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搜尋 mathutil 結果:
.Net 6 的 Captcha 實做
產生 FileStreamResult 物件的 function 如下: (目前置於 SU 之中,以便轉移)

        static List<Brush> CaptchaBrushes = null;
        public static FileStreamResult CreateCaptcha(string captcha)
        {
            if (CaptchaBrushes == null)
            {
                CaptchaBrushes = new List<Brush>();
                CaptchaBrushes.Add(Brushes.White);
                CaptchaBrushes.Add(Brushes.Gold);
                CaptchaBrushes.Add(Brushes.LightSkyBlue);
                CaptchaBrushes.Add(Brushes.LimeGreen);
                CaptchaBrushes.Add(Brushes.AliceBlue);
                CaptchaBrushes.Add(Brushes.AntiqueWhite);
                CaptchaBrushes.Add(Brushes.BurlyWood);
                CaptchaBrushes.Add(Brushes.Silver);
            }

            int width = 90;
            int height = 45;

            //https://stackoverflow.com/questions/61365732/cannot-access-a-closed-stream-when-returning-filestreamresult-from-c-sharp-netc
            //Using statements close and unload the variable from memory set in the using statement which is why you are getting an error trying to access a closed memory stream.You don't need to use a using statement if you are just going to return the result at the end.

            //這個 memory stream 不用關閉或 dispose
            var ms = new MemoryStream();

            // 釋放所有在 GDI+ 所佔用的記憶體空間 ( 非常重要!! )
            using (Bitmap _bmp = new Bitmap(width, height))
            using (Graphics _graphics = Graphics.FromImage(_bmp))
            using (Font _font = new Font("Courier New", 24, FontStyle.Bold)) // _font 設定要出現在圖片上的文字字型、大小與樣式
            {
                // (封裝 GDI+ 繪圖介面) 所有繪圖作業都需透過 Graphics 物件進行操作
                _graphics.Clear(Color.Black);

                // 如果想啟用「反鋸齒」功能,可以將以下這行取消註解
                //_graphics.TextRenderingHint = TextRenderingHint.AntiAlias;

                // 將亂碼字串「繪製」到之前產生的 Graphics 「繪圖板」上
                var x = 10;
                for(var i = 0; i < captcha.Length; i++)
                {
                    _graphics.DrawString(captcha.Substring(i, 1), _font, CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], x, Su.MathUtil.GetRandomInt(15));
                    x += 10 + Su.MathUtil.GetRandomInt(10);
                }

                // 畫線
                
                _graphics.DrawLine(new Pen(CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], 1),
                    Su.MathUtil.GetRandomInt(0, Convert.ToInt32((width * 0.9 / 2))), 0, Su.MathUtil.GetRandomInt(Convert.ToInt32(width / 2), Convert.ToInt32(width * 1.9 / 2)), height);
                
                _graphics.DrawLine(new Pen(CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], 1),
                    Su.MathUtil.GetRandomInt(Convert.ToInt32(width / 2), Convert.ToInt32(width * 1.9 / 2)), 0, Su.MathUtil.GetRandomInt(0, Convert.ToInt32((width * 0.9 / 2))), height);
                
                _graphics.DrawLine(new Pen(CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], 1),
                    0,
                    Su.MathUtil.GetRandomInt(height / 2),
                    width,
                    height / 2 + Su.MathUtil.GetRandomInt(height / 2)
                    );

                _graphics.DrawLine(new Pen(CaptchaBrