错误是

LINQ to Entities does not recognize the method 'System.Object GetValue(System.Object, System.Object[])' method, and this method cannot be translated into a store expression.

我的代码是

public static GridResult GetAllUsers(int count, int tblsize,string sortcreteria)
{
      using (UserEntities entity = new UserEntities())
      {

          var data = entity.User_Details.Take(count)
.OrderBy(i =>.GetType().GetProperty(sortcreteria).GetValue(i,null))
.Skip(tblsize).ToList();
          result.DataSource = data;
          result.Count = entity.User_Details.Count();
      }
      return result;
}

如何将属性名作为字符串进行排序？

最佳答案

只需将以下扩展添加到您的代码中即可:

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

namespace SomeNameSpace
{
    public static class SomeExtensionClass
    {
        public static IQueryable<T> OrderByField<T>(this IQueryable<T> q, string SortField, bool Ascending)
        {
            var param = Expression.Parameter(typeof(T), "p");
            var prop = Expression.Property(param, SortField);
            var exp = Expression.Lambda(prop, param);
            string method = Ascending ? "OrderBy" : "OrderByDescending";
            Type[] types = new Type[] { q.ElementType, exp.Body.Type };
            var mce = Expression.Call(typeof(Queryable), method, types, q.Expression, exp);
            return q.Provider.CreateQuery<T>(mce);
        }
    }

用法:

.OrderByField(sortcriteria, true)

编辑:

为了支持 ThenBy 方法，但是以下返回 IOrderedQueryable 的方法应该可以解决所有问题:

public static class SomeExtensionClass
{
    private static IOrderedQueryable<T> OrderingHelper<T>(IQueryable<T> source, string propertyName, bool descending, bool anotherLevel)
    {
        var param = Expression.Parameter(typeof(T), "p");
        var property = Expression.PropertyOrField(param, propertyName);
        var sort = Expression.Lambda(property, param);

        var call = Expression.Call(
            typeof(Queryable),
            (!anotherLevel ? "OrderBy" : "ThenBy") + (descending ? "Descending" : string.Empty),
            new[] { typeof(T), property.Type },
            source.Expression,
            Expression.Quote(sort));

        return (IOrderedQueryable<T>)source.Provider.CreateQuery<T>(call);
    }

    public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> source, string propertyName)
    {
        return OrderingHelper(source, propertyName, false, false);
    }

    public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> source, string propertyName, bool descending)
    {
        return OrderingHelper(source, propertyName, descending, false);
    }

    public static IOrderedQueryable<T> ThenBy<T>(this IOrderedQueryable<T> source, string propertyName)
    {
        return OrderingHelper(source, propertyName, false, true);
    }

    public static IOrderedQueryable<T> ThenBy<T>(this IOrderedQueryable<T> source, string propertyName, bool descending)
    {
        return OrderingHelper(source, propertyName, descending, true);
    }
}

关于c# - 无法使用 LINQ OrderBy 中的属性名称进行排序，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16013807/