Question

The following code works fine (it builds a generic OrderBy):

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);

But, I woud like to change this line, in this way:

var _OrderByLambda = Expression.Lambda<Func<Item, object>>
    (_OrderByBody, _OrderByParameter);

Such a change would make the data type of the ordered column generic. However, such a change results in the following exception:

Expression of type ‘System.Int32’ cannot be used for return type ‘System.Object’

Any ideas?

EDIT, thank you for your answers, this works fine:

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);

Answer 1

You need to specify that the return type of the body is exactly System.Object. You can do this by inserting a conversion (something C# does implicitly):

_OrderByBody = Expression.Convert(_OrderByBody, typeof(object));