使用Lambda识别属性名称 [英] Using lambda to identify property name
问题描述
我对以下代码有疑问:
public class MyClass : INotifyPropertyChanged
{
private bool _myProp;
public bool MyProp
{
get { return _myProp; }
set
{
_myProp = value;
RaisePropertyChanged(() => MyProp);
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected void RaisePropertyChanged(string name)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(name));
}
}
这可能不是识别属性名称的最佳方法,但是我以前使用过它,即使在同一项目中也是如此.但是,以上代码无法编译.有几种解决方法.其中一些可能是比上面更好的解决方案,但是,我仍然想找出为什么这不起作用.
This may not be the best way to identify a property name, but I have used it before, even in the same project; however, the above code won't compile. There's several workarounds for this; some of which may be better solutions that what is above, however, I'd still like to find out why this doesn't work.
我得到的具体编译错误是:
The specific compile error I get is:
error CS1660: Cannot convert lambda expression to type 'string' because it is not a delegate type
推荐答案
您需要一种方法,该方法接受 Expression< Func< T>>
,将属性名称提取为字符串,然后引发 PropertyChanged
事件.它不会自动完成.我通常将其作为扩展方法,以免一遍又一遍地实现相同的代码或将其保存在基类中.
You need a method that accepts Expression<Func<T>>
, extracts the property name as a string, and then raises the PropertyChanged
event with it. It won't be done automatically. I usually make it an extension method, to save implementing the same code over and over or having it in a base class:
public static class RaisePropertyChangedExtensions
{
public static void RaisePropertyChanged<T>(
this IRaisePropertyChanged raisePropertyChangedImpl,
Expression<Func<T>> expr)
{
var memberExprBody = expr.Body as MemberExpression;
string property = memberExprBody.Member.Name;
raisePropertyChangedImpl.RaisePropertyChanged(property);
}
}
您的视图模型只需要实现 IRaisePropertyChanged
接口:
Your view-models just need to implement the IRaisePropertyChanged
interface:
public interface IRaisePropertyChanged : INotifyPropertyChanged
{
void RaisePropertyChanged(string property);
}
..并且用法与您的问题完全相同:
..and the usage is exactly the same as in your question:
this.RaisePropertyChanged(() => MyProp);
当然,您始终可以将其作为视图模型的一种方法-只需删除通用参数并将视图模型类型传递给函数即可.
Of course, you can always make this a method on your view-model - just remove the generic parameter and pass your view-model type to the function.
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