Picture Converter

private void btnConvert_Click(object sender, EventArgs e)
        {
            if (txtInput.Text != "")
            {
                // Find files and put them into oldFiles
                DirSearch(txtInput.Text);

                // Setup the progress bar
                tsProgressBar.Maximum = oldFiles.Count;
                tsProgressBar.Step = 1;
                tsProgressBar.Visible = true;

                // Do the converting and update progress bar
                for (int i = 0; i < oldFiles.Count; i++)
                {
                    SaveBmpAsPNG(oldFiles[i], newFiles[i]);
                    tsProgressBar.PerformStep();
                    tsStatusLabel.Text = "Converting " + oldFiles[i];
                }
            }
            // Clean up
            oldFiles.Clear();
            newFiles.Clear();
            tsStatusLabel.Text = "";
            tsProgressBar.Value = 0;
            tsProgressBar.Visible = false;
        }

        // Function to convert bitmaps to png files
        private void SaveBmpAsPNG(string oldFile, string newFile)
        {
            Bitmap bmp1 = new Bitmap(oldFile);
            bmp1.Save(@newFile, System.Drawing.Imaging.ImageFormat.Png);
        }

        // Folder recursion
        void DirSearch(string sDir)
        {
            // Create the folder structure in the output folder
            foreach (string dirPath in Directory.GetDirectories(txtInput.Text, "*",
                SearchOption.AllDirectories))
            {
                // Variable to hold the new folder structure
                string newFolder = dirPath.Replace(sDir, txtOutput.Text);
                // Check if the folder exists
                if (!Directory.Exists(newFolder))
                {
                    // Create the new folder
                    Directory.CreateDirectory(newFolder);
                }
                else
                {
                    //MessageBox.Show("Folder already exists:\n" + newFolder, "Folder Exists!");
                }
            }
            foreach (string f in Directory.GetFiles(sDir, "*.bmp"))
            {
                // Process files in directory
                string newName = f.Substring(0, f.Length - 3) + "png";
                newName = newName.Substring(txtInput.TextLength, newName.Length - txtInput.TextLength);
                newName = txtOutput.Text + newName;
                oldFiles.Add(f);
                newFiles.Add(newName);
                //MessageBox.Show(f + "\n" + newName);
            }

            foreach (string d in Directory.GetDirectories(sDir))
            {
                DirSearch(d);
            }
        }