[ACCEPTED]-C#:Creating Multicast delegate with boolean return type-delegates
public delegate bool Foo(DateTime timestamp);
This is how to declare a delegate with the 9 signature you describe. All delegates are 8 potentially multicast, they simply require 7 initialization. Such as:
public bool IsGreaterThanNow(DateTime timestamp)
{
return DateTime.Now < timestamp;
}
public bool IsLessThanNow(DateTime timestamp)
{
return DateTime.Now > timestamp;
}
Foo f1 = IsGreaterThanNow;
Foo f2 = IsLessThanNow;
Foo fAll = f1 + f2;
Calling fAll, in this 6 case would call both IsGreaterThanNow() and IsLessThanNow().
What this doesn't 5 do is give you access to each return value. All 4 you get is the last value returned. If 3 you want to retrieve each and every value, you'll 2 have to handle the multicasting manually 1 like so:
List<bool> returnValues = new List<bool>();
foreach(Foo f in fAll.GetInvocationList())
{
returnValues.Add(f(timestamp));
}
class Test
{
public delegate bool Sample(DateTime dt);
static void Main()
{
Sample j = A;
j += B;
j(DateTime.Now);
}
static bool A(DateTime d)
{
Console.WriteLine(d);
return true;
}
static bool B(DateTime d)
{
Console.WriteLine(d);
return true;
}
}
0
Any delegate can be a multicast delegate
delegate bool myDel(DateTime s);
myDel s = someFunc;
s += someOtherFunc;
A 9 useful property of delegate objects is 8 that they can be assigned to one delegate 7 instance to be multicast using the + operator. A 6 composed delegate calls the two delegates 5 it was composed from. Only delegates of the 4 same type can be composed.
EDIT: A delagate has 3 a method GetInvocationList which returns a list with the 2 attached methods.
Here is a reference about 1 Delegate invocation
foreach(myDel d in s.GetInvocationList())
{
d();
}
I was stumbling upon the same problem. I 5 searched and found this in msdn.
http://msdn.microsoft.com/en-us/library/2e08f6yc(v=VS.100).aspx
There are 4 two methods on delegates
- BeginInvoke
- EndInvoke
The link describes 3 these in detail, with code samples.
We can 2 hook into these methods to handle the return 1 values of the delegates.
In your case , Instead of creating a delegate 2 yourself ,
it is better to use pre-defined 1 delegates in C# such as Func and Predicate :
public delegate TResult Func<in T1, in T2, out TResult>(T1 arg1, T2 arg2);
and
public delegate bool Predicate<in T>(T obj);
More Related questions
We use cookies to improve the performance of the site. By staying on our site, you agree to the terms of use of cookies.