c# - 通过反射按自定义属性对实体进行 Linq 排序

Question

得到 Customer类有 Country具有字符串属性的属性 Name . 还有 Customer工具 IComparable<Country>像这样:

public int CompareTo(Country other)
{
    return string.Compare(this.Name, other.Name);
}

现在:

var custList = new List<Customer>{...};

custList.OrderBy(cust => cust.Country).ToList(); //Sorts as charm.

如果尝试通过反射排序:

var itemProp = typeof(Customer).GetProperty("Country");

custList = c.Customers.ToList()
    .OrderBy(cust => itemProp.GetValue(cust, null)).ToList(); // Fails

抛出异常'至少一个对象必须实现 IComparable'

请解释失败的原因以及如何通过反射正确地按自定义属性对客户进行排序。谢谢。

Answer 1

由于 GetValue 返回 Object，您需要实现 IComparable 的非泛型版本。

void Main()
{
    var custList = new List<Customer>()
    { 
        new Customer(){ Country = new Country(){ Name = "Sweden" } },
        new Customer(){ Country = new Country(){ Name = "Denmark" } },
    };

    var itemProp = typeof(Customer).GetProperty("Country");

    custList = custList.OrderBy(cust => itemProp.GetValue(cust, null)).ToList();

    custList.Dump();
}

public class Country : IComparable<Country>, IComparable
{
    public string Name {get;set;}

    public int CompareTo(Country other)
    {
        return string.Compare(this.Name, other.Name);
    }

    public int CompareTo(object other)
    {
        var o = other as Country;
        if(o == null)
            return 0; //Or how you want to handle it
        return CompareTo(o);
    }
}

public class Customer
{
    public Country Country{get;set;}
}