{"id":178,"date":"2021-12-24T11:17:21","date_gmt":"2021-12-24T04:17:21","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=178"},"modified":"2023-07-02T19:06:07","modified_gmt":"2023-07-02T12:06:07","slug":"csharp-while","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-tutorial\/csharp-while\/","title":{"rendered":"C# while"},"content":{"rendered":"\n

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

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

The while<\/code> statement evaluates a boolean expression and executes a block repeatedly as long as the expression is true<\/code>. Here’s the syntax of the while<\/code> statement:<\/p>\n\n\n

while<\/span> (expression)\n{\n    \/\/ statement<\/span>\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
The expression<\/code>, which follows the while<\/code> keyword, must be a boolean expression that evaluates to true<\/code> or false<\/code>.<\/p>\n\n\n\n
The while<\/code> statement evaluates the expression<\/code> first. If the expression<\/code> evaluates to true<\/code>, it’ll execute the block inside the curly braces.<\/p>\n\n\n\n
Once completed executing the block, the while<\/code> statement checks the expression<\/code> again. And it’ll execute the block again as long as the expression<\/code> is true<\/code>.<\/p>\n\n\n\n
If the expression<\/code> is false<\/code>, the while<\/code> statement exits and passes the control to the statement after it.<\/p>\n\n\n\n
Therefore, you need to change some variables<\/a> inside the block to make the expression<\/code> false<\/code> at some point. Otherwise, you’ll have an indefinite loop<\/strong>.<\/p>\n\n\n\n
Since the expression<\/code> is checked at the beginning of each iteration, the while<\/code> statement is often called a pretest loop.<\/p>\n\n\n\n
The following flowchart illustrates how the C# while statement works.<\/p>\n\n\n
\n
\"c#<\/figure>\n<\/div>\n\n\n
C# while statement examples<\/h2>\n\n\n\n
Let’s take some examples of using the while<\/code> statement.<\/p>\n\n\n\n
1) Simple C# while statement example<\/h3>\n\n\n\n
The following example uses the while<\/code> loop statement to output five numbers from 1 to 5 to the console:<\/p>\n\n\n
int<\/span> counter = 0<\/span>;\n\nwhile<\/span>(counter < 5<\/span>)\n{\n    counter++;\n    Console.WriteLine(counter);\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
1<\/span>\n2<\/span>\n3<\/span>\n4<\/span>\n5<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
First, declare a counter<\/code> variable and initialize it to zero.<\/p>\n\n\n\n
Second, enter the while<\/code> loop because the following expression is true<\/code>:<\/p>\n\n\n
counter < 5<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Third, increase the counter<\/code> by one and print it out to the console; repeat this step as long as the counter<\/code> is less than 5. <\/p>\n\n\n\n
2) Using the C# while statement to calculate the average<\/h3>\n\n\n\n
The following program prompts users to enter a list of numbers and calculate the average:<\/p>\n\n\n
double<\/span> number = 0<\/span>,\n    total = 0<\/span>,\n    count = 0<\/span>,\n    average = 0<\/span>;\n\nstring<\/span> input = \"\"<\/span>;\n\n\nConsole.WriteLine(\"Enter a list of numbers to calculate the average (Q - quit):\"<\/span>);\n\nwhile<\/span> (input != \"Q\"<\/span> && input != \"q\"<\/span>)\n{\n    input = Console.ReadLine();\n    if<\/span> (input != \"Q\"<\/span> && input != \"q\"<\/span>)\n    {\n        number = Convert.ToDouble(input);\n        total += number;\n        count++;\n    }\n}\n\nif<\/span> (count > 0<\/span>)\n{\n    average = total \/ count;\n}\n\nConsole.WriteLine($\"Average:{average}<\/span>\"<\/span>);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
First, declare variables and initialize them:<\/p>\n\n\n
double<\/span> number = 0<\/span>,\n    total = 0<\/span>,\n    count = 0<\/span>,\n    average = 0<\/span>;\n\nstring<\/span> input = \"\"<\/span>;<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Second, print out the instruction:<\/p>\n\n\n
Console.WriteLine(\"Enter a list of numbers to calculate the average (Q - quit):\"<\/span>);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Third, prompt users to enter a number until they enter the letter Q<\/code> or q<\/code>. In each iteration, calculate the total and count the entered numbers:<\/p>\n\n\n
while<\/span> (input != \"Q\"<\/span> && input != \"q\"<\/span>)\n{\n    input = Console.ReadLine();\n    if<\/span> (input != \"Q\"<\/span> && input != \"q\"<\/span>)\n    {\n        number = Convert.ToDouble(input);\n        total += number;\n        count++;\n    }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Finally, calculate the average if users enter at least one number and output it to the console:<\/p>\n\n\n
if<\/span> (count > 0<\/span>)\n{\n    average = total \/ count;\n}\nConsole.WriteLine($\"Average:{average}<\/span>\"<\/span>);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In the following output, we enter three numbers 10, 20, and 30. And the program shows the average as 20:<\/p>\n\n\n
Enter a list of numbers to calculate the average<\/span> (Q - quit<\/span>):\n10\n20\n30\nq\nAverage:20<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary<\/h2>\n\n\n\n
    \n
  • Use the while<\/code> statement to execute a block as long as a boolean expression is true<\/code>.<\/li>\n<\/ul>\n
    \n\t
    \n\t\t
    Was this tutorial helpful ?<\/div>\n\t\t
    \n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t
    \n\t\t
    \n\t\t\t
    <\/div>\n\t\t\t\n\t\t\t