没有静态的单个对象实例 [英] Single Object Instance without static

问题描述

我知道我很懒，但只是为了检查是否有更好的想法。

我在用户控件中有一个事件

Hi I know i am lazy but just to check if there is any better ideas around.
I had an event in a usercontrol

public event EventHandler EH_OpenDefaultClick;

单击单选按钮时的表单将订阅此事件。但是这个表单不会被销毁，只要单击单选按钮，我就会订阅该事件

A form when a radio button is click will subscribe to this event. However this form will not be destroyed and whenever the radio button is click, i will subscribe to the event

ucStdButton_Recipe.EH_OpenDefaultClick += ucStdButton_Recipe_EH_OpenDefaultClick;

只有上面的唯一一行，每次订阅，因此触发多次。我可以添加代码来比较它是否为null。但最终代码对所有这些都不整齐== null

with the only line above, every time it will be subscribe, hence triggering multiple time. I can add in the code to compare if it is null. But eventually codes get untidy with all these == null

if (ucStdButton_Recipe.EH_OpenDefaultClick == null)
    ucStdButton_Recipe.EH_OpenDefaultClick += ucStdButton_Recipe_EH_OpenDefaultClick;

我无法将事件声明为静态，因为事件是在运行时订阅的。是否有任何声明类型允许我在没有比较语句的情况下更容易订阅

I cannot declare the event as static as the event is subscribe during runtime. Is there any declaration type allowing me to subscribe more easily without the comparison statement

推荐答案

您可以检查特定的处理程序订阅：

You can check for a specific handler subscription:

public bool IsHandlerSubbed(Delegate handler)
{   
	if ( this.EventHandler != null )
	{
		foreach ( Delegate h in this.EventHandler.GetInvocationList() )
		{
			if ( h == handler)
			{
				return true;
			}
		}
	}
	return false;
}

您可以在添加之前通过取消订阅来阻止它：

You can prevent it by unsubscribing before adding it:

ucStdButton_Recipe.EH_OpenDefaultClick -= ucStdButton_Recipe_EH_OpenDefaultClick;
ucStdButton_Recipe.EH_OpenDefaultClick += ucStdButton_Recipe_EH_OpenDefaultClick;

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