Re: Using Thread is not successful - C# Discussion Boards

27-Jul-12 16:08

Hi Friends,

I am trying to create a new thread to make the picturebox is visible (to show Loading icon) when the ConvertFiles method is running, but it is not successful (Please see below codes)

Do you know what's wrong ?

private void ShowLoadingIcon()
        {
            if (InvokeRequired)
            {
               this.Invoke (new MethodInvoker( ShowLoadingIcon));

            }
            else
            {
                pixLoadingIcon.Visible = true;
            }
        }
private void btnConvert_Click(object sender, EventArgs e)
        {
            
                Thread thLoading = new Thread(ShowLoadingIcon);
                thLoading.Start();
                // This method will take a few minutes
                ConvertFiles(sourceFile, destinationFile);
        }

Thanks and regards,

Wes Aday27-Jul-12 16:32

Wes Aday

27-Jul-12 16:32

taibc wrote:
but it is not successful

What does this mean? The thread does not start? The thread starts but does not do anything? The code runs and your cat died? "it's not successful" does not tell us anything about what your problem is. Did you run it through a debugger? What did you discover?

Why is common sense not common?
Never argue with an idiot. They will drag you down to their level where they are an expert.
Sometimes it takes a lot of work to be lazy
Please stand in front of my pistol, smile and wait for the flash - JSOP 2012

Trak4Net27-Jul-12 17:46

Trak4Net

27-Jul-12 17:46

I think you are doing this backwards. The invoke back to the UI thread will be blocked until your long processing task is finished.

You should actually be trying to do something like this

string sourceFile, destinationFile;

       private void ShowLoadingIcon()
       {
           if (InvokeRequired)
           {
               this.Invoke(new MethodInvoker(ShowLoadingIcon));

           }
           else
           {
               pixLoadingIcon.Visible = true;
           }
       }



       private void btnConvert_Click(object sender, EventArgs e)
       {
           ShowLoadingIcon();

           //start thread to process long running task
           System.Threading.Thread t = new System.Threading.Thread(() =>
           {
               ConvertFiles(sourceFile, destinationFile);
           });

           t.Start();

       }


       private void ConvertFiles(string src, string dest)
       {
           //long running task to convert files
       }

taibc27-Jul-12 20:21

27-Jul-12 20:21

Great ! It is successful now.

Thanks Trak4Net very much. Thumbs Up | :thumbsup:

taibc6-Aug-12 18:21

6-Aug-12 18:21

Hi Trak4Net,

When running the new thread, I got the bellow error:

"{Text = '((System.Windows.Forms.TextBox)(txtLopDiaChi)).Text' threw an exception of type 'Microsoft.VisualStudio.Debugger.Runtime.CrossThreadMessagingException'} System.Windows.Forms.TextBox
"

Do you know how to fix it ?

Thanks and regards,

Trak4Net13-Aug-12 19:04

Trak4Net

13-Aug-12 19:04

You should read up about making thread-safe calls to controls here is one link http://msdn.microsoft.com/en-us/library/ms171728.aspx[^]

Anytime you access a control from a thread other than the thread the control was created on you will need to use Invoke or BeginInvoke to modify. Usually if there are several common controls I create a method that accepts a control as a parameter as well as the text to set and inside that method it checks if invoke is required.

Here is an example of something you could do. You don't show enough code to know exactly what you are trying but this can be modified to work with different controls etc.

Hope this is helpful.

/// <summary>
/// delegate to invoke when invoke required
/// </summary>
private delegate void ChangeTextDel(System.Windows.Forms.TextBox obj, string newtext);

/// <summary>
/// Changes the text.
/// </summary>
/// <param name="obj">The obj.</param>
/// <param name="newtext">The newtext.</param>
private void ChangeText(System.Windows.Forms.TextBox obj, string newtext)
{
    if (obj.InvokeRequired)
    {
        obj.Invoke(new ChangeTextDel(ChangeText), new object[] { obj, newtext });
    }
    else
    {
        obj.Text = newtext;
    }
}

//from thread
ChangeText(txtLopDiaChi, "my new text value");

taibc13-Aug-12 20:44

how to set label text here?

13-Aug-12 20:44

Thank you.

I resolved this error earlier.

Kind regards,

Tai

Jassim Rahma27-Jul-12 7:36

Jassim Rahma

27-Jul-12 7:36

Hi,

I am searching for MDI child using this code and activating it when exists.

I want to know how can I set label text before the search_form.Activate() line? I tried search_form.lblFindWhat.Text = "something" but it was not recognized although i set the lblFindWhat Modifier to Public.

here is the code:

foreach (Form search_form in this.MdiChildren)
{
    if ((string)search_form.Tag == "BROWSE_PATIENTS")
    {
        search_form.lblFindWhat.Text = "something";
        search_form.Activate();
        is_form_exists = true;
        break;
    }
}

Ravi Bhavnani27-Jul-12 8:09

Ravi Bhavnani

27-Jul-12 8:09

What do you mean by "but it was not recognized"? Did the code compile?

/ravi

My new year resolution: 2048 x 1536
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Jassim Rahma27-Jul-12 9:25

Jassim Rahma

27-Jul-12 9:25

I mean getting this error:

Error   9   'System.Windows.Forms.Form' does not contain a definition for 'lblFindWhat' and no extension method 'lblFindWhat' accepting a first argument of type 'System.Windows.Forms.Form' could be found (are you missing a using directive or an assembly reference?)   C:\Users\Jassim\Documents\Visual Studio 2010\Projects\Cure\Cure\main_form.cs    1682    37  Cure

Ravi Bhavnani27-Jul-12 9:40

Ravi Bhavnani

27-Jul-12 9:40

The compiler is correct. A Form doesn't define a lblFindWhat member. You need to cast search_form to the specialized type of the form you're using before accessing its lblFindWhat member.

