Re: Kill execute function - C# Discussion Boards

21-Dec-18 1:01

Why? He'll only make mistakes, which you need to check for.
Instead of a textbox, use a Combobox and he can only give you valid values:
On startup:

cbDefinitions.DataSource = Enum.GetValues(typeof(DEFINITION));

And when you want a value:

DEFINITION userSelected = (DEFINITION)cbDefinitions.SelectedItem;
Transmit(userSelected);

No strings, no switch to find out which he used and convert it to your enum, no errors.

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Re: ENUM value in method

Richard Deeming21-Dec-18 1:13

21-Dec-18 1:13

As Griff said, the user is going to make mistakes. But if you really need to stick with a textbox, then you'll need to use the Enum.TryParse[^] method:

DEFINITION definition;
if (Enum.TryParse(YourTextBox.Text, true, out definition))
{
    Transmit(definition);
}
else
{
    ... Show an error message to the user ...
}

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

Kill execute function

MatrixRatrix20-Dec-18 5:50

20-Dec-18 5:50

Hello,

I need kill a function by press button,

I have a function (method) ex:

public void move()
  {
      int count = 0;
      while(true)
      {
          count++;
      }
  }

I need kill this method by when press button.

Any Idea?

thanks

Richard Deeming20-Dec-18 6:01

20-Dec-18 6:01

Assuming you're running that on the UI thread, you won't be able to press the button to stop it. The entire UI will be frozen.

If it's running on a background thread, then you should be able to use a CancellationTokenSource[^] to coordinate cancelling the loop.

However, you've simplified your code to the point where it's not actually doing anything. Perhaps if you explain what you're actually trying to do, we might be able to provide better help. Smile | :)

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

MatrixRatrix20-Dec-18 7:09

20-Dec-18 7:09

Thank you for the replay,

No, is not a Thread while loop, is a normal method with while loop.

So, I'll try to explain my idea.

I will try to explain my function, it is not exactly what I posted, I just collided so to simplify the explanation.

I have this button that run a method:

private void btn_move_Click(object sender, EventArgs e)
{

    while (true)
    {

    SnapFunction();

    }
}

This "SnapFunction" have (wait for something) so, this function stay stop until the condition is true,
and wend condition is true, the code make another cycle until waint again for the condition is true.

Basically the condition is waits until something in the form is selected by the mouse, but this
code stay paused on the line.

What I need is, stop this function by some way.

Richard Deeming20-Dec-18 8:09

20-Dec-18 8:09

As I said, you're running that on the UI thread. Therefore, the UI is frozen, and cannot respond to any input from the user.

You could possibly use something like this: Fun with Rx[^]

Or something like this: WinForms and TPL - Achieving quick Multitasking and Responsive User Interface[^]

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

OriginalGriff20-Dec-18 8:20

20-Dec-18 8:20

You can't, not at all.
When you loop in any UI control event handler, the thread that handles them all is busy running the loop until the event handler method exits - which it never does because it is sitting in your loop!

Loops in event handlers are - with exceptions - a bad idea, and loops in UI handlers are a very bad idea because they prevent any other event being recognized and processed because the only thread which is allowed to access UI controls (called the "UI thread") is permanently busy processing a single event.

If you want to use any form of user input to terminate a loop, the loop must be running on a different thread - which means you manually starting another thread and setting the loop running. That's not difficult to do (the BackgroundWorker Class (System.ComponentModel) | Microsoft Docs[^] makes it pretty painless and provides a simple way for your new thread to report progress / results to the user) but it is an operation that you have to start yourself, the system will not do it for you!

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OriginalGriff20-Dec-18 6:06

c# listview Update problem

20-Dec-18 6:06

You can't kill "a method" from outside. You can kill the thread it is being executed on, but ... you can't tell that the thread is executing the function!

What you need is a semaphore that is checked in the method instead of the while(true), and signaled elsewhere in your app to indicate the method should exit when ready.

See here: How to: Create and Terminate Threads (C# Programming Guide) | Microsoft Docs[^]

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MatrixRatrix20-Dec-18 2:29

Re: c# listview Update problem

20-Dec-18 2:29

Hello,

I am new on C#, and I have a problem.

O make a form1 with listview,and i polulate this listview whit some Items.

Then I make another form2 with a button, just for count the items on Listview.

I create one function on Form1:

public void UpdatePart()
{

    MessageBox.Show(listView1.Items.Count.ToString());


}

In form2 I create a Button:

private void button1_Click(object sender, EventArgs e)
{
    Form1 a = new Form1();


    a.UpdatePart();
}

So, this count return always 0, but the listview on form1 is not empty, If I call
the same function but on the same form1, the code work and return the items numbers on listview.

What is rong ?

Thanks

Richard Deeming20-Dec-18 2:36

Re: c# listview Update problem

20-Dec-18 2:36

MatrixRatrix wrote:

private void button1_Click(object sender, EventArgs e)
{
    Form1 a = new Form1();
    a.UpdatePart();
}

Read that code again. You create a new, empty instance of Form1, and call the UpdatePart method on that instance. Since the new, empty instance doesn't have any items in the list, it will always display 0.

You need to call the method on the existing instance of Form1.

Transferring information between two forms, Part 1: Parent to Child[^]
Transferring information between two forms, Part 2: Child to Parent[^]
Transferring information between two forms, Part 3: Child to Child[^]

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

MatrixRatrix20-Dec-18 2:49

Re: c# listview Update problem

20-Dec-18 2:49

Thank you, I will check Smile | :)

BillWoodruff20-Dec-18 2:51

BillWoodruff

20-Dec-18 2:51

In addition to following Richard Deeming's excellent advice, see this recent answer to a similar problem: [^]

«Where is the Life we have lost in living? Where is the wisdom we have lost in knowledge? Where is the knowledge we have lost in information?» T. S. Elliot

KKSPANDICEO19-Dec-18 1:18

KKSPANDICEO

19-Dec-18 1:18

I HAVE BEEN CREATED THE INTERNET DOWNLOAD MANAGER.
I AM USING METHOD FOR FILEDOWNLOADASYN

HOW TO CREATE PAUSE,RESTART PROGRAM SIR?

Re: C#

OriginalGriff19-Dec-18 1:19