Flash drive write performance tester (C#)

using System;
using System.Drawing;
using System.Windows.Forms;
using System.Text;
using System.IO;
using System.Threading;
using System.Reflection;

[assembly: AssemblyTitle("Flash write performance tester 0.4")]
[assembly: AssemblyDescription("A small C# utility benchmarks the write performance in megabytes per second of a given flash drive")]
[assembly: AssemblyCompany("www.808.dk")]
[assembly: AssemblyProduct("FlashTester")]
[assembly: AssemblyCopyright("Creative Commons Attribution (CC BY 3.0) http://creativecommons.org/licenses/by/3.0/ Reference source http://www.808.dk/?code-csharp-driveperformance")]
[assembly: AssemblyVersion("0.4.0.0")]
[assembly: CLSCompliant(true)]

public class FlashPerformanceForm : Form
{
  Label driveLabel = new Label();
  Label fileSizeLabel = new Label();
  Label loopsLabel = new Label();
  Button benchmarkButton = new Button();
  ComboBox driveLetter = new ComboBox();
  ComboBox fileSize = new ComboBox();
  ComboBox loops = new ComboBox();
  TextBox resultArea = new TextBox();
  string testDriveLetter;
  int testFileSize;
  int testIterations;

  public FlashPerformanceForm()
  {
    this.Text = "Flash write performance tester 0.4";
    this.Size = new Size(400,350);
    driveLabel.Location = new Point(5, 8);
    driveLabel.Text = "Device drive letter";
    driveLabel.Size = new Size (95, 20);
    driveLetter.Location = new Point(103, 5);
    driveLetter.Size = new Size(33, 15);
    driveLetter.Items.AddRange(GetRemovableDriveLetters());
    if (GetRemovableDriveLetters().Length > 0)
    {
      driveLetter.SelectedIndex = 0;
    }
    fileSizeLabel.Location = new Point(141, 8);
    fileSizeLabel.Text = "File size";
    fileSizeLabel.Size = new Size(50, 20);
    fileSize.Location = new Point(193, 5);
    fileSize.Size = new Size(49, 15);
    fileSize.Items.AddRange(new object[]
      {"100",
       "200",
       "400",
       "800",
       "1000",
       "2000"});
    fileSize.SelectedIndex = 1;
    loopsLabel.Location = new Point(248, 8);
    loopsLabel.Text = "Loops";
    loopsLabel.Size = new Size(36, 20);
    loops.Location = new Point(284, 5);
    loops.Size = new Size(37, 15);
    loops.Items.AddRange(new object[]
      {"1",
       "2",
       "3",
       "4",
       "5",
       "10",
       "20",
       "40"});
    loops.SelectedIndex = 4;
    benchmarkButton.Location = new Point(329, 5);
    benchmarkButton.Size = new Size(50, 20);
    benchmarkButton.Text = "Start";
    resultArea.Location = new Point(5, 30);
    resultArea.Size = new Size(375,278);
    resultArea.ReadOnly = true;
    resultArea.Multiline = true;
    resultArea.ScrollBars = ScrollBars.Vertical;
    resultArea.WordWrap = false;
    resultArea.Font = new Font("Courier New", 8);
    this.Controls.Add(driveLabel);
    this.Controls.Add(driveLetter);
    this.Controls.Add(fileSizeLabel);
    this.Controls.Add(fileSize);
    this.Controls.Add(loopsLabel);
    this.Controls.Add(loops);
    this.Controls.Add(benchmarkButton);
    this.Controls.Add(resultArea);
    benchmarkButton.Click += new EventHandler(benchmarkButton_Click);
  }
  private void benchmarkButton_Click(object sender, EventArgs e)
  {
    testDriveLetter = driveLetter.Text + ":";
    testFileSize = Convert.ToInt32(fileSize.Text) * 1000000;
    testIterations = Convert.ToInt32(loops.Text);
    Thread testThread = new Thread(new ThreadStart(TestPerf));
    testThread.Start();
  }

  private void TestPerf()
  {
    try
    {
      int appendIterations = testFileSize / 100000;
      resultArea.AppendText(
        "Running a " + testFileSize/1000000 + "MB file write on drive "
        + testDriveLetter + " " + testIterations + " times...\r\n");
      double totalPerf = 0;
      DateTime startTime;
      DateTime stopTime;
      string randomText = RandomString(100000);
      for(int j=1; j<=testIterations; j++)
      {
        Application.DoEvents();
        if (File.Exists(System.Environment.CurrentDirectory + "\\" +
          j + "test.tmp"))
        {
          File.Delete(System.Environment.CurrentDirectory + "\\" +
            j + "test.tmp");
        }
        StreamWriter sWriter = new StreamWriter(
          System.Environment.CurrentDirectory + "\\" + j +
          "test.tmp", true);
        for(int i=1; i<=appendIterations; i++)
        {
          sWriter.Write(randomText);
        }
        sWriter.Close();
        startTime = DateTime.Now;
        File.Copy(System.Environment.CurrentDirectory + "\\" + j +
          "test.tmp", testDriveLetter + "\\" + j + "test.tmp");
        stopTime = DateTime.Now;
        File.Delete(System.Environment.CurrentDirectory + "\\" + j +
          "test.tmp");
        File.Delete(testDriveLetter + "\\" + j + "test.tmp");
        TimeSpan interval = stopTime - startTime;
        resultArea.AppendText("Iteration " + j + ":   " +
          Math.Round((testFileSize/1000)/interval.TotalMilliseconds, 2) +
          " MB/sec\r\n");
        resultArea.Invalidate();
        totalPerf += (testFileSize/1000)/interval.TotalMilliseconds;
      }
      resultArea.AppendText("------------------------------\r\n");
      resultArea.AppendText("Average:       " +
        Math.Round(totalPerf/testIterations, 2) + " MB/sec\r\n");
      resultArea.AppendText("------------------------------\r\n");
      resultArea.Invalidate();
    }
    catch (Exception e)
    {
      resultArea.AppendText("An error occured: " + e.Message + "\r\n");
    }
  }

  private string RandomString(int size)
  {
    StringBuilder builder = new StringBuilder();
    Random random = new Random();
    char ch;
    for (int i = 0; i < size; i++)
    {
      ch = Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65)));                
      builder.Append(ch);
    }
    return builder.ToString();
  }

  private string[] GetRemovableDriveLetters()
  {
    System.Collections.ArrayList RemovableDriveLetters = new System.Collections.ArrayList();
    DriveInfo[] allDrives = DriveInfo.GetDrives();
    foreach (DriveInfo d in allDrives)
    {
      if (d.DriveType == DriveType.Removable)
      {
        RemovableDriveLetters.Add(d.Name.Substring(0, 1));
      }
    }
    return RemovableDriveLetters.ToArray(typeof(string)) as string[];
  }

  static void Main()
  {
    Application.Run(new FlashPerformanceForm());
  }
}

C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\csc.exe /target:winexe /out:FlashTester.exe FlashTester.cs