How to showdialog a Please Wait window when fetching data

Question

4.00/5 (1 vote)

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Hi I using below code to fetching data and i showing a window with a short message:"please wait..."

in main window:

C#

private static frmLoading _loading = null;

        private void StartLoading(bool value)
        {
            if (value == true)
            {
                _loading = new frmLoading();
                _loading.Show(this);
            }
            else
            {
                CloseLoading();
            }
        }

        public static void CloseLoading()
        {
            if (_loading != null)
            {
                _loading.CloseLoading();
            }
        }

in button click event (main window):

XML

Thread t = new Thread(new ThreadStart(delegate
            {
                this.Invoke(new Action<bool>(StartLoading), true);

                this.Invoke((MethodInvoker)delegate { GetData(); });

                this.Invoke(new Action<bool>(StartLoading), false);

            }));
            t.Start();

in frmLoading:

C#

public void CloseLoading()
        {
            Invoke((MethodInvoker)delegate
            {
                this.Close();
            });
        }

but my problem is: i click on button cod is working and frmLoading is show but when i click on main form, application hanging and hang is continue until data fetching is complete.
and when i using ShowDialog() method (in this line: _loading.Show(this)) No Data Fetching!
what i do?!

another question, is this solution efficient?

thanks

Posted 29-Aug-14 3:27am

maysamfth

Updated 29-Aug-14 3:39am

v3

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BotCar · Accepted Answer · 2014-08-29T03:58:00

When you use this.Invoke to call GetData, you are forcing GetData to execute on the UI thread. This means that any interaction with the main window or the dialog window will have to wait for GetData to finish executing.

Try changing your button click event to:

C#

Thread t = new Thread(new ThreadStart(delegate
{
   this.Invoke(new Action<bool>(StartLoading), true);
 
   GetData();
 
   this.Invoke(new Action<bool>(StartLoading), false);
 
}));
t.Start();

ShowDialog is a blocking call, which means it will show the window and wait for the user to close the window before continuing with the next statement. This means that GetData will only be called after you close the window.

Edit:
To prevent the user from messing with the main window, you could also kick off GetData on a background thread just before showing frmLoading as a dialog. This will block the UI thread while frmLoading is open, so you will have to programmatically close it just before updating your datagrid.

C#

void button_Click(object sender, EventArgs e)
{
   new Action(GetData).BeginInvoke(null, null);
   this.Invoke(new Action<bool>(StartLoading), true);
}

void GetData()
{
   // Fetch your data from database or wherever...

   // Do any processing you want to do on your data

   this.Invoke(new Action<bool>(StartLoading), false);
   this.Invoke(new Action(FillDataGrid));
}

void FillDataGrid()
{
   // Fill your datagrid
}

Links you might find useful:
http://stackoverflow.com/questions/1130208/how-to-disable-the-parent-form-when-a-child-form-is-active[^]
http://support.microsoft.com/kb/318607[^]

Ravi Bhavnani · Accepted Answer · 2014-08-29T04:59:00

Solution 2

Use a BackgroundWorker to fetch your data. This will allow your UI to be notified of the fetch progress and completion, and will also allow the fetch to be cancelled by the user.

See this[^] article as an example.

/ravi

Posted 29-Aug-14 4:59am

Ravi Bhavnani