How to access GUI from another thread? - C# Discussion Boards

11-Feb-21 7:10

I tried to simulate a process in which by pressing a button, some calculations take place (I used a tutorial). Now, I want to test and learn how I can manipulate GUI from an another thread. I decided to change button1 text. I added its code to DoWork section. As I expected, it throws cross-thread exception. Please write me a code and use Invoke and Delegate to see how I can access GUI. I want to learn from your code. Thanks.

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            button1.Text = "processing";
            int sum = 0;
            for (int i = 0; i <= 100; i++)
            {
                Thread.Sleep(100);
                sum = sum + i;
                backgroundWorker1.ReportProgress(i);
                if (backgroundWorker1.CancellationPending)
                {
                    e.Cancel = true;
                    backgroundWorker1.ReportProgress(0);
                    return;
                }
            }
            e.Result = sum;
        }


        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            progressBar1.Value = e.ProgressPercentage;
            label1.Text = e.ProgressPercentage + "%";

        }

        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled)
            {
                label1.Text = "Process canceled";
            }
            else if (e.Error != null)
            {
                label1.Text = e.Error.Message;
            }
            else
            {
                label1.Text = "Result: " + e.Result.ToString();
            }

        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (!backgroundWorker1.IsBusy)
            {
                backgroundWorker1.RunWorkerAsync();
            }
            else
            {
                MessageBox.Show("Busy processing!. Please wait...");
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (backgroundWorker1.IsBusy)
            {
                backgroundWorker1.CancelAsync();
            }
            else
            {
                label1.Text = "No operation is running to cancel.";
            }
        }
    }

modified 11-Feb-21 14:05pm.

Gerry Schmitz11-Feb-21 7:39

Gerry Schmitz

11-Feb-21 7:39

UWP, WPF or Windows Forms?

Seems optimistic to "report progress" when "cancelling" ... that's RunWorkerCompleted territory.

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

Alex Dunlop11-Feb-21 7:40

11-Feb-21 7:40

it's Win Form.

Alex Dunlop11-Feb-21 8:07

11-Feb-21 8:07

Consider that I have to keep order of my operations, so

button1.Text = "processing"

needs to be in DoWork section.

Dave Kreskowiak11-Feb-21 13:17

Dave Kreskowiak

11-Feb-21 13:17

No, you don't.

UI stuff like that should happen outside the BackgroundWorker, like right before you start it on its way.

Asking questions is a skill
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Google: C# How to debug code
Seriously, go read these articles.

Dave Kreskowiak

Gerry Schmitz11-Feb-21 9:03

Gerry Schmitz

11-Feb-21 9:03

1) Add reference to WindowsBase.dll

2) Add: using System.Windows.Threading;

3) Add delegate declaration OUTSIDE of method:

delegate void ProgressDelegate( int pct );

4) Replace (in this case):

backgroundWorker1.ReportProgress(i);

with:

ProgressDelegate progressDelegate = delegate ( int pct ) { this.progressBar1.Value = pct; };

System.Windows.Threading.Dispatcher.CurrentDispatcher.BeginInvoke(
   DispatcherPriority.Normal, progressDelegate, percentComplete );

Then it's just a matter of tailoring for various UI controls.

It was only in wine that he laid down no limit for himself, but he did not allow himself to be confused by it.
― Confucian Analects: Rules of Confucius about his food

Ralf Meier11-Feb-21 10:36

Ralf Meier

11-Feb-21 10:36

Isn't that the same question that you ask here :
Re: BackGroundWorker gives runtime error - C# Discussion Boards[^]

Did you give those links, I gave to you at that question, a try ?
If not - why not ?
If yes - where do you stuck ?

To Clarify :
Invoke means that you give an order to do something outside your Thread or Worker which originally happen inside the UI-Thread.

Luc Pattyn11-Feb-21 11:29

Luc Pattyn

11-Feb-21 11:29

That basically is the same question once more. The answer hasn't changed.

You are wasting your and our time by repeating your question and ignoring the answers you've got. Mad | :mad:

Luc Pattyn [My Articles]
If you can't find it on YouTube try TikTok...

Eddy Vluggen11-Feb-21 14:01

Eddy Vluggen

11-Feb-21 14:01

Luc Pattyn wrote:

No, Master Luke.

(Ghhh.. I am your father, ghhhh)

Luc Pattyn wrote:
You are wasting your and our time

He has the right to do so; to be ignorant. There's always those looking for easy answers, unwilling to learn. This site is easy money for some. I learned a lot from you, mostly that I should be patient.

Want to tell him he's wasting money? This is voluntary, remember? If he insist on failing, I'd for one gladly help.

Bastard Programmer from Hell Suspicious | :suss:

"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.

