请参考此代码
public class A : B { [Display(Name = "Initial Score Code", Order =3)] public Code { get; set; } [Display(Name = "Initial Score Code", Order =2)] public Name{ get; set; } ............ }我需要通过Display的orderAttribute通过order获取类的所有属性.我已经尝试过使用此代码来做
I need to get all properties of class through order by orderAttribute of Display. I have tried with this code to do
var prop = typeof(A) .GetProperties() .OrderBy(p => ((DisplayAttribute)p.GetCustomAttributes(typeof(DisplayAttribute), true).FirstOrDefault).Order);但是会导致错误
对象引用不设置对象实例
object reference not to set an instance of object
由于某些属性在"DisplayAttribute"中不具有"Order"属性,因此我认为这是一个问题.
I assumed this issue because of some property not having "Order" property in "DisplayAttribute" .
如何处理这种情况?我需要对所有属性进行排序,即使某些属性不具有order属性的值.
How to handle this kind of situation? I need to order all the properties even though some property not having the value of order property.
推荐答案您在 FirstOrDefault 运算符上缺少括号().还应该处理返回 default 值的情况.我建议在获取第一个或默认值之前选择 Order 值.对于所有没有 DisplayAttribute 的属性,这将返回 0 :
You are missing brackets () on FirstOrDefault operator. Also you should deal with case when default value is returned. I suggest to select Order value before getting first or default value. That will return 0 for all properties which don't have DisplayAttribute:
var prop = typeof(A) .GetProperties() .OrderBy(p => p.GetCustomAttributes(typeof(DisplayAttribute), true) .Cast<DisplayAttribute>() .Select(a => a.Order) .FirstOrDefault());如果希望不带DisplayAttribute的属性位于最后,则可以提供 Int32.MaxValue 作为要返回的默认值:
If you want properties without DisplayAttribute to be last, you can provide Int32.MaxValue as default value to be returned:
.Select(a => a.Order) .DefaultIfEmpty(Int32.MaxValue) .First()更多推荐
使用反射按顺序获取类的属性
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