How to access multiple controls thread safe in Windows Forms

[poda]

Many examples explains thread safe access over a single control,like updating a text of a button or label etc.,How to change properties of multiple controls of a Form in thread safe manner.

private Thread CheckStatusThread = null;
public delegate void CheckStatusDelegate(int Count);
public CheckStatusDelegate CheckStatusHandler;

public Form1()
{
InitializeComponent();
CheckStatusThread = new Thread(new ThreadStart(CheckStatusThreadFunc));
CheckStatusHandler = new CheckStatusDelegate(CheckPowerStatus);
}
private void Form1_Load(object sender, EventArgs e)
{
CheckStatusThread.Start();
}
public void CheckStatusThreadFunc()
{
int Cnt = 1;
while (true)
{
this.Invoke(CheckStatusHandler,new object []{Cnt});//executed in Form1's own thread(?)
Cnt++;
Thread.Sleep(500);
}
}

public void CheckPowerStatus(int Count)
{
int Cnt=Count;

//Update 3 controls properties
StatusBarLabel1.Text = "Checking PowerStatus " + Cnt;
dataGridView1.Rows[2].Cells[4].Value = Cnt;
label1.Text = Convert.ToString("Cnt "+Cnt);
}

The CheckPowerStatus function change properties of 3 controls in Form1. Do I need to use 3 delegates to update each control on 3 different functions. Or the above code is thread safe?

[Mycroft Holmes]

All threading issues get referred to Luc - see his articles[^] here.

Never underestimate the power of human stupidity RAH

[Luc Pattyn]

you're not allowed to touch a Control from a random thread, so yes you need one or more Invoke calls. The proper way to handle simultaneous Control updates is by stuffing all the data you need in a little suitcase (i.e. a little class) and invoke once, let the delegate unpack the suitcase and do whatever needs to be done to the GUI. Assuming all GUI Controls got created on the main thread, all those Control.Invoke calls are equivalent anyhow, they all send the delegate to the main thread, no matter what they do to which Control. This[^] article of mine explains the basics, you may know most of it already. :)

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[Luc Pattyn]

Interesting link. :rose:

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[poda]

In article, you suggest to use Control and the property as generic parameter. But Control is the base class.The common property is only Text for all controls. But in case of specific properties of a control,how can use generic method. Suppose DataGridView.Rows[2].Cells[3].Value-how can use Control? Because Control.Rows does not exists. So if I need to update or access 3 controls 2 properties, then have to write 6 delegates and 6 functions to do the job?

[Luc Pattyn]

Actually I already answered that; here is one way:

// the anonymous form (C# consumer)
public void SetCount(int count) {
dataGridView1.Invoke(new MethodInvoker(delegate() {
StatusBarLabel1.Text = "Checking PowerStatus " + count;
dataGridView1.Rows[2].Cells[4].Value = count;
label1.Text = Convert.ToString("Cnt "+count);
}));
}

:)

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[realJSOP]

Required reading, if you ask me. :)

.45 ACP - because shooting twice is just silly
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[poda]

Thanks for your replies Luc Pattyn. Here you only use dataGridView1.Invoke, but update other controls also.Is that ok?

[poda]

Would you please kindly refer me some links.

[Luc Pattyn]

poda wrote:

Is that ok?

Yes. I told you before: all those Control.Invoke calls are equivalent anyhow, they all send the delegate to the main thread, no matter what they do to which Control. And you're welcome. :)

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