如何进行事件以更改定制属性(定制控件) [英] How to make events for changing custom made properties (custom control)
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问题描述
我具有从TextBox类继承的自定义控件,并且我添加了一些属性,例如,我具有placeHolderText属性,并且我想拥有一些在更改文本时会发生的事件?
像这些事件一样
而且在设计器视图$ b中有我的财产$ b
如何实现?
I have custom control inheriting from TextBox class , and i have added some properties , for example i have property placeHolderText and i want to have some event which will occur when i change that text?
Like these events
And there is my property in designer view
How to achieve that?
推荐答案
要在C#中创建事件,您可以遵循标准.NET事件模式。
To create an event in C# you can follow Standard .NET event patterns.
为某物
属性创建 Changed
事件自定义控件,您可以按照以下步骤操作:
To create a Changed
event for a Something
property of a custom control, you can follow these steps:
- 声明一个事件
SomethingChanged
。它可以是任何委托,作为一般委托,您可以依靠EventHandler
委托或EventHandler< T>
您想要一个特定的事件参数,而不是使用EventArgs
。 - 创建受保护的虚拟
OnSomethingChanged
方法,该方法接受事件args并负责引发事件。因此,如果使用此方法,则应在正文中引发事件。 - 在属性设置器中,检查该值是否与当前值不同,进行分配,然后调用
OnSomethingChanged
引发事件。
- Declare an event
SomethingChanged
. It can be any delegate, as a general delegate you can rely onEventHandler
delegate orEventHandler<T>
, in case which you want to have a specific event argument rather than usingEventArgs
. - Create a protected virtual
OnSomethingChanged
method which accepts the event args and is responsible to raising the event. So you should raise the event in body if this method. - In the property setter, check if the value is different from current value, assign it and call
OnSomethingChanged
to raise the event.
示例
public EventHandler PlaceHolderChanged;
string placeholder;
public string PlaceHolder
{
get { return placeholder; }
set
{
if (placeholder != value)
{
placeholder = value;
OnPlaceHolderChanged(EventArgs.Empty);
}
}
}
protected virtual void OnPlaceHolderChanged(EventArgs e)
{
PlaceHolderChanged?.Invoke(this, e);
}
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