延迟主线程，让新线程在加载之前工作

Question

I have win form application which load some data and fill a gridview using threads. In here the task of filling the grid take little while and therefore, at the moment it is using a separate thread to data fill task. So currently what happens is windows form initially load with the some information with the grid and after that it will filling the data to the grid while the user have responsive UI to play with.

In form load

DataBind();
var newThread = new Thread(new ThreadStart(FillGrid));
newThread.Start();

This FillGrid() method will each row and all the columns and depending on the value it will change the cell color and will add some data. What I am trying to achieve is rather than load the form with empty data, I would like to fill like half of the grid and continue filling the rest of grid after form loaded. I tried like using Thread.Sleep() after calling the newThread.Start() but didn't do what I expected.

Any help on achieving this!!!

And to access the gridview safely I refer to this article about Updating Your Form from Another Thread without Creating Delegates for Every Type of Update

Thanks

Answer 1

As already stated use BackgroundWorker.ReportProgress. But you will need to not continue to update the object you send back half way (see second link).

With that said look at what is causing the grid to fill slowly. Sending back 1/2 the data is only going to help a bit. How much time are you really going to save just loading 1/2 the data? Now you have two UI refreshes so the total time is longer.

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Answer 2

Use an AutoResetEvent - have the main thread wait and when you have half filled the grid; signal the main thread to procede..

http://msdn.microsoft.com/en-us/library/system.threading.autoresetevent.aspx

Answer 3

You should fill your grid while reading the data. Read the data in the secondary thread, then notify the UI thread when there's a chunk of data ready to be populated in the grid. You'll need to do a little thread juggling, because the UI needs to be updated from the main thread, but it shouldn't be too hard.

You can also try to use a BackgroundWorker , and update the grid in its ProgressChanged event.

Answer 4

In the background thread, do not touch the grid. Instead, use it only too fill your data somewhere, to some collection NOT BOUND to the grid.

Create Timer and in it's event PULL data from the collection that is filled in the background thread to the GUI.

That way, you won't have to worry about Invoke and all kinds of problems that you get into when talking to GUI from non-gui threads.

Answer 5

Here is a really simple example using a background worker. I hope it points you in the right direction.

Please notice how I used the the Me.Invoke() method to update the UI. This is required because all UI elements must be updated from the thread that created them.

Public Class Form1
    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        BackgroundWorker1.RunWorkerAsync()
    End Sub

    Private Sub BackgroundWorker1_DoWork(sender As System.Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Dim r As New Random()
        For index As Integer = 0 To 100
            Me.Invoke(Sub()
                          ListBox1.Items.Add(Guid.NewGuid().ToString())
                      End Sub)
            Threading.Thread.Sleep(r.Next(50, 300))
        Next
    End Sub

    Private Sub BackgroundWorker1_RunWorkerCompleted(sender As System.Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
        Me.Invoke(Sub()
                      MsgBox("Task Complete", MsgBoxStyle.OkOnly, "Task Complete")
                  End Sub)
    End Sub
End Class