使用属性名称构建OrderBy表达式 [英] Building an OrderBy expression using the name of a property

问题描述

我试图通过MVC3中的WebGrid控件支持排序，该控件通过sort参数将模型上属性的名称传递给我的操作.

I'm trying to support sorting via the WebGrid control in MVC3, which passes the name of a property on my model into my actions via a sort parameter.

public class Agent {
    public int Id { get; set; }
    public string Name { get; set; }
}

[HttpGet]
public ActionResult Index(string sort = "Id", string sortdir = "ASC") {

    // Define the parameter that we are going to use in the OrderBy clause.
    var param = Expression.Parameter(typeof(Agent), "agent");

    // Now we'll make our lambda function that returns the
    // property's value by it's name.
    var sortExpression = Expression.Lambda<Func<Agent, object>>(Expression.Property(param, sort), param);

    var agents = entities.OrderBy(sortExpression).ToList();

    var model = new PagedResult<Agent> {

        CurrentPage = 1,
        PageCount = 1,
        PageSize = DefaultPageSize,
        Results = agents,
        RowCount = agents.Count

    };

    return View(model);
}

当我尝试通过类型为string的Name属性对模型进行排序时，此代码有效.但是，如果我尝试按Id进行排序，则会收到错误Expression of type 'System.Int32' cannot be used for return type 'System.Object'.

This code works when I try to sort my model by the Name property, which is of type string. However, if I try to sort by Id I receive the error Expression of type 'System.Int32' cannot be used for return type 'System.Object'.

推荐答案

您可以使用Expression.Convert进行装箱.

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