如何提高PropertyChanged事件，而无需使用字符串名称 [英] How to raise PropertyChanged event without using string name

问题描述

这将是件好事，提高的PropertyChanged'事件没有明确的规定更改属性的名称能力。我愿做这样的事情：

It would be good to have ability to raise 'PropertyChanged' event without explicit specifying the name of changed property. I would like to do something like this:

    public string MyString
    {
        get { return _myString; }
        set
        {
            ChangePropertyAndNotify<string>(val=>_myString=val, value);
        }
    }

    private void ChangePropertyAndNotify<T>(Action<T> setter, T value)
    {
        setter(value);
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(setter.Method.Name));
        }
    }

在这种情况下，接收到的名字是λ-方法的名称：＆LT; set_MyString> b__0

In this case received name is a name of lambda-method: "<set_MyString>b__0".

1. 我可以肯定，即微调＆LT; SET_？和> b__0永远提供正确的属性名称
2. 是否有任何其他通知有关产权变更（由物业自己）？

感谢你。

推荐答案

更新：原来的code不是的Windows Phone友好的，因为它依赖于LambdaEx pression.Compile（ ），以获取事件源对象。下面是更新扩展方法（有参数检查删除以及）：

Update: The original code is not Windows Phone friendly, as it relies on LambdaExpression.Compile() to get the event source object. Here's the updated extension method (with parameter checks removed as well):

    public static void Raise<T>(this PropertyChangedEventHandler handler, Expression<Func<T>> propertyExpression)
    {
        if (handler != null)
        {
            var body = propertyExpression.Body as MemberExpression;
            var expression = body.Expression as ConstantExpression;
            handler(expression.Value, new PropertyChangedEventArgs(body.Member.Name));
        }
    }

用法保持如下。

The usage stays as below.

您可以使用反射在lambda函数调用的属性getter获得属性名。请注意，你实际上并不需要调用该拉姆达，你只需要它的思考：

You can get the property name using reflection on a lambda function that calls the property getter. note that you don't actually have to invoke that lambda, you just need it for the reflection:

public static class INotifyPropertyChangedHelper
{
    public static void Raise<T>(this PropertyChangedEventHandler handler, Expression<Func<T>> propertyExpression)
    {
        if (handler != null)
        {
            var body = propertyExpression.Body as MemberExpression;
            if (body == null)
                throw new ArgumentException("'propertyExpression' should be a member expression");

            var expression = body.Expression as ConstantExpression;
            if (expression == null)
                throw new ArgumentException("'propertyExpression' body should be a constant expression");

            object target = Expression.Lambda(expression).Compile().DynamicInvoke();

            var e = new PropertyChangedEventArgs(body.Member.Name);
            handler(target, e);
        }
    }

    public static void Raise<T>(this PropertyChangedEventHandler handler, params Expression<Func<T>>[] propertyExpressions)
    {
        foreach (var propertyExpression in propertyExpressions)
        {
            handler.Raise<T>(propertyExpression);
        }
    }
}

下面是如何使用该助手在你的类引发事件的一个或多个属性：

Here's how you can use that helper in your class to raise the event for one or multiple properties:

PropertyChanged.Raise(() => this.Now);
PropertyChanged.Raise(() => this.Age, () => this.Weight);

请注意，这个助手也无操作的情况下，的PropertyChanged 是空。

Note that this helper also is a no-op in case the PropertyChanged is null.

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