以下代码可以正常工作(构建通用的OrderBy):
这样的更改将使有序列的数据类型成为通用型。但这样的更改会导致以下异常:
“无法将类型为'System.Int32'的表达式用于返回类型'System.Object'”
有什么想法吗?
编辑,感谢您的回答,这很好用:
public class Item
{
public int Value { get; set; }
public string Name { get; set; }
}
var _List = new List<Item>
{
new Item{ Name = "Smith", Value = 3},
new Item{ Name = "Smith", Value = 2},
new Item{ Name = "Wesson", Value = 1},
new Item{ Name = "Wesson", Value = 4},
}.AsQueryable<Item>();
var _Type = typeof(Item);
// OrderBy
var _OrderByProperty = _Type.GetProperty("Value");
var _OrderByParameter = Expression.Parameter(typeof(Item), "x");
// OrderBy(x => x.Value)
var _OrderByBody = Expression.Property(_OrderByParameter, _OrderByProperty.Name);
var _OrderByLambda = Expression.Lambda<Func<Item, Int32>>
(_OrderByBody, _OrderByParameter);
// apply the OrderBy
_List = _List.OrderBy(_OrderByLambda);
但是,我想以这种方式更改此行:
var _OrderByLambda = Expression.Lambda<Func<Item, object>>
(_OrderByBody, _OrderByParameter);
这样的更改将使有序列的数据类型成为通用型。但这样的更改会导致以下异常:
“无法将类型为'System.Int32'的表达式用于返回类型'System.Object'”
有什么想法吗?
编辑,感谢您的回答,这很好用:
var _OrderByProperty = _Type.GetProperty("Value");
var _OrderByParameter = Expression.Parameter(typeof(Item), "x");
// OrderBy(x => x.Value)
var _OrderByBody = Expression.Property(_OrderByParameter, _OrderByProperty.Name);
var _OrderByConverted = Expression.Convert(_OrderByBody, typeof(object));
var _OrderByLambda = Expression.Lambda<Func<Item, object>>
(_OrderByConverted, _OrderByParameter);
// apply the OrderBy
_List = _List.OrderBy(_OrderByLambda);