C# - Type Conversion (Type Casting)

Type conversion in C# means converting one data type into another. It is also known as type casting. There are mainly two types of type casting in C#: implicit type conversion and explicit type conversion.

1. Implicit Type Conversion

Implicit type conversion is automatically handled by the C# compiler. It happens when the conversion is safe and no data will be lost. This usually includes conversions from a smaller data type to a larger data type, such as from int to double, or from a derived class to a base class.

For example:
If we have an integer variable a with value 9, and we assign it to a double variable b, the compiler automatically converts it.

int a = 9;

double b = a;

Here, a is automatically converted to a double type. When we print both values using Console.WriteLine, the output will be:

9

9

 

2. Explicit Type Conversion

Explicit type conversion, also known as manual casting, is done by the programmer using a cast operator. This type of conversion is used when converting from a larger data type to a smaller one, or between incompatible types. It can result in data loss.

For example:
If we have a double variable a with value 9.78, and we want to convert it into an integer:

double a = 9.78;

int b = (int)a;

In this case, we are manually converting a to an integer by placing (int) in front of the variable. This will cut off the decimal part and the output will be:

9.78

9

 

3. Type Conversion Using Built-in Methods

C# provides a set of built-in methods in the Convert class for converting between data types. These methods allow safe and easy conversions between types like int, string, double, boolean, etc.

Some commonly used methods include:

• Convert.ToString() – converts any value to a string.
• Convert.ToDouble() – converts a value to a double.
• Convert.ToInt32() – converts a value to a 32-bit integer.
• Convert.ToBoolean() – converts a value to a boolean.

Example:

int a = 20;

double e = 2.25;

bool b = true;

 

Console.WriteLine(Convert.ToString(a));     // Outputs "20"

Console.WriteLine(Convert.ToDouble(a));     // Outputs 20.0

Console.WriteLine(Convert.ToInt32(e));      // Outputs 2

Console.WriteLine(Convert.ToString(b));     // Outputs "True"

 

 4. Using Int32.Parse() Method

In addition to the Convert class, we can also use the Parse() method to convert a string to an integer. The string must be a valid numeric value.

Example:

string input = "123";

int result = Int32.Parse(input);

Console.WriteLine(result);

This will convert the string "123" into the integer 123.

 

Complete Program Example: Converting int to String and Double

Here is a complete program that demonstrates how to convert an integer into a string and a double using the Convert class.

using System;

 

namespace Conversion {

  class Program {

    static void Main(string[] args) {

 

      int num = 100;

      Console.WriteLine("int value: " + num);

 

      // Convert int to string

      string str = Convert.ToString(num);

      Console.WriteLine("string value: " + str);

 

      // Convert int to double

      double doubleNum = Convert.ToDouble(num);

      Console.WriteLine("Double value: " + doubleNum);

 

      Console.ReadLine();

    }

  }

}

Output:

int value: 100 

string value: 100 

Double value: 100 

Operators in C#

In C#, operators are symbols that perform operations on variables and values, forming the basis of expressions and enabling various computations and comparisons.

 1. Arithmetic Operators
Arithmetic operators are used to perform mathematical operations such as addition, subtraction, multiplication, and division.

Operator	Name	What It Does	Example
+	Addition	Adds two numbers	a + b
-	Subtraction	Subtracts one number from another	a - b
*	Multiplication	Multiplies two numbers	a * b
/	Division	Divides one number by another	a / b
%	Modulus	Gives the remainder of division	a % b

Use: For doing calculations like total marks, average, or price after discount.

 

 2. Comparison (Relational) Operators

Comparison operators are used to compare two values and return either true or false.

Operator	Name	What It Does	Example
==	Equal to	Checks if two values are equal	a == b
!=	Not equal to	Checks if two values are not equal	a != b
>	Greater than	Checks if one value is more than another	a > b
<	Less than	Checks if one value is less than another	a < b
>=	Greater or equal	Checks if one value is more or equal	a >= b
<=	Less or equal	Checks if one value is less or equal	a <= b

Use: When making decisions like checking age, marks, or eligibility.

 

3. Logical Operators

Logical operators are used to combine two or more conditions and return a true or false result.

