如何在 WPF 4.5 中为按钮单击事件制作 MarkupExtenstion?

问题描述

我想创建 MarkupExtension 以提供对按钮单击事件的支持.我有一篇关于 PreviewKeyDown 的文章 此处.我试图为 Click 修改它但无法这样做，因为它引发了异常

I want to create the MarkupExtension to provide support for Button click event. I have got an article for PreviewKeyDown here. I tried to modify it for Click but unable to do so as it throws an exception

请建议如何实施.

推荐答案

看起来它试图将 MethodInfo 转换为 EventInfo，返回的目标属性可能是一个 MethodInfo 或 EventInfo 您必须在创建委托之前检查这一点

Looks like its trying to cast MethodInfo as EventInfo, the returned target property could be a MethodInfo or EventInfo you will have to check this before createing the delegate

试试这个

    public class Call : MarkupExtension
    {
        public string ActionName { get; set; }
        public Call(string actionName) { ActionName = actionName; }

        public override object ProvideValue(IServiceProvider serviceProvider)
        {
            IProvideValueTarget targetProvider = serviceProvider
                .GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;
            if (targetProvider == null)
                throw new InvalidOperationException(@"The CallAction extension
                can't retrieved the IProvideValueTarget service.");

            var target = targetProvider.TargetObject as FrameworkElement;
            if (target == null)
                throw new InvalidOperationException(@"The CallAction extension
                    can only be used on a FrameworkElement.");

            if (targetProvider.TargetProperty is MethodInfo)
            {
                var targetEventAddMethod = targetProvider.TargetProperty as MethodInfo;
                if (targetEventAddMethod != null)
                {
                    ParameterInfo[] pars = targetEventAddMethod.GetParameters();
                    Type delegateType = pars[1].ParameterType;
                    MethodInfo methodInfo = this.GetType().GetMethod("MyProxyHandler", BindingFlags.NonPublic | BindingFlags.Instance);
                    return Delegate.CreateDelegate(delegateType, this, methodInfo); ;
                }

            }
            else if (targetProvider.TargetProperty is EventInfo)
            {
                var targetEventInfo = targetProvider.TargetProperty as EventInfo;
                if (targetEventInfo != null)
                {
                    Type delegateType = targetEventInfo.EventHandlerType;
                    MethodInfo methodInfo = this.GetType().GetMethod("MyProxyHandler", BindingFlags.NonPublic | BindingFlags.Instance);
                    return Delegate.CreateDelegate(delegateType, this, methodInfo);
                }
            }
            return null;
        }

        void MyProxyHandler(object sender, EventArgs e)
        {
            FrameworkElement target = sender as FrameworkElement;
            if (target == null) return;
            var dataContext = target.DataContext;
            if (dataContext == null) return;

            //get the method on the datacontext from its name
            MethodInfo methodInfo = dataContext.GetType()
                .GetMethod(ActionName, BindingFlags.Public | BindingFlags.Instance);
            methodInfo.Invoke(dataContext, null);
        }
    }

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