CODEWITHSUNDEEP
c#loops
Patryk
Patryk

Reputation: 3152

C# // How to make few loops work in the same time?

I've been programming console apps for 1 year and I think its time to start something with forms. I don't really know how to make 2 loops work at the same time.

Could any1 help me and give me an example of 2 loops, working together (1 counting from 1 to 100 and 2nd countin from 100 to 200 (both at the same time, lets say 2 message boxes)). I've been looking for smth like that on the net but without success.

I'd also like to know if infinite whiles has to be like while (5>2) or if theres a better way to do that.

Thanks in advance !

Upvotes: 0

Views: 3656

Answers (4)

ispiro
ispiro

Reputation: 27743

Drop two labels on the form in Designer view. And then add this in Code view:

public Form1()
{
    InitializeComponent();
    Shown += new EventHandler(Form1_Shown);
}

void Form1_Shown(object sender, EventArgs e)
{
    for (int i = 1; i <= 100; i++)
    {
        label1.Text = i.ToString();

        // "Second loop"
        label2.Text = (i + 100).ToString();

        Update();
        System.Threading.Thread.Sleep(10);
    }
}

You'll get two numbers counting simultaneously. One from 1-100. The other from 101-200.

Upvotes: 0

Eric Lippert
Eric Lippert

Reputation: 660513

I don't really know how to make 2 loops work at the same time.

This is a simple question with an enormous answer, but I'll try to break it down for you.

The problem you're describing at its basic level is "I have two different hunks of code that both interact with the user in some way. I would like to give the user the impression that both hunks of code are running at the same time, smoothly responding to user input."

Obviously the easiest way to do that is to write two programs. That is, make the operating system solve the problem. The operating system somehow manages to have dozens of different processes running "at the same time", all interacting smoothly (we hope) with the user.

But having two processes imposes a high cost. Processes are heavyweight, and it is expensive for the two hunks of code to talk to each other. Suppose you therefore want to have the two hunks of code in the same program. Now what do you do?

One way is to put the two hunks of code each on their own thread within the same process. This seems like a good idea, but it creates a lot of problems of its own. Now you have to worry about thread safety and deadlocks and all of that. And, unfortunately, only one thread is allowed to communicate with the user. Every forms application has a "UI" thread. If you have two "worker" threads running your hunks of code, they have to use cross-thread communication to communicate with the UI thread.

Another way is to break up each hunk of code into tiny little pieces, and then schedule all the pieces to run in order, on the UI thread. The scheduler can give priority to user interaction, and any particular tiny piece of work is not going to block and make the UI thread unresponsive.

It is this last technique that I would suggest you explore. We are doing a lot of work in C# 5 to make it easier to write programs in this style.

See http://msdn.microsoft.com/en-us/async for more information about this new feature.

Upvotes: 12

Luke Hutton
Luke Hutton

Reputation: 10722

Not sure if this is what you mean about the two loops.

Infinite loops is anything where while (expression is true) where your expression is 5>2 is always returning true and there is no terminating out of the loop i.e. return; or break;

Upvotes: 0

gabsferreira
gabsferreira

Reputation: 3147

This?

for (int i = 1; i <= 100; i++)
{
    //..
    for (int i2 = 100; i2 <= 200; i2++)
    {
        //..
    }
}

Upvotes: -1

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