What are Anonymous Types in C#?

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Hi
Sir, I can't understand this code. Please help me.

C#

using System;
using System.Collections;
using System.Collections.Generic;

class Test
{
    //Prints the contents of any generic Stack by using generic type inference
    public static void PrintStackContents<T>(Stack<T> s)
    {
        while(s.Count != 0)
        {
            Console.WriteLine(s.Pop());
        }
    }

    public static void Main(String[] args)
    {
        Stack<int> s2 = new Stack<int>();
        s2.Push(4);
        s2.Push(5);
        s2.Push(6);

        PrintStackContents(s2);

        Stack<string> s1 = new Stack<string>();
        s1.Push("One");
        s1.Push("Two");
        s1.Push("Three");

        PrintStackContents(s1);
    }
}

And also, what is the use of Anonymous Types in C#?

Posted 4-Mar-11 20:34pm

sairam.bhat

Updated 5-Mar-11 8:08am

Toli Cuturicu

v2

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-03-05T18:13:00

Just my addition to point out how important anonymous methods are: they are a big step into functioning programming.

First, please see my Tips/Trick article on hiding methods in other methods: Hide Ad-hoc Methods Inside the Calling Method’s Body[^].

Then, good style of programming event handler is using anonymous methods: how to call keydown event on particular button click[^] (also, pay attention to lambda notation as a convenient alternative).

The anonymous methods are important in using of invocation mechanism for UI threads, both WPF and System.Windows.Forms, Control.Invoke() vs. Control.BeginInvoke()[^], this mechanism can be used in more general case for a custom thread, see my Tips/Trips article on the topic: Simple Blocking Queue for Thread Communication and Inter-thread Invocation[^].

Also, just to understand that not everything is easy, get an idea of closures (http://en.wikipedia.org/wiki/Closure_(computer_science)[^]), which only can be implemented using anonymous methods, see another Answer: Looping for creating new thread give some problem[^].

—SA

OriginalGriff · Accepted Answer · 2011-03-04T21:14:00

The PrintStackContents method:

C#

public static void PrintStackContents<T>(Stack<T> s)
    {
    while(s.Count != 0)
        {
        Console.WriteLine(s.Pop());
        }
    }

Is a Generic routine: you have defined it to work for any class by adding the <T> after the method name. Within the method, you can now use "T" and the compiler with substitute the class type when you call the method.
Effectively, what you could have done is write a separate method for each type:

C#

public static void PrintStackContentsInt(Stack<int> s)
    {
    while(s.Count != 0)
        {
        Console.WriteLine(s.Pop());
        }
    }
public static void PrintStackContentsString(Stack<string> s)
    {
    while(s.Count != 0)
        {
        Console.WriteLine(s.Pop());
        }
    }

And so on: But by using the Generic syntax, you only have to code and maintain a single method, which will work the same for them all.

Anonymous types are more complex, and are probably best left until latter when you start to learn about Linq, but a brief description:
An anonymous type is a class with no name: you do not define it directly with a class statement, instead it's structure is inferred from the data from which it is created. They are frequently used to return the results of a Linq query.

Piccadilly Yum Yum · Accepted Answer · 2011-03-04T21:19:00

Anonymous Types Defined
The C# 3.0 specifications describe anonymous types as tuple types automatically inferred and created from object initializers. Before you can fully understand the meaning of this definition, you need to understand the term "object initializer," which is the basis of the anonymous types feature.
An object initializer specifies values from one or more fields or properties of an object. That means you specify a set of properties for an object through a series of assignments, such as {a = 10, b = 20}, and an object is assigned these properties. In other words, an anonymous type is one that previously did not exist and was not defined explicitly in code.
Note: The compiler creates the anonymous type at compile time and not run time.

Just removed the block code.

What are Anonymous Types in C#?

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