C# - Loop only when a number changes

Question

Example of my code:

string value = client.DownloadString("http://www.site.com/value.html"); // There is a value of something like a1x6b2xs2 (just one line with random numbers that changes randomly).
Console.WriteLine(value);
Console.ReadKey();

That's all the code! I need to make the console write the number again only if the value in the site got changed! And make it a nonstop loop, just write the number again and again, but only if the old value is changed.

The question is not very clear to me. Did you mean something like : `int newValue = getValueFromHtml(); if (newValue != oldValue) display(); oldValue = newValue;` ? Or did you want to stop checking for differences regularly and be somehow informed that a change in the file occurred (which might or might not be feasible anyway) ? — Loomchild, Oct 24 '12 at 14:53
I just edited the question so if someone can understand it now :P — user1769042, Oct 24 '12 at 15:48
Did you try any of the answers provided? I think most people understood what you were looking for, since everyone gave a similar answer. Even Loomchild. — Bobson, Oct 24 '12 at 16:57

score 7 · Answer 1 · answered Oct 24 '12 at 14:49

7

Why don't you just keep the previous number in a variable and check that before printing?

int previousNumber = int.MinValue; // some invalid value 
while (isRunning) {
    // wait three minutes
    int currentNumber = GetNumberFromSite();
    if (currentNumber != previousNumber) {
        Console.WriteLine(currentNumber);
        previousNumber = currentNumber;
    }
}

answered Oct 24 '12 at 14:49

Botz3000

39,020
8
103
127

7

Surely, it can't be that simple. – Steve Wellens Oct 24 '12 at 14:49

score 1 · Answer 2 · answered Oct 24 '12 at 14:49

You just need to store the old value, and check it before outputting the new one.

int oldVal = -1;

while (true)
{
  int newVal = GetNewValue();
  if (newVal != oldVal)
  {
     Console.WriteLine(newVal);
     oldVal = newVal ;
  }
  Thread.Sleep(1000 * 60 * 3)
}

score 1 · Answer 3 · answered Oct 24 '12 at 14:49

1

Something like this:

int current = ...;
int prev = current;
while(true)
{
    // get new number in current
    if(current != prev) 
        Console.WriteLine(current);
    prev = current;
    // wait 3 min
}

answered Oct 24 '12 at 14:49

Tudor

61,523
12
102
142

score 1 · Answer 4 · answered Oct 24 '12 at 14:50

1

int? oldNumber = null;


// in your loop reading from the website:
if (oldNumber != null && newNumber != oldNumber)
{
    oldNumber = newNumber;
    Console.WriteLine(newNumber);
}

answered Oct 24 '12 at 14:50

Matt Burland

44,552
18
99
171

Ooh, `int?`. Didn't think of that one. Good idea. – Bobson Oct 24 '12 at 14:50

score 0 · Answer 5 · answered Oct 24 '12 at 14:51

You could use a timer that periodically checks whether or not that number has changed.

private System.Threading.Timer checkNumberTimer;
private int currentNumber;

private void InitTimer()
{
    //start immediately, interval is in TimeSpan
    checkNumberTimer = new System.Threading.Timer(
        timer_Elapsed,
        null,
        TimeSpan.Zero,
        Properties.Settings.Default.Interval
    );
}

private void timer_Elapsed(Object state)
{
    int oldNumber = currentNumber;
    currentNumber  =  CheckNumber();
    if( oldNumber != currentNumber  )
        ShowNewNumber( currentNumber );
}

score 0 · Answer 6 · answered Oct 24 '12 at 14:53

0

Write the value to a var, then check if it has changed?

int old, new
new = getValue(file.html)
if new != old then
  write(new) 
old = new

You can translate it to working code yourself.

answered Oct 24 '12 at 14:53

Lodewijk

100
8

C# - Loop only when a number changes

6 Answers6

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