Variance in C# 4.0
Posted On Monday, May 25, 2009 at
at
7:35 PM
by test
Variance is of two types
1: Covariance
2: ContraVariance
It used to be that an IEnumerable/
The C# compiler allows you to call a method with any name and any arguments on d because it is of type dynamic. At runtime the actual object that d refers to will be examined to determine what it means to “call M with an int” on it.
The type dynamic can be thought of as a special version of the type object, which signals that the object can be used dynamically. It is easy to opt in or out of dynamic behavior: any object can be implicitly converted to dynamic, “suspending belief” until runtime. Conversely, there is an “assignment conversion” from dynamic to any other type, which allows implicit conversion in assignment-like constructs:
dynamic d = 7; // implicit conversion
int i = d; // assignment conversion
Complete Example for variance
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LearnVarianceUse
{
class Shape { }
class Square: Shape { }
class Program
{
// Declaring delegates
delegate T Func1();
delegate void Action1(T a);
static void Main(string[] args)
{
// Creating the funcSquare function which takes no parameters , see empty ()
Func1 funcSquare = () => new Square();
// Assigning the funcSquare to funcShape type Func and it is variance which is possible only in c#4.0
// it gives compile time error in c#3.0
Func1 funcShape = funcSquare;
/*
* In the next line, we are creating a function which is called by delegate and , we
* are passing someobject which is simply printed on the console.
* */
Action1 actionShape = (objParameter) => { Console.WriteLine(objParameter); };
/* In Next line, We are assigning the actionShape Type delegate to the
* actionSquare type which was not allowed in c#3.0 but now it is possible to
* use this variance , you can use base type of delegate to inherited
* type
* */
Action1 actionSquare = actionShape;
Console.WriteLine(funcShape());
actionShape(new Shape()); // same type of object is used
actionShape(new Square()); // inherited type of object is used
Console.ReadLine();
}
}
}
if you have any queries , please email me.
Happy Coding.
1: Covariance
2: ContraVariance
It used to be that an IEnumerable/
The C# compiler allows you to call a method with any name and any arguments on d because it is of type dynamic. At runtime the actual object that d refers to will be examined to determine what it means to “call M with an int” on it.
The type dynamic can be thought of as a special version of the type object, which signals that the object can be used dynamically. It is easy to opt in or out of dynamic behavior: any object can be implicitly converted to dynamic, “suspending belief” until runtime. Conversely, there is an “assignment conversion” from dynamic to any other type, which allows implicit conversion in assignment-like constructs:
dynamic d = 7; // implicit conversion
int i = d; // assignment conversion
Complete Example for variance
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LearnVarianceUse
{
class Shape { }
class Square: Shape { }
class Program
{
// Declaring delegates
delegate T Func1
delegate void Action1
static void Main(string[] args)
{
// Creating the funcSquare function which takes no parameters , see empty ()
Func1
// Assigning the funcSquare to funcShape type Func and it is variance which is possible only in c#4.0
// it gives compile time error in c#3.0
Func1
/*
* In the next line, we are creating a function which is called by delegate and , we
* are passing someobject which is simply printed on the console.
* */
Action1
/* In Next line, We are assigning the actionShape Type delegate to the
* actionSquare type which was not allowed in c#3.0 but now it is possible to
* use this variance , you can use base type of delegate to inherited
* type
* */
Action1
Console.WriteLine(funcShape());
actionShape(new Shape()); // same type of object is used
actionShape(new Square()); // inherited type of object is used
Console.ReadLine();
}
}
}
if you have any queries , please email me.
Happy Coding.
Posted in
Labels:
C#
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