Thursday, September 11, 2008

loop structures

Loop Structures
Visual Basic loop structures allow you to run one or more lines of code repetitively. You can repeat the statements in a loop structure until a condition is True, until a condition is False, a specified number of times, or once for each element in a collection.
The following illustration shows a loop structure that runs a set of statements until a condition becomes true.
Running a set of statements until a condition becomes true.

While Loops
The While...End While construction runs a set of statements as long as the condition specified in the While statement is True. For more information, see While...End While Statement (Visual Basic).
Do Loops
The Do...Loop construction allows you to test a condition at either the beginning or the end of a loop structure. You can also specify whether to repeat the loop while the condition remains True or until it becomes True. For more information, see Do...Loop Statement (Visual Basic).
For Loops
The For...Next construction performs the loop a set number of times. It uses a loop control variable, also called a counter, to keep track of the repetitions. You specify the starting and ending values for this counter, and you can optionally specify the amount by which it increases from one repetition to the next. For more information, see For...Next Statement (Visual Basic).