C# 另一个类中的DownloadStringCompletedEventHandler回调
我有两节课,下面是在我继续提问之前发生的事情的分类 myClass1:C# 另一个类中的DownloadStringCompletedEventHandler回调,c#,callback,C#,Callback,我有两节课,下面是在我继续提问之前发生的事情的分类 myClass1: myClass1(){ myClass2 c2 = new myClass2(); c2.service(); } public void myFunction1(){ Console.Write("Function returned!"); } public void service(){ callWebService(myFunction1); // The paramete
myClass1(){
myClass2 c2 = new myClass2();
c2.service();
}
public void myFunction1(){
Console.Write("Function returned!");
}
public void service(){
callWebService(myFunction1); // The parameter you pass here is the function that control
// will pass back to once the called function is done.
}
public void callWebService(DownloadStringCompletedEventHandler callback){
//Calls web service and does some other operations
}
myClass2:
myClass1(){
myClass2 c2 = new myClass2();
c2.service();
}
public void myFunction1(){
Console.Write("Function returned!");
}
public void service(){
callWebService(myFunction1); // The parameter you pass here is the function that control
// will pass back to once the called function is done.
}
public void callWebService(DownloadStringCompletedEventHandler callback){
//Calls web service and does some other operations
}
最后是问题。正如您在上面看到的,我有两个类,class1调用class2中的函数。该函数调用类2中另一个调用Web服务的函数。一旦web服务完成,控制流就会传回函数调用中传递的任何函数
但这意味着您只能使用一个类,因为回调函数应该在同一个类中。所以问题是,我如何在另一个类中传递一个函数作为回调函数
希望所有这些都是有意义的,请不要犹豫问任何事情来澄清一点。谢谢 您可以修改
服务
类并将MyClass1的
方法传递给它。例如,在下面的代码中,函数ServiceCallComplete
作为参数传递给服务
类构造函数
函数可以另存为或委托类型(取决于回调函数定义)。服务作业完成后,调用委托(\u callback()
)将在MyClass1
上调用回调函数
public class MyClass1
{
//The callback Function
public void ServiceCallComplete()
{
Console.WriteLine("Function returned.");
}
}
public class Service
{
//delegate to store the callback function.
private readonly Action _callBack;
public Service(Action callBack)
{
//store the callback function
_callBack = callBack;
}
public void Method()
{
//long running operation
.
.
//Invoke the callback
_callBack();
}
}
MyClass1 obj = new MyClass1();
Service svc = new Service(obj.ServiceCallComplete);
svc.Method();
不要传递委托,而是使用事件:
class MyClass1
{
public MyClass1()
{
var c2 = new MyClass2();
c2.ActionwebServiceCalled += MyCallBack; //register for the event
c2.CallWebService();
}
public void MyCallBack(object sender, DownloadStringCompletedEventArgs e)
{
Console.Write("Function returned!");
}
}
class MyClass2
{
public event DownloadStringCompletedEventHandler ActionwebServiceCalled;
public void CallWebService()
{
DownloadStringCompletedEventArgs e = null;
//Calls web service and does some other operations...
var handler = ActionwebServiceCalled;
if (handler != null)
handler(this, e);
}
}
话虽如此,您可能希望在web服务调用中引入异步,在这种情况下,只要您有.NET4(),就可以这样做。对于.NET3.5及更低版本,您需要遵循以下步骤