[VB.NET]Creating a Basic Captcha String

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This was something I pulled from a test program I was messing with. I was writing an application to send some information to a remote database and to prevent "flooding" I could write in a captcha. Granted I would never include this because of how simple it is, it was rather easy.

First off our function to create the random string of letters.

  Private Function generateCaptchaString()
  Dim rand As New Random
  Dim currentLetter As String
  Dim captchaString As String = ""
  For i = 0 To 6
  currentLetter = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
  captchaString &= currentLetter
  Next

  Return captchaString
  End Function

Then the code for creating the image with the string as apart of it.

  'Set captchaText to what is generated in the function generateRandomString
  Dim captchaText As String = generateCaptchaString()

  'Creating a bitmap in memory
  Dim captchaBitmap As New Bitmap(200, 40)

  'Creating a Graphic so we can manipulate how the image will look
  Dim captchaGraphic As Graphics = Graphics.FromImage(captchaBitmap)

  Dim captchaFont As New Font("Arial", 14)

  'Set the Text color
  Dim captchaForeColor As New SolidBrush(Color.Blue)

  'Set the background color
  Dim captchaBackgroundColor As New SolidBrush(Color.Yellow)

  captchaGraphic.FillRectangle(captchaBackgroundColor, 0, 0, Width, Height)
  captchaGraphic.DrawString(captchaText, captchaFont, captchaForeColor, 5.0F, 5.0F)

  pict_Captcha.Image = captchaBitmap