FlowLayoutPanel Scroll to Bottom doesn't work properly

Question

I am currently working on a FlowLayoutPanel and I find that the ScrollControlIntoView may not always work correctly.
It seems that when I add about 1,000 PictureBoxes into the FlowLayoutPanel, I use the ScrollControlIntoView to move to the last PictureBox, It fails to do so. But, if I use the vertical scrollbar context menu "Bottom", it works.
So, how can I use the scrollbar context menu "Bottom" programmatically?
Or, there is other method that I can programmatically to move to the last controls inside the FlowLayoutPanel.

Answer 1

Hi @kwok kan ho , Welcome to Q&A.

Scrolling the container to the bottom may not always work as expected if the container has many controls and not enough space to display them all at once.

In this case, the scroll position may not be updated properly, or the container may not be able to scroll far enough to bring the last control into view.

In this situation, you may need to consider using a different container, such as a List View or a DataGrid View, which are better suited for displaying large numbers of items.

If you want to scroll to the bottom of the container, you can use the property of the container and set it to the maximum value.

this is my code:

private void Form1_Load(object sender, EventArgs e)  
{  
    for (int i = 0; i < 1000; i++)  
    {  
        PictureBox a = new PictureBox();  
        a.Image = pictureBox1.Image;  
        flowLayoutPanel1.Controls.Add(a);  
    }  
    flowLayoutPanel1.AutoScroll = true;  
    flowLayoutPanel1.VerticalScroll.Value = flowLayoutPanel1.VerticalScroll.Maximum;  
}  

Best Regards,
Jiale

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Answer 2

Hi Jiale,
Thank you for your reply and it works.
As you mentioned in your reply, it is better to use ListView or DataGrid. I have tried the ListView before I use the FlowLayoutPanel, but I found that the images displayed in ListView is not good enough. Because I am try to display the shellFile.Thumbnail.ExtraLargeBitmap of some jpg images. So, is there a way that I can display good quality of image using ListView of DataGridView?

The following is my code .

private void LoadThunbnailFromPhotoList(DataTable oTblPhotoList, string filterDate = "")  
{  
  int prevWidth = flpPhotoViewer.Width;  
  int prevHeight = flpPhotoViewer.Height;  

  Cursor = Cursors.WaitCursor;  
  txtMsg.AppendText("Photo Loading......", 1, true);  

  flpPhotoViewer.SuspendLayout();  

  if (flpPhotoViewer.Controls.Count > 0 )  
    flpPhotoViewer.Controls.Clear();  

  if (oTblPhotoList != null && oTblPhotoList.Rows.Count > 0)  
  {  
    List<PictureBox> picBoxes = new List<PictureBox>();  
    foreach(DataRow oRow in oTblPhotoList.Rows)  
    {  
      string imageFile = oRow["Filename"].ToString().Trim();  
      string shootingDate = oRow["ShootingDate"].ToString().Trim();  
      if (imageFile != "" && File.Exists(imageFile)  
       && (filterDate == "" || shootingDate.Equals(filterDate)))  
      {  
        PictureBox pictureBox = new PictureBox();  
        pictureBox.Name = "PicBox_" + i.ToString("0000#");  
        pictureBox.Tag = imageFile;  
        pictureBox.SizeMode = PictureBoxSizeMode.Zoom;  
        pictureBox.BackColor = gPicBoxBackColor;  
        pictureBox.BorderStyle = BorderStyle.FixedSingle;  

        toolTip1.SetToolTip(pictureBox, pictureBox.Name + "\r\n" + imageFile);  

        pictureBox.Width = picBoxWidth;  
        pictureBox.Height = picBoxHeight;  

        ShellFile shellFile = ShellFile.FromFilePath(imageFile);  
        pictureBox.Image = shellFile.Thumbnail.ExtraLargeBitmap;  
        shellFile.Dispose();  

        pictureBox.GotFocus += Control_GotFocus;  
        pictureBox.LostFocus += Control_LostFocus;  
        pictureBox.MouseClick += Control_MouseClick;  
        pictureBox.MouseDoubleClick += Control_MouseDoubleClick;  

        picBoxes.Add(pictureBox);  
      }  
    }  
    flpPhotoViewer.Controls.AddRange(picBoxes.ToArray());  
    picBoxes.Clear();  
    picBoxes = null;  
  }  
  // To make the first control visible   
  // and move to the top of flpPhotoView  
  flpPhotoViewer.VerticalScroll.Value = flpPhotoViewer.VerticalScroll.Minimum;  
  flpPhotoViewer.ResumeLayout();  

  txtMsg.AppendText("Photo Loading Completed......", 1, true);  
  Cursor = Cursors.Default;  
}  

Best Regards,
KK