Continue

The continue statement is used to jump back to the condition of the current loop. This can be very useful for skipping the processing of the current loop, while allowing the loop to continue for another cycle. See a visualisation of this in the image below.

The continue statement allows you to jump to the condition, skipping the remainder of the code in the loop but allowing the loop to continue

Continue — when, why, and how?

Like break, the continue statement isn’t something you use often. Most of the time you will want to execute the entire body of a loop. However, when needed you can use continue skip an iteration. This is typically done by using continue within a branching statement.

When you use continue in a for loop, the post-loop increment will still be executed to ensure that you move to the next value in the control variable. In a while loop, you need to make sure you have updated the condition before the continue statement so that you do not end up in an infinite loop.

In C#

The continue statement is simply the continue keyword terminated by a semicolon (;).

How does continue work?

Skipping iterations in a for loop

The following code loops from 0 to 10, skipping all loops where i is larger than 0 and divisible by 3. Therefore, this will print 0, 1, 2, 4, 5, 7, 8, and 10 (skipping 3, 6, and 9).

using static System.Console;
using static System.Convert;

for (int i = 0; i < 11; i++)
{
    if( i > 0 && i % 3 == 0)
    {
        continue;
    }
    WriteLine(i);
}

The following images show how this works.

Line 1 begins the for loop which initializes the variable 'i' to 0 (step 1a), then tests the condition (which evaluates to true). Control moves to line 3.

The first condition in the 'if' statement evaluates to false, and the program counter jumps to line 7 without executing the body of the 'if' statement

Line 7 prints the value of the variable 'i' to the terminal (0) then moves back to the for loop at line 1

Step 1c increments the variable i from 0 to 1, then step 1b tests the for loop condition which evaluates to true since 1 is less than 11

The first condition in the 'if' statement evaluates to true but the second condition to false, so the entire condition is false. The program counter jumps to line 7 without executing the body of the 'if' statement

Line 7 prints the value of the variable 'i' to the terminal (1) then moves back to step 1c of the for loop at line 1

Step 1c increments the variable i from 1 to 2, then step 1b tests the for loop condition which evaluates to true since 2 is less than 11

The condition in the 'if' statement evaluates to false since 2%3 equals 2. The program counter jumps to line 7 without executing the body of the 'if' statement

Line 7 prints the value of the variable 'i' to the terminal (2) then moves back to the for loop at line 1

Step 1c increments the variable i from 2 to 3, then step 1b tests the for loop condition which evaluates to true since 2 is less than 11

This time the condition in the 'if' statement evaluates to true since i(3) is greater than zero and 3%3 equals 0

The continue statement instructs the CPU to >skip any remaining code in this iteration of the for loop by jumping to the next iteration of the loop at line 1

Step 1c increments the variable i from 3 to 4, then step 1b tests the for loop condition which evaluates to true since 4 is less than 11

The condition in the 'if' statement evaluates to false since 4%3 equals 1. The program counter jumps to line 7 without executing the body of the 'if' statement

Line 7 prints the value of the variable 'i' to the terminal (4) then moves back to the for loop at line 1

Let's jump ahead - the loop continues in the same manner printing the numbers 0,1,2,4,5,7,8,10. Now when the variable 'i' is incremented from 10 to 11, the condition at step 1c evaluates to false, and the for loop ends.

Skipping iterations in a while loop

The following example is functionally the same as the previous, just using a while loop instead of a for loop. Note that this code also has an increment (i++) in the if statement. This makes sure that even when continue is executed the loop counter is incremented so that our code does not have an infinite loop. See if you can step through this code yourself and understand how it works the same way as the for loop above.

using static System.Console;
using static System.Convert;

int i = 0;

while (i < 11)
{
    if ( i > 0 && i % 3 == 0 )
    {
        i++;
        continue;
    }

    WriteLine(i);
    i++;
}