Operator	Name	What It Does	Example
&&	AND	Returns true only if both conditions are true	a > 5 && b < 10
!	NOT	Reverses the result: true becomes false, and vice versa	!(a > 5)

Use: Used in if conditions, like checking if a student passed and attended class.

 4. Assignment Operators

Assignment operators are used to assign values to variables, and also to update them.

Operator	Name	What It Does	Example
=	Assign	Stores a value in a variable	a = 5
+=	Add and assign	Adds value to variable	a += 5
-=	Subtract and assign	Subtracts value from variable	a -= 3
*=	Multiply and assign	Multiplies variable by a value	a *= 2
/=	Divide and assign	Divides variable by a value	a /= 4
%=	Modulus and assign	Stores remainder in the variable	a %= 2

Use: Helpful for updating scores, totals, or counts in programs.

 

5. Unary Operators

Unary operators work with a single variable to change its value or state.

Operator	Name	What It Does	Example
+	Positive	Keeps the number positive	+a
-	Negative	Changes the number to negative	-a
++	Increment	Adds 1 to the value	a++ or ++a
--	Decrement	Subtracts 1 from the value	a-- or --a
!	Logical NOT	Reverses a boolean value	!true is false

Use: Often used for counters, like increasing marks or flipping boolean values.

6. Bitwise Operators (Advanced)

Bitwise operators are used to work with bits (0s and 1s) of integer values.

Operator	Name	What It Does	Example
&	Bitwise AND	Compares bits and returns 1 if both are 1	a & b
`	`	Bitwise OR	Compares bits and returns 1 if any is 1
^	Bitwise XOR	Returns 1 if only one is 1	a ^ b
~	Bitwise NOT	Flips the bits (0 becomes 1, 1 becomes 0)	~a
<<	Left shift	Shifts bits to the left	a << 2
>>	Right shift	Shifts bits to the right	a >> 2

Use: Used in lower-level programming, like controlling hardware or optimizing memory.

7.  Conditional Operator (Ternary)

A shortcut for if-else that chooses one value based on a condition.

Operator	Name	What It Does	Example
?:	Ternary	Returns one of two values based on a condition	max = (a > b) ? a : b;

Use: For quick decisions like checking which number is greater.

C# Input for Different Data Types

The simplest way to get input from the user is by using the ReadLine() method of the Console class. However, the Read() and ReadKey() methods are also available for getting user input. All three methods are part of the Console class.

In C#, all user input from the console is initially taken as a string using Console.ReadLine(). To use it as another data type, you must convert it using methods like Convert.ToInt32(), Convert.ToDouble(), etc.

 1. String Input

Console.Write("Enter your name: ");

string name = Console.ReadLine();

Console.WriteLine("Hello " + name);

 

2. Integer (int) Input

Console.Write("Enter your age: ");

int age = Convert.ToInt32(Console.ReadLine());

Console.WriteLine("Age: " + age);

Alternative:

int age = int.Parse(Console.ReadLine());

 

3. Float Input

Console.Write("Enter your height in meters: ");

float height = float.Parse(Console.ReadLine());

Console.WriteLine("Height: " + height);

Note: float.Parse() may need f at the end when assigning values directly (e.g., 1.75f), but not from input.

 

4. Double Input

Console.Write("Enter your GPA: ");

double gpa = Convert.ToDouble(Console.ReadLine());

Console.WriteLine("GPA: " + gpa);

 

 5. Boolean (bool) Input

Console.Write("Are you a student? (true/false): ");

bool isStudent = Convert.ToBoolean(Console.ReadLine());

Console.WriteLine("Student: " + isStudent);

---

Character (char) Input

Console.Write("Enter a character: ");

char ch = Convert.ToChar(Console.ReadLine());

Console.WriteLine("Character: " + ch);

Alternatively, using ReadKey():

Console.Write("Press a key: ");

char ch = Console.ReadKey().KeyChar;

 

Difference between ReadLine(), Read() and ReadKey() method:

Method	What it does	Return Type	Example Use
Read()	Reads a single character as ASCII (int)	int	int ch = Console.Read();
ReadLine()	Reads the entire line of text	string	string name = Console.ReadLine();
ReadKey()	Reads a single key press	ConsoleKeyInfo	ConsoleKeyInfo key = Console.ReadKey();