在LINQ的秩序将重点by子句动态 [英] Set key inside order by clause in linq dynamically

问题描述

我需要设置使用LINQ的排序依据条款，其中关键是一个对象的属性的关键。我只有用我的属性名称。我怎么能动态设置属性。

I need to set the key in the OrderBy clause using linq , where the key is a property of an object. I only have the property name with me. How can i set the property dynamically.

class Obj 
{
    string Level
    {
       get;
       set;
    }
}

List<Obj> objList;

objList.OrderByDescending(x => x.Level); => "here i only have property name."

希望任何一个可以帮助

Hope any one can help

谢谢
苏尼尔

推荐答案

您可以通过的扩展方法 和的创建表达式树 动态像

You can do this by Extension Methods and Creating Expression Trees dynamically like

public static IOrderedQueryable<T> OrderByDescending<T>(this IQueryable<T> enumerable, string sortColumn)
{
    var param = Expression.Parameter(typeof(T), "x");
    var mySortExpression = Expression.Lambda<Func<T, object>>(Expression.Property(param, sortColumn), param);
    return enumerable.OrderByDescending(mySortExpression);;
 }

和为排序依据

public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> enumerable, string sortColumn)
{
    var param = Expression.Parameter(typeof(T), "x");
    var mySortExpression = Expression.Lambda<Func<T, object>>(Expression.Property(param, sortColumn), param);
    return enumerable.OrderBy(mySortExpression);;
 }

和您可以在一个结合这两种像

and you can combine these two in one like

public static IOrderedQueryable<T> OrderBy<T>(this IQueryable<T> enumerable, string sortColumn, string direction)
{
     var param = Expression.Parameter(typeof(T), "x");
     var mySortExpression = Expression.Lambda<Func<T, object>>(Expression.Property(param, sortColumn), param);

      IOrderedQueryable<T> iQuery;
      switch(direction)
      {
          case "desc": 
            iQuery = enumerable.OrderByDescending(mySortExpression);
            break;
          case "asc":
          default :
            iQuery = enumerable.OrderBy(mySortExpression);
            break;
      }
      return iQuery;
 }

然后就可以调用它像 objList.OrderBy（ 级别，ASC） //对于升序
objList.OrderBy（级别，降序） //对于降序

Then you can call it like objList.OrderBy("Level","asc") //For Ascending objList.OrderBy("Level","desc") //For Descending

希望这将有助于

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