Anonymous type
In this chapter you will learn:
var
Declare a variable using the special type var,
and then define the type's content using the new keyword.
Anonymous types encapsulate a set of properties into a single object.
The types of the properties in an anonymous type are inferred by the compiler.
You use var to declare variable.
C# infers the type of the variable.
using System;// j a v a2s.c om
class Program
{
static void Main(string[] args)
{
var i = 5;
Console.WriteLine(i);
Console.WriteLine(i.GetType());
var str = "java2s.com";
Console.WriteLine(str);
Console.WriteLine(str.GetType());
var f = 0.0F;
Console.WriteLine(f);
Console.WriteLine(f.GetType());
}
}
The output:
var type variable is static typed. You cannot change the type for a var-type variable.
using System;/* j av a 2 s .c o m*/
class Program
{
static void Main(string[] args)
{
var i = 5;
i = "java2s.com";
}
}
The code above has the following error message:
The following fragment creates an anonymous type with two properties a string and an int.
var my = new {
Name = "Your Name",
Age = 37;
};
The values of the properties can be
accessed by calling my.Name and my.Age.
Limitations on anonymous types
Anonymous types have some limitations:
- The properties are read-only, only properties can be defined.
- Their scope is limited to the method in which they are created.
- Anonymous types cannot be passed as arguments to other methods.
The following example creates a nested anonymous type:
using System;/* j a v a 2 s . c om*/
public class MainClass
{
static void Main(string[] args)
{
var my = new
{
Name = "Jack",
Age = 35,
Address = new
{
Street = "Main Street",
City = "New York"
},
};
// Access the members of the anonymous type.
Console.WriteLine("Name: {0}", my.Name);
Console.WriteLine("Age: {0}", my.Age);
Console.WriteLine("Street: {0}", my.Address.Street);
Console.WriteLine("City: {0}", my.Address.City);
}
}
The output:
Initializing Anonymous Type Arrays
using System;/*from j av a2s .c o m*/
class Program
{
static void Main()
{
var worldCup2006Finalists = new[]{new
{
TeamName = "France",
Players = new string[]
{
"A", "B","C", "D",
}
},
new
{
TeamName = "Italy",
Players = new string[]
{
"Q", "W","E", "R",
}
}
};
Print(worldCup2006Finalists);
}
private static void Print<T>(IEnumerable<T> items)
{
foreach (T item in items)
{
Console.WriteLine(item);
}
}
}
Next chapter...
What you will learn in the next chapter:
- Get to know bool type
- String representing the true and false value
- Output a boolean variable with Console.WriteLine