For Next Loop is used to repeatedly execute a sequence of code or a block of code until a given condition is satisfied. It is useful in such a case when we know how many times a block of code has to be executed.
You use a
For Next Loop when you want to repeat some statements a set number of times.
In the following example, the
index variable starts with a value of 1 and is incremented with each iteration of the loop, ending after the value of the
index reaches 10.
Public Sub Example1() For index As Integer = 1 To 10 Console.Write(index.ToString & ", ") Next Console.WriteLine("") End Sub
Let's consider another example in which the
number variable starts at 5 and is reduced by 0.5 on each iteration of the loop, ending after the value of
number reaches 0. The
Step argument of -.5 reduces the value by 0.5 on each iteration of the loop.
Public Sub Example2() For number As Double = 5 To 0 Step -0.5 Console.Write(number.ToString & ", ") Next Console.WriteLine("") End Sub
You can also nest
For Next loops by putting one loop within another.
The following example shows nested
For Next loops that have different step values.
Public Sub Example3() For indexA = 1 To 3 Dim sb As New System.Text.StringBuilder() For indexB = 20 To 1 Step -2 sb.Append(indexB.ToString) sb.Append(" ") Next indexB Console.WriteLine(sb.ToString) Next indexA End Sub
The outer loop creates a string for every iteration of the loop. The inner loop decrements a loop counter variable for every iteration of the loop.
When nesting loops, each loop must have a unique counter variable.
Exit For statement immediately exits the
For Next loop and transfers control to the statement that follows the
Continue For statement transfers control immediately to the next iteration of the loop.
The following example shows the use of the
Continue For and
Exit For statements.
Public Sub Example4() For index As Integer = 1 To 100000 If index >= 5 AndAlso index <= 8 Then Continue For End If Console.Write(index.ToString & " ") ' If index is 10, exit the loop. If index = 10 Then Exit For End If Next Console.WriteLine("") End Sub
You can put any number of
Exit For statements in a
For Next loop. When used within nested
For Next loops,
Exit For exits the innermost loop and transfers control to the next higher level of nesting.
Exit For is often used after you evaluate some condition such as an