Thumbnail image in c#

private void btnBrowse_Click(object sender, EventArgs e)
       {

           lstImagename.Items.Clear();

           if(dlgFolder.ShowDialog() == DialogResult.OK)
           {
               var filePaths = Directory.GetFiles(strFldrpath, "*.*", SearchOption.AllDirectories)
           .Where(s => s.EndsWith(".gif") || s.EndsWith(".jpg") || s.EndsWith(".bmp"));

               //string[] filePaths = Directory.GetFiles(strFldrpath, strExt);
               int length = filePaths.Count();
               int i = 0;
               while (length > i)
               {

                   lstImagename.Items.Add(new FileInfo(filePaths.ElementAt(i).ToString()).Name);
                   i++;
               }
               if (lstImagename.Items.Count == 0)
               {
                   MessageBox.Show("Image(s) not available", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Information);
                   DialogResult resYesNo;
                  resYesNo = MessageBox.Show("Do you want to continue ", "Warning", MessageBoxButtons.YesNo, MessageBoxIcon.Information);
                  if (resYesNo == DialogResult.Yes)
                  {
                      btnBrowse_Click(sender, e);
                  }
                  else
                  {
                  //Nothing in here
                      txtFldrpath.Text = "";

                  }
               }
               txtFldrpath.Text = strFldrpath;
               }
            }

      private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
       {
           strImgName = txtFldrpath.Text + "\\" + lstImagename.SelectedItem;
           pbxImg.Image = Image.FromFile(strImgName);
       }

      private void buttin_Click(object sender, EventArgs e)
      {
          if ((pbxImg.Width <= 322) & (pbxImg.Height <= 290))
          {
              pbxImg.Width = pbxImg.Width + 10;
              pbxImg.Height = pbxImg.Height + 10;
          }
      }

      private void buttout_Click(object sender, EventArgs e)
      {
          if ((pbxImg.Width >= 1) & (pbxImg.Height >= 1))
          {
              pbxImg.Width = pbxImg.Width - 10;
              pbxImg.Height = pbxImg.Height - 10;
          }
      }
       }