{"id":189,"date":"2021-12-25T16:09:09","date_gmt":"2021-12-25T09:09:09","guid":{"rendered":"https:\/\/csharptutorial.net\/?page_id=189"},"modified":"2023-07-02T19:17:13","modified_gmt":"2023-07-02T12:17:13","slug":"csharp-for-loop","status":"publish","type":"page","link":"https:\/\/www.csharptutorial.net\/csharp-tutorial\/csharp-for-loop\/","title":{"rendered":"C# for loop"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the C# for loop statement to execute a block repeatedly.<\/p>\n\n\n\n

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

C# for<\/code> statement executes a block while a condition is true<\/code>. The following shows the syntax of the for<\/code> statement:<\/p>\n\n\n

for<\/span>(initializer; condition; iterator)\n{\n    \/\/ statement<\/span>\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
The for<\/code> statement has the following elements initializer<\/code>, condition<\/code>, iterator<\/code>, and the loop body<\/p>\n\n\n\n
initializer<\/h3>\n\n\n\n
The for<\/code> statement executes the initializer<\/code> only once before entering the loop. Typically, you declare and initialize a local loop variable in the initializer. <\/p>\n\n\n\n
Note that if you declare a variable in the initializer, you cannot access it outside the for<\/code> statement.<\/p>\n\n\n\n
condition<\/h3>\n\n\n\n
The condition<\/code> is a boolean expression that determines whether the for<\/code> statement should execute the next iteration. <\/p>\n\n\n\n
The for<\/code> statement evaluates the condition<\/code> before each iteration. If the condition<\/code> is true<\/code> (or is not present), the for<\/code> statement executes the next iteration. Otherwise, it’ll exit the loop.<\/p>\n\n\n\n
iterator<\/h3>\n\n\n\n
The for<\/code> statement executes the iterator<\/code> after each iteration.<\/p>\n\n\n\n
loop body<\/h3>\n\n\n\n
The loop body is inside the curly braces ({}<\/code>) that may consist of one or more statements. If the condition<\/code> is true<\/code> (or not present), the for<\/code> statement executes the loop body in each iteration.<\/p>\n\n\n\n
In the for<\/code> statement, the initializer<\/code>, condition<\/code>, and iterator<\/code> are optional. Therefore, you can have an indefinite for<\/code> loop like this:<\/p>\n\n\n
for<\/span>(;;) \n{\n    \/\/ statement<\/span>\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this case, you need to use the break<\/a><\/code> statement to terminate the loop at some point in time to avoid an indefinite loop<\/strong>.<\/p>\n\n\n\n
The following flowchart illustrates how the for<\/code> loop statement works.<\/p>\n\n\n
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\"c#<\/figure>\n<\/div>\n\n\n
In practice, you’ll use the for<\/code> statement to execute a block a specified number of times<\/strong>.<\/p>\n\n\n\n
C# for loop examples<\/h2>\n\n\n\n
Let’s take some examples of using the for<\/code> loop statement.<\/p>\n\n\n\n
1) A simple C# for loop example<\/h3>\n\n\n\n
The following example uses the for<\/code> statement to output three numbers from zero to two to the console:<\/p>\n\n\n
for<\/span> (int<\/span> i = 0<\/span>; i < 3<\/span>; i++)\n{\n    Console.WriteLine(i);\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
0<\/span>\n1<\/span>\n2<\/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
In the initializer, we declare and initialize the local variable i<\/code>:<\/p>\n\n\n
int<\/span> i = 0<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this condition, we check if the variable i<\/code> is less than three. The condition will determine if the next iteration should run:<\/p>\n\n\n
i < 3<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Since the variable i<\/code> is zero, which is less than three, the for<\/code> statement executes its loop body that outputs the variable i<\/code> to the console:<\/p>\n\n\n
Console.WriteLine(i);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
After the first iteration, the for<\/code> statement runs the iterator that increases the value of the variable i<\/code> by one:<\/p>\n\n\n
i++<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
The i<\/code> variable is 1.<\/p>\n\n\n\n
Starting from the second iteration, the for<\/code> statement doesn’t execute the initializer but only evaluates the condition to determine whether it should continue to the next iteration.<\/p>\n\n\n
i < 3<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Because the variable i<\/code> is one, the condition is true<\/code>. Therefore, the for<\/code> statement executes its loop body the second time that outputs the variable i to the console, and executes the iterator that increases the variable i by one:<\/p>\n\n\n
i++<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
After this, the variable i<\/code> is two. The for<\/code> statement continues checking the condition to determine if it should continue to the next iteration:<\/p>\n\n\n
i < 3<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Because variable i<\/code> is two, the condition is true<\/code>. Therefore, the for<\/code> statement runs the third iteration that outputs the variable i<\/code> to the output and increases the variable i<\/code> by one.<\/p>\n\n\n\n
This time the i<\/code> variable is three that made the condition false<\/code>. Hence, the loop exits.<\/p>\n\n\n\n
In summary, the for<\/code> statement runs its body three times that output three numbers zero, one, and two to the console.<\/p>\n\n\n\n
2) Using the C# for loop to calculate the total of integers from 1 to 10<\/h3>\n\n\n\n
The following example uses the C# for<\/code> statement to calculate the total of integers from 1 to 10:<\/p>\n\n\n
int<\/span> total = 0<\/span>;\nfor<\/span> (int<\/span> i = 1<\/span>; i <= 10<\/span>; i++)\n{\n    total += i;\n\n}\nConsole.WriteLine($\"Total:{total}<\/span>\"<\/span>);<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
Total:55<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, the for<\/code> statement adds the variable i<\/code> to the total<\/code> in each iteration.<\/p>\n\n\n\n
3) Using the C# for loop to display even numbers in the range<\/h3>\n\n\n\n
The following example uses the for<\/code> loop statement to display even numbers between 0<\/code> and 10<\/code>:<\/p>\n\n\n
for<\/span> (int<\/span> i = 0<\/span>; i < 10<\/span>; i++)\n{\n    if<\/span> (i % 2<\/span> == 0<\/span>)\n    {\n        Console.Write($\"{i}<\/span> \"<\/span>);\n    }\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
0<\/span> 2<\/span> 4<\/span> 6<\/span> 8<\/span><\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, the loop body only displays the variable i<\/code> if it is an even number determined by the condition i%2 == 0<\/code>.<\/p>\n\n\n\n
4) Using the C# for loop to display every character of a string<\/h3>\n\n\n\n
The following example uses the for<\/code> statement to display every character of a string:<\/p>\n\n\n
string<\/span> message = \"Hello\"<\/span>;\n\nfor<\/span> (int<\/span> i = 0<\/span>; i < message.Length; i++)\n{\n    Console.WriteLine(message[i]);\n}<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
H\ne\nl\nl\no<\/code><\/span>Code language:<\/span> C#<\/span> (<\/span>cs<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, the string message<\/code> has an index starting from 0<\/code> to message.Length - 1<\/code>.  Therefore, we use the for<\/code> statement to access individual characters of the string by an index in that range.<\/p>\n\n\n\n
Summary<\/h2>\n\n\n\n
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  • Use the for<\/code> loop to execute a block repeatedly for a specified number of times.<\/li>\n<\/ul>\n
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