This is an extension of my earlier blog post. I myself, find delegates as one of the most powerful types to use in C#. It helps in writing very flexible and scalable programs.
I already discussed in my last blog that in the traditional way, we need to write more code. There I also discussed, one predefined delegate Action delegate that is provided by the framework. There are four flavors of Action delegate provided.
One more type of predefined delegate that is provided by .NET is the counterpart Action delegate. As we saw, it always returns void
. But Func returns a value instead of void
as Action does.
There are also 5 flavours of the Func
delegate that are provided. These are:
Public delegate TResult Func<TResult>()
-
Public delegate TResult Func<TResult>()
-
Public delegate TResult Func<T, TResult>(T t)
-
Public delegate TResult Func<T1, T2, TResult>(T1 t1, T2 t2)
-
Public delegate TResult Func<T1, T2, T3, TResult>(T1 t1, T2 t2, T3 t3)
-
Public delegate TResult Func<T1, T2, T3, T4, TResult>
(T1 t1, T2 t2, T3 t3,T4 t4)
If we see the declaration, TResult
is put last, this is just a convention. One can put it wherever s/he wants.
First let's see first one, with no parameter and returning a value:
public class Program
{
static void Main(string[] args)
{
Func<string> myFunc = SayHello;
string returnedString = myFunc();
Console.WriteLine(returnedString);
Console.ReadKey();
}
private static string SayHello()
{
return "Hello Dude!!";
}
}
Now let's move to code to another overload of Func
Delegate. It takes two input parameters and returns a value.
public class Program
{
static void Main(string[] args)
{
Func<double, double, double> myFunc1 = Add;
double sum = myFunc1(3.5, 4.5);
Console.WriteLine(sum);
Console.ReadKey();
}
private static double Add(double first, double second)
{
return first + second;
}
}
It is also the same as Action delegate, i.e., it can also be used with Anonymous functions and Lambda functions. Let's have a quick look at both:
Anonymous Function
public class Program
{
static void Main(string[] args)
{
Func<double, double, double, double> myFunc1 = delegate(double d1, double d2, double d3)
{
return d1 + d2 + d3;
};
double sum = myFunc1(3.5, 4.5, 5.5);
Console.WriteLine(sum);
Console.ReadKey();
}
}
Lambda Function
public class Employee
{
public int Id { get; set; }
public string Name { get; set; }
}
public class Program
{
static void Main(string[] args)
{
Func<Employee,string> checkEmployee = s=>{
if (s.Id > 11)
return s.Name;
else
return "Employee is not with the given Criteria.";
};
Console.WriteLine(checkEmployee(new Employee() {Id=12, Name="Brij"}));
Console.WriteLine(checkEmployee(new Employee() {Id=10, Name="Abhijit"}));
Console.ReadKey();
}
}
Hope you all enjoyed the delegates.
We use delegates a lot. But most of us use the traditional way in programs. When I learnt first these Action
and Func
delegates a few weeks ago, I found them very useful. It helps us in writing better and well organised code, which is also less error prone. I talked to a lot of developers, they didn’t have any idea about these predefined delegates. So I thought of sharing with all of you.
Please share your valuable feedback.
Cheers,
Brij
Brij is a 3-times Microsoft MVP in ASP.NET/IIS Category and a passionate .NET developer. More than 6 years of experience in IT field, currently serving a MNC as a Tech Lead/Architect.
He is a very passionate .NET developer and have expertise over Web technologies like ASP.NET 2.0/3.5/4.0, jQuery, JSON, Javascript, IIS and related technologies. He is also a Exchange Server (EWS) Specialist. He has great experience in design patterns and N-Tier Architecture.
He is also certified as Microsoft Certified Technologies Specialist-ASP.NET and Microsoft Certified Technologies Specialist-WCF in .NET 4.0. He has also received several awards at various forums and his various articles got listed as "Article of the day" at ASP.NET Microsoft Official Website www.asp.net.
He has done MCA from NIT Durgapur and completed his graduation from Lucknow University.
Learning new technologies and sharing knowledge excites him most. Blogging, solving problems at various forums, helping people, keeps him busy entire day.
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Area of Expertise :
C#, ASP.NET 2.0,3.5,4.0, AJAX, JQuery, JSON, XML, XSLT, ADO.Net, WCF, Active Directory, Exchange Server 2007 (EWS), Java script, Web Services ,Win services, DotnetNuke, WSS 3.0,Sharepoint Designer, SQL Server 2000/2005/2008