{"id":184,"date":"2021-12-24T14:14:43","date_gmt":"2021-12-24T07:14:43","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=184"},"modified":"2023-07-02T19:09:30","modified_gmt":"2023-07-02T12:09:30","slug":"csharp-do-while","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-tutorial\/csharp-do-while\/","title":{"rendered":"C# do while"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the C# do while<\/code> statement to execute a block of code repeatedly as long a condition is true<\/code>.<\/p>\n\n\n\n

Introduction to the C# do while statement<\/h2>\n\n\n\n

The C# do while<\/code> statement executes one or more iterations as long as a condition is true<\/code>.<\/p>\n\n\n\n

The following shows the syntax of the do while<\/code> statement:<\/p>\n\n\n

do<\/span>\n{\n    \/\/ statement<\/span>\n} while<\/span> (expression);<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Unlike the while<\/a><\/code> statement, the do while<\/code> statement checks the expression<\/code> at the end of each iteration. Therefore, it’s called a posttest loop.<\/p>\n\n\n\n
The do while<\/code> statement will always run the first iteration regardless of the expression’s result. And it’ll execute the block repeatedly as long as the expression is true<\/code>.<\/p>\n\n\n\n
Inside the loop, you need to change some variables to make the expression false<\/code> so that the loop will terminate after some iterations. Otherwise, you’ll have an indefinite loop.<\/p>\n\n\n\n
The following flowchart illustrates how the do while<\/code> statement works:<\/p>\n\n\n
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\"C#<\/figure>\n<\/div>\n\n\n
C# do while statement examples<\/h2>\n\n\n\n
Let’s take some examples of using the do while<\/code> statement.<\/p>\n\n\n\n
1) Simple C# do while statement example<\/h3>\n\n\n\n
The following example shows how to use the do while<\/code> statement to print out five numbers from 1 to 5:<\/p>\n\n\n
int counter = 0<\/span>;\ndo<\/span>\n{\n    counter++;\n    Console.WriteLine(counter);\n\n} while<\/span> (counter < 5<\/span>);<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
1\n2\n3\n4\n5<\/code><\/span><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
First, declare the counter<\/code> variable and initialize its value to 0.<\/p>\n\n\n\n
Second, increase the counter<\/code> by one and display it in the do while<\/code> block. Repeat this step as long as the counter<\/code> is less than 5. Since the counter<\/code> starts at one, the do while<\/code> statement executes exactly five times.<\/p>\n\n\n\n
2) Using the do-while statement to create a guessing game<\/h3>\n\n\n\n
The following illustrates how to use the do while<\/code> statement to create the “Guess the Number” game. The program will generate a random number between 1 and 10. <\/p>\n\n\n\n
And you’ll have a maximum of 4 turns. If your guess is higher or lower than a secret number, you’ll get a hint:<\/p>\n\n\n
int guess = 0<\/span>, yourNumber;\nstring hint;\n\n\n\/\/ Get a random number between 1 and 10<\/span>\nint secretNumber = (new<\/span> Random()).Next(1<\/span>, 10<\/span>);\n\nConsole.WriteLine(\"Pick a number between 1 and 10. You'll have 4 turns.\"<\/span>);\ndo<\/span>\n{\n    guess++;\n\n    \/\/ Get the user input<\/span>\n    Console.Write($\"Turn #{guess}. Your number:\"<\/span>);\n    yourNumber = Convert.ToInt32(Console.ReadLine());\n\n    \/\/ Check the input number with the secret number<\/span>\n    if<\/span> (yourNumber < secretNumber)\n    {\n        hint = $\"Your guess: {yourNumber}, which is too low.\"<\/span>;\n    }\n    else<\/span> if<\/span> (yourNumber > secretNumber)\n    {\n        hint = $\"Your guess: {yourNumber}, which is too high.\"<\/span>;\n    }\n    else<\/span>\n    {\n        hint = $\"Bingo! It took you {guess} turns to guess the secret number {secretNumber}.\"<\/span>;\n    }\n    Console.WriteLine(hint);\n\n} while<\/span> (guess < 4<\/span> && yourNumber != secretNumber);\n\n\nif<\/span> (yourNumber != secretNumber)\n{\n    Console.WriteLine(\"Oops! you lost.\"<\/span>);\n}\n<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
First, declare the guess<\/code> variable to store the number of guesses and yourNumber<\/code> variable to store the input number:<\/p>\n\n\n
int guess = 0, yourNumber;<\/code><\/span><\/pre>\n\n\n
Second, get a random integer between 1 and 10:<\/p>\n\n\n
int secretNumber = (new<\/span> Random()).Next(1<\/span>, 10<\/span>);<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
This code creates a new instance of the Random<\/code> class and call the Next()<\/code> method to generate a random number between 1 and 10. Note that you’ll learn more about classes and methods in the later tutorial.<\/p>\n\n\n\n
Third, show the message on the screen:<\/p>\n\n\n
Console.WriteLine(\"Pick a number between 1 and 10. You'll have 4 turns.\"<\/span>);<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Fourth, use the do while<\/code> statement to get the user’s input number. <\/p>\n\n\n\n
The loop will continue if the number of guesses is less than 4 and the input number is different from the secret number. <\/p>\n\n\n\n
Inside the do while<\/code> loop:<\/p>\n\n\n\n
1) Increase the value of the guess<\/code> variable by one in each iteration:<\/p>\n\n\n
guess++;<\/code><\/span><\/pre>\n\n\n
2) Get the input number:<\/p>\n\n\n
Console.Write($\"Turn #{guess}. Your number:\"<\/span>);\nyourNumber = Convert.ToInt32(Console.ReadLine());<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
3) Check the input number with the secret number and give a hint if the input number is lower or higher. Also, print a message if the input number equals the secret number:<\/p>\n\n\n
if<\/span> (yourNumber < secretNumber)\n{\n    Console.WriteLine($\"Your guess: {yourNumber}, which is too low.\"<\/span>);\n}\nelse<\/span> if<\/span> (yourNumber > secretNumber)\n{\n    Console.WriteLine($\"Your guess: {yourNumber}, which is too high.\"<\/span>);\n}\nelse<\/span>\n{\n    Console.WriteLine($\"Bingo! It took you {guess} turns to guess the secret number {secretNumber}.\"<\/span>);\n}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
Finally, print a message if the input number is not equal to the secret number:<\/p>\n\n\n
if<\/span> (yourNumber != secretNumber)\n{\n    Console.WriteLine(\"Oops! you lost.\"<\/span>);\n}<\/code><\/span>Code language:<\/span> JavaScript<\/span> (<\/span>javascript<\/span>)<\/span><\/small><\/pre>\n\n\n
The following shows a test:<\/p>\n\n\n
Pick a number between 1 and 10. You'll have 4 turns.\nTurn #1. Your number:5\nYour guess: 5, which is too low.\nTurn #2. Your number:6\nYour guess: 6, which is too low.\nTurn #3. Your number:7\nYour guess: 7, which is too low.\nTurn #4. Your number:8\nBingo! It took you 4 turns to guess the secret number 8.<\/code><\/span><\/pre>\n\n\n
Summary<\/h2>\n\n\n\n
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  • Use the do while<\/code> statement to execute a block of code repeatedly as long as a condition is true.<\/li>\n<\/ul>\n
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