asp.net core3.1 Actual combat development （ Encapsulation and use of captcha ）

<> encapsulation
public class VerifyCodeHelper { public static Bitmap CreateVerifyCode(out
string code) { // establish Bitmap object , mapping Bitmap bitmap = new Bitmap(200, 60); Graphics
graph= Graphics.FromImage(bitmap); graph.FillRectangle(new SolidBrush(Color.
White), 0, 0, 200, 60); Font font = new Font(FontFamily.GenericSerif, 48,
FontStyle.Bold, GraphicsUnit.Pixel); Random r = new Random(); string letters =
"ABCDEFGHIJKLMNPQRSTUVWXYZ0123456789"; StringBuilder sb = new StringBuilder();
// Add random five letters for (int x = 0; x < 5; x++) { string letter = letters.Substring(r.
Next(0, letters.Length - 1), 1); sb.Append(letter); graph.DrawString(letter,
font, new SolidBrush(Color.Black), x * 38, r.Next(0, 15)); } code = sb.ToString(
); // Confusing the background Pen linePen = new Pen(new SolidBrush(Color.Black), 2); for (int x = 0;
x< 6; x++) graph.DrawLine(linePen, new Point(r.Next(0, 199), r.Next(0, 59)),
new Point(r.Next(0, 199), r.Next(0, 59))); return bitmap; } }
use
public ActionResult VerifyCode() { string code = ""; Bitmap bitmap =
VerifyCodeHelper.CreateVerifyCode(out code); base.HttpContext.Session.SetString(
"CheckCode", code); MemoryStream stream = new MemoryStream(); bitmap.Save(stream
, ImageFormat.Gif); return File(stream.ToArray(), "image/gif"); }

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