Delegates and Callbacks
c#, callback
Solution
Your example is a good start, but it is incorrect. You don't make a new delegate in the method, it's used in the declaration of an event in the class. See this modified example of your code:
namespace Test
{
//In this case, this delegate declaration is like specifying a specific kind of function that must be used with events.
public delegate string CallbackDemo(string str);
class Program
{
public static event CallbackDemo OnFoobared;
static void Main(string[] args)
{
//this means that StrAnother is "subscribing" to the event, in other words it gets called when the event is fired
OnFoobared += StrAnother;
string substr = Strfunc();
Console.WriteLine(substr);
Console.ReadKey(true);
//this is the other use of delegates, in this case they are being used as an "anonymous function".
//This one takes no parameters and returns void, and it's equivalent to the function declaration
//'void myMethod() { Console.WriteLine("another use of a delegate"); }'
Action myCode = delegate
{
Console.WriteLine("another use of a delegate");
};
myCode();
Console.ReadKey(true);
//the previous 4 lines are equivalent to the following however this is generally what you should use if you can
//its called a lambda expression but it's basically a way to toss arbitrary code around
//read more at http://www.developer.com/net/csharp/article.php/3598381/The-New-Lambda-Expressions-Feature-in-C-30.htm or
//http://stackoverflow.com/questions/167343/c-lambda-expression-why-should-i-use-this
Action myCode2 = () => Console.WriteLine("a lambda expression");
myCode2();
Console.ReadKey(true);
}
static string Strfunc()
{
return OnFoobared("a use of a delegate (with an event)");
}
static string StrAnother(string str)
{
return str.Substring(1, 3).ToString();
}
}
}
I've only scratched the surface here; search stack overflow for "delegate c#" and "lambda expression c#" for lots more!
Problem
Does the term callback in the context of delegates mean ,"a delegate delegating it works to another delegate inorder to finish some task" ? Example :(Based on my understanding,I have implemented a callback,correct me if it is wrong) ``` namespace Test { public delegate string CallbackDemo(string str); class Program { static void Main(string[] args) { CallbackDemo handler = new CallbackDemo(StrAnother); string substr = Strfunc(handler); Console.WriteLine(substr); Console.ReadKey(true); } static string Strfunc(CallbackDemo callback) { return callback("Hello World"); } static string StrAnother(string str) { return str.Substring(1, 3).ToString(); } } } ``` Please provide examples as necessary.