        internal static Func<dynamic> GetAccessor(string name)
        {
            Func<dynamic object> accessor = (Func<dynamic object>)accessors[name];
            if (accessor == null)
            {
                lock (accessors )
                {
                    accessor = (Func<dynamic object>)accessors[name];
                    if (accessor == null)
                    {
                        if(name.IndexOf('.') >= 0) {
                            string[] props = name.Split('.');
                            CallSite<func object>>[] arr 
                                = Array.ConvertAll(props, GetCallSiteLocked);
                            accessor = target =>
                            {
                                object val = (object)target;
                                for (int i = 0; i 
                            {
                                return callSite.Target(callSite, (object)target);
                            };
                        }
                        accessors[name] = accessor;
                    }
                }
            }
            return accessor;
        }
    }

    public static IOrderedEnumerable<dynamic> OrderBy(
        this IEnumerable<dynamic> source, 
        string property)
    {
        return Enumerable.OrderBy<dynamic object>(
            source, 
            AccessorCache.GetAccessor(property), 
            Comparer<object>.Default);
    }

    public static IOrderedEnumerable<dynamic> OrderByDescending(
        this IEnumerable<dynamic> source, 
        string property)
    {
        return Enumerable.OrderByDescending<dynamic object>(
            source, 
            AccessorCache.GetAccessor(property), 
            Comparer<object>.Default);
    }

    public static IOrderedEnumerable<dynamic> ThenBy(
        this IOrderedEnumerable<dynamic> source, 
        string property)
    {
        return Enumerable.ThenBy<dynamic object>(
            source, 
            AccessorCache.GetAccessor(property), 
            Comparer<object>.Default);
    }

    public static IOrderedEnumerable<dynamic> ThenByDescending(
        this IOrderedEnumerable<dynamic> source, 
        string property)
    {
        return Enumerable.ThenByDescending<dynamic object>(
            source, 
            AccessorCache.GetAccessor(property), 
            Comparer<object>.Default);
    }

    static void Main()
    {
        dynamic a = new ExpandoObject(), 
                b = new ExpandoObject(), 
                c = new ExpandoObject();
        a.X = "abc";
        b.X = "ghi";
        c.X = "def";
        dynamic[] data = new[] { 
            new { Y = a },
            new { Y = b }, 
            new { Y = c } 
        };

        var ordered = data.OrderByDescending("Y.X").ToArray();
        foreach (var obj in ordered)
        {
            Console.WriteLine(obj.Y.X);
        }
    }
}</object></dynamic></dynamic></dynamic></object></dynamic></dynamic></dynamic></object></dynamic></dynamic></dynamic></object></dynamic></dynamic></dynamic></func></dynamic></dynamic></dynamic></dynamic></func></func></func>

Atas ialah kandungan terperinci Bagaimana saya boleh melakukan pesanan linq dinamik pada kedua -dua `ienumerable` dan` iQueryable`?. Untuk maklumat lanjut, sila ikut artikel berkaitan lain di laman web China PHP!