Type Inference in c# 3.5

.

 

One of the new language features added in c# 3.0 type inference. its look like a variant data type in vb. But it is not as same as variant in vb. What is type inference is?

Consider the following statements

 

 

int i=10;

 

is equal to

 

var i=10;

 

the compiler  determines what the type of variable is by the value of the variable is initialized to.

 

In the second statement variable is not declared as int. but it is taken as int because the integer value 10 is assigned to int.

 

The compiler will take it as int, as long as it in scope.

 

The variable is here still strongly typed. The var key is valid inside a method.

 

we can not declare class –wide variables with var keywords. the variables declared with var keyword can not have its initial Value as null and also value cannot be a lambda expression, anonymous method or method group (without a cast). For the variables which are declared with var keyword the compile-time type of the value is used for the type of the variable and any further uses of the variable are only checked against the type determined by the initial declaration and assignment.

 

Sample program:

Using System;

 

Class VarSample

{

static void Main(String[] args)

{

 

var item=”idli”;

var price=10;

var isFood=true;

 

Type itemType=item.GetType();

Type priceType=price.GetType();

Type isFoodType=isFood.GetType();

 

Console.WriteLine(“item is type of  “+itemType.ToString());

Console.WriteLine(“price is type of “+priceType.ToString());

Console.WriteLine(“isFood is type of “+isFoodType.ToString());

 

}

}

 

 

Output:

 

Item is type of System.String

Price is type of System.Int32

isFood is type of System.Bool