[英]Trigger an event from within another class
在.NET中,我有一个名为Caption的类。 我还有另一门课,叫做“量规”。 在Gauge类中,我有一个定义为Caption的属性。
我试图弄清楚如何执行以下操作:当Caption类中的某个属性发生更改时,如何获取它以执行Gauge类中的子例程? 我在想我必须声明一个事件并使用AddHandlers来触发它,但是我无法考虑如何完成此操作。
public class Caption
{
private int myInt;
public event EventHandler MyIntChanged;
private void OnMyIntChanged()
{
var handler = this.MyIntChanged;
if (handler != null)
{
handler(this, EventArgs.Empty);
}
}
public int MyInt
{
get
{
return this.myInt;
}
set
{
if (this.myInt != value)
{
this.myInt = value;
this.OnMyIntChanged();
}
}
}
}
所以现在,在您的guage类中:
public class Guage
{
private Caption caption;
public Caption Caption
{
get
{
return this.caption;
}
set
{
if (this.caption!= value)
{
this.caption= value;
this.caption.MyIntChanged += new EventHandler(caption_MyIntChanged);
}
}
}
private void caption_MyIntChanged(object sender, EventArgs e)
{
//do what you gotta do
}
}
您将要考虑实现INotifyPropertyChanged接口,该接口正是为此目的而设计的-当类实例的属性更改时引发一个事件。
这个MSDN页面给出了一个用法的很好的例子。
// This class implements a simple customer type
// that implements the IPropertyChange interface.
public class DemoCustomer : INotifyPropertyChanged
{
// These fields hold the values for the public properties.
private Guid idValue = Guid.NewGuid();
private string customerName = String.Empty;
private string companyNameValue = String.Empty;
private string phoneNumberValue = String.Empty;
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
// The constructor is private to enforce the factory pattern.
private DemoCustomer()
{
customerName = "no data";
companyNameValue = "no data";
phoneNumberValue = "no data";
}
// This is the public factory method.
public static DemoCustomer CreateNewCustomer()
{
return new DemoCustomer();
}
// This property represents an ID, suitable
// for use as a primary key in a database.
public Guid ID
{
get
{
return this.idValue;
}
}
public string CompanyName
{
get {return this.companyNameValue;}
set
{
if (value != this.companyNameValue)
{
this.companyNameValue = value;
NotifyPropertyChanged("CompanyName");
}
}
}
public string PhoneNumber
{
get { return this.phoneNumberValue; }
set
{
if (value != this.phoneNumberValue)
{
this.phoneNumberValue = value;
NotifyPropertyChanged("PhoneNumber");
}
}
}
}
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