John,
The Do While/ Loop is the same as While/End While. However note that the
alternative syntax of the Do/ Loop While serves a different purpose. See
below:
///
'Condition is checked and only if the condition is satisfied loop is executed
While <condition>
'Do stuff
End While
\\\
///
'Condition is checked after 1st pass through the loop
Do
'Do stuff
Loop While <condition>
\\\
There is no difference. However, note that 'Do...Loop' is much more
flexible than 'While'. In VB6 it was not possible to exit a 'While' loop
using 'Exit While', and thus using 'While' loops made sense because it made
the code more self-documenting. In VB.NET, I never use the 'While' loop
because it's a redundant language feature that doesn't add a value.
Sarika,
Thanks for you response. I was familiar with the difference between Do
While/Loop and Do Loop/While. My question referred to the differende between
the:
While structure and the
Do While/Loop structure
According to the text I am reading, they are the same.
But if that is really (100%) so, why do they both exist?
Thanks for you response. I was familiar with the difference between Do
While/Loop and Do Loop/While. My question referred to the differende
between
the:
While structure and the
Do While/Loop structure
According to the text I am reading, they are the same.
But if that is really (100%) so, why do they both exist?
They exist because BASIC had two types of loops: 'Do...Loop' loops which
allowed 'Until' and 'While' end coditions in the head and the tail of the
block and a way to exit the loop and the 'While...Wend' loop which supported
a 'While' condition in its head only and didn't provide a command to exit
the loop. In VB.NET, 'Wend' has been renamed to 'End While' and 'Exit
While' has been added.
:
: What is the difference between a While and Do While/Loop repetition
: structure. If they is no difference (as it seems) why do both exist?
The two constructs are very similar and often achieve the same results:
Dim i As Integer = 3
While i > 0
i = i - 1
Console.WriteLine("In the While loop")
End WHile
However, you have more flexibility with the Do/Loop structure. You can
use a Do While or a Do Until statement that may be clearer. The code is
essentially the same but one may be more appropriate than the other (it
is often a question of personal style more than anything else).
Do While i > 0
i = i - 1
Console.WriteLine("In the Do While loop")
Loop
Do Until i <= 0
i = i - 1
Console.WriteLine("In the Do Until loop")
Loop
However, the real benefit of a Do / Loop is that you can delay the
conditional until the Loop runs at least once. In the examples above, if
i was set to an initial value of 0, you'd never hit the
Console.WriteLine statement. In the following example however, you will
always process that line at least once:
Do
i = i - 1
Console.WriteLine("In the Do loop")
Loop Until i < 1
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