Alex Dunlop11-Feb-21 18:18

11-Feb-21 18:18

I'm not wasting your time. I couldn't find out how to use the procedure in my own situation.
For example, based on the explanations in Towards Cleaner Code II, a C# GUI Invoke/Async Helper [^] I wrote the following code:

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
    //button1.Text = "processing";
    if (button1.InvokeRequired)
    {
        button1.Invoke(delegate { updatetext("Processing"); });
    }
    else
    {
        updatetext("Processing");
    }

    int sum = 0;
    for (int i = 0; i <= 100; i++)
    {
        Thread.Sleep(100);
        sum = sum + i;
        backgroundWorker1.ReportProgress(i);
        if (backgroundWorker1.CancellationPending)
        {
            e.Cancel = true;
            backgroundWorker1.ReportProgress(0);
            return;
        }
    }
    e.Result = sum;
}
private void updatetext(string txt)
{
    button1.Text = txt;
}

But,

button1.Invoke(delegate { updatetext("Processing"); });

says the method is not a delegate type and cannot be compiled.

modified 12-Feb-21 0:54am.

Alex Dunlop11-Feb-21 19:39

11-Feb-21 19:39

I found my own solution:

button1.Invoke((Action)delegate { updatetext("Processing"); });

button1.Invoke((MethodInvoker)delegate { updatetext("Processing"); });

Message Closed

11-Feb-21 14:18

Eddy Vluggen

11-Feb-21 14:18

Message Closed

modified 13-Feb-21 8:00am.

Alex Dunlop11-Feb-21 18:16

JsonConvert.DeserializeObject

11-Feb-21 18:16

I'm not stupid.

Member 1449252210-Feb-21 21:43

Member 14492522

10-Feb-21 21:43

Good morning I have a problem that is making me desperate. I want to deserelize a Json but the content is always null. I pass you my code, if you could give me a hand I would appreciate it very much.
Regards and thank you very much in advance.

CLASS

public class RootContactos
{

public string contacto { get; set; }
public string email { get; set; }
public string telefono { get; set; }
public string notas { get; set; }

}

CODE

contac = JsonConvert.DeserializeObject<rootcontactos>(strJson);

JSON

{"20150630140000#1":{"contacto":"PATRICIA","telefono":"976185823","email":"","notas":""},"20150630140001#1":{"contacto":"FAX","telefono":"976180364","email":"","notas":""}}

OriginalGriff10-Feb-21 22:05

OriginalGriff

10-Feb-21 22:05

Your JSON does not match the class, which is probably why you get a problem. If I run your JSON through a class creator (Convert JSON to C# Classes Online - Json2CSharp Toolkit[^]) then what I get is three classes:

// Root myDeserializedClass = JsonConvert.DeserializeObject<Root>(myJsonResponse); 
    public class _201506301400001    {
        public string contacto { get; set; } 
        public string telefono { get; set; } 
        public string email { get; set; } 
        public string notas { get; set; } 
    }

    public class _201506301400011    {
        public string contacto { get; set; } 
        public string telefono { get; set; } 
        public string email { get; set; } 
        public string notas { get; set; } 
    }

    public class Root    {
        [JsonProperty("20150630140000#1")]
        public _201506301400001 _201506301400001 { get; set; } 
        [JsonProperty("20150630140001#1")]
        public _201506301400011 _201506301400011 { get; set; } 
    }

Which is what I would expect from that: two different classes with identical content but different names!

I'd start by looking at the data source - I'd expect an array of JSON data containing two elements, not two individual items.

Member 1449252211-Feb-21 4:13

Member 14492522

11-Feb-21 4:13

Thank you very much for answering. The classes that he proposes to me, I cannot perform them because the "header" (_201506301400001) varies in each record of the database.
I have been testing and I have managed to do the deserilization in this way:

var result = JsonConvert.DeserializeObject <dynamic> (strJson);

But then I have not gotten the information from resutl.
Regards and thank you very much in advance.

James Curran11-Feb-21 23:58

James Curran

11-Feb-21 23:58

Deserialize it into a Dictionary.

    void Main()
    {
        var json =@"{""20150630140000#1"":{""contacto"":""PATRICIA"",""telefono"":""976185823"",""email"":"""",""notas"":""""},""20150630140001#1"":{""contacto"":""FAX"",""telefono"":""976180364"",""email"":"""",""notas"":""""}}";

<pre>
    var contacDict  = JsonConvert.DeserializeObject<IDictionary<string,RootContactos>>(json);
    contacDict.Values.First().Dump();
    contacDict["20150630140001#1"].Dump();
}

public class RootContactos
{
    public string contacto { get; set; }
    public string email { get; set; }
    public string telefono { get; set; }
    public string notas { get; set; }
}</pre>

Truth,

James