/ravi

My new year resolution: 2048 x 1536
Home | Articles | My .NET bits | Freeware
ravib(at)ravib(dot)com

OriginalGriff27-Jul-12 9:16

OriginalGriff

27-Jul-12 9:16

Please, don't set controls to public - it fixes the design of the form, because you can't change the label out without it affecting (and possibly breaking) outside objects.

Instead, create a public property which allows access, and set the label text yourself within the property. That way, you can replace the label with a more suitable control at some future date, and nothing gets changed outside.
In your search form:

public string Prompt
   {
   get { return myLabel.Text; }
   set { myLable.Text = value; }
   }

In your external class:

search_form.Prompt = "something";

The next problem is that a Form does not contain your controls. You have to cast it to an instance of your search form before the compiler can know what it contains:

foreach (Form form in this.MdiChildren)
{
    MySearchForm search_form = form as MySearchForm;
    if (search_form != null && (string)search_form.Tag == &quot;BROWSE_PATIENTS&quot;)
    {
        search_form.Prompt = "something";
        search_form.Activate();
        is_form_exists = true;
        break;
    }
}

Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water

Ravi Bhavnani27-Jul-12 9:41

Ravi Bhavnani

27-Jul-12 9:41

Ugh. I should've just pointed the OP to your post. Smile | :)

/ravi

My new year resolution: 2048 x 1536
Home | Articles | My .NET bits | Freeware
ravib(at)ravib(dot)com

Track two types of values within one variable

OriginalGriff27-Jul-12 9:47

OriginalGriff

27-Jul-12 9:47

I do it all the time...

Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water

hpjchobbes27-Jul-12 4:55

hpjchobbes

27-Jul-12 4:55

I'm still new, so I don't know if this is the best way to do what I am needing, and would like some feedback/advice.

I have a class that contains a double value. This double could represent a dollar value or it could represent a percentage value. Only one or the other, it will never have both. At runtime, I will need to be able to tell what type of value this is. Here is what I came up with, which appears to work, but if there is a better way, I would prefer that.

public class Rate
{
     public double Value; // Holds either the dollar or percentage value
}
public class RateDollar : Rate {}
public class RatePercentage : Rate {}

public class TransactionLine
{
   // There's more stuff here, but it's not relevant to show
   public Rate Amount;
}


// Set the rate amount to be a dollar 
myTransactionLine.Amount = new RateDollar();

// I can check the type if needed
if(myTransactionLine.Amount.GetType() == typeof(RateDollar)) // We have a dollar value
if(myTransactionLine.Amount.GetType() == typeof(RatePercent)) // We have a percentage value

For some reason, this seems like it is a clunky workaround. It also seems like it's possible for someone to create the value that is neither a RateDollar or RatePercent, and just as a plain Rate. Is there some way to prevent this, or is there a better way to accomplish what I am trying to do?

SledgeHammer0127-Jul-12 6:28

SledgeHammer01

27-Jul-12 6:28

It doesn't make much sense to have a Rate class if all it does is contain a double. Is there more to it then that? Is the Rate used elsewhere? I'm gonna go out on a limb and say that TransactionLine should just have a double Rate property and a RateType enum property that says whether its a % or $ amount.

hpjchobbes27-Jul-12 7:04

hpjchobbes

27-Jul-12 7:04

Thanks for the response! The enum seems like it would be a simpler way to handle this. Since the Rate may be used in multiple different classes, I think I should go with an enum in the Rate class.

public enum ENRateType { Dollar, Percent }

public class Rate
{
    public ENRateType RateType;
    public double Rate;
}

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27-Jul-12 6:38

N_tro_P

27-Jul-12 6:38

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hpjchobbes27-Jul-12 7:18

hpjchobbes

27-Jul-12 7:18

Thanks for responding!

I haven't really gotten to learning a lot about interfaces (or abstract classes), but I am thinking that will be the next topic I tackle.

The reason for this setup is because I am interacting with another software, and that software has one value that represents either a dollar value or a percentage. For example, this is how it would show a transaction:

Widget          $12.00
Shipping        $3.95
Subtotal        $15.95
Tax             8.875%
Total           $30.11

When I get this information from the program, they have a rate class that contains three members, an enum for the price type (dollar or percent), a double for the Dollar value, and a double for the Percent value. Because the line can only be a dollar or value and not both, one of the doubles will always be null.

I get the feeling (but I may be wrong) that they way they did their setup isn't the best. I will probably implement a Rate class that contains an enum and a double, which should work, but if there is a 'better' way to do this, I would prefer to learn about that type of implementation.

BillWoodruff29-Jul-12 18:35

BillWoodruff

29-Jul-12 18:35

To me this information indicates you are "free" to change the Rate class in the program you get the information from: is that correct ?

The use of the phrases "They have," and "they did," and, "I am interacting with another software," is what gives me the idea you may not have freedom to change the Rate class.

thanks, Bill

"Everything we call real is made of things that cannot be regarded as real." Niels Bohr

SledgeHammer0127-Jul-12 11:40

SledgeHammer01

27-Jul-12 11:40

Definitely would not use an interface here. Whats the point? Not everything needs to be an interface. Having 3 classes (or interfaces or whatever) just to hold a double is over engineering at its finest Smile | :)

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27-Jul-12 12:22

N_tro_P

27-Jul-12 12:22

Message Removed