While Loop in C#

 ## C# `while` Loop: Explanation, Theory, and Examples

### Explanation

A `while` loop in C# is a control flow statement that allows code to be executed repeatedly based on a given boolean condition. The loop continues to execute as long as the condition remains true.

### Theory

The `while` loop consists of two main parts:

1. **Condition**: This boolean expression is evaluated before each iteration of the loop. If the condition is true, the loop body is executed; if false, the loop terminates.

2. **Loop Body**: This is the block of code that is executed repeatedly as long as the condition is true.

The basic syntax of a `while` loop in C# is:

```csharp

while (condition)

{

    // Code to be executed

}

```

### Diagram

Here is a flowchart representing the C# `while` loop:

```

            +--------------------+

            |     Condition      |

            +--------------------+

                     |

                     v

       +-------------+------------+

       |             |            |

       | true        | false      |

       |             v            |

       |     +----------------+   |

       |     |  Execute Code  |   |

       |     +----------------+   |

       |             |            |

       |             v            |

       +-------------+------------+

```

### Examples

#### Example 1: Printing Numbers from 1 to 5

Here is an example of a `while` loop in C# that prints numbers from 1 to 5:

```csharp

using System;

class Program

{

    static void Main()

    {

        int i = 1;

        while (i <= 5)

        {

            Console.WriteLine(i);

            i++;

        }

    }

}

```

**Explanation**:

- **Condition**: `i <= 5;` continues the loop as long as `i` is less than or equal to 5.

- **Loop Body**: `Console.WriteLine(i);` prints the value of `i` and `i++;` increments `i` by 1 after each iteration.

**Output**:

```

1

2

3

4

5

```

#### Example 2: Reading User Input Until "exit" is Entered

Here is an example of a `while` loop in C# that reads user input repeatedly until the user types "exit":

```csharp

using System;

class Program

{

    static void Main()

    {

        string input = "";

        while (input != "exit")

        {

            Console.Write("Enter text (type 'exit' to quit): ");

            input = Console.ReadLine();

            Console.WriteLine("You entered: " + input);

        }

    }

}

```

**Explanation**:

- **Condition**: `input != "exit";` continues the loop as long as the input is not "exit".

- **Loop Body**: `Console.ReadLine();` reads user input and `Console.WriteLine();` prints it.

**Output**:

```

Enter text (type 'exit' to quit): hello

You entered: hello

Enter text (type 'exit' to quit): world

You entered: world

Enter text (type 'exit' to quit): exit

You entered: exit

```

#### Example 3: Summing Numbers Until a Negative Number is Entered

Here is an example of a `while` loop in C# that sums numbers entered by the user until a negative number is entered:

```csharp

using System;

class Program

{

    static void Main()

    {

        int sum = 0;

        int number;

        Console.WriteLine("Enter numbers to sum (negative number to stop):");

        while (true)

        {

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

            if (number < 0) break;

            sum += number;

        }

        Console.WriteLine("Sum: " + sum);

    }

}

```

**Explanation**:

- **Condition**: The loop continues indefinitely (`while (true)`) until a negative number is entered.

- **Loop Body**: `int.Parse(Console.ReadLine());` reads and parses user input, and `sum += number;` adds the number to `sum`.

- **Break**: The loop breaks if a negative number is entered.

**Output**:

```

Enter numbers to sum (negative number to stop):

10

20

-1

Sum: 30

```

### Summary

A `while` loop in C# is a versatile construct that executes a block of code repeatedly based on a given condition. It is used when the number of iterations is not known beforehand, and the loop continues as long as the condition remains true. This makes the `while` loop suitable for scenarios where you need to keep processing data or user input until a specific condition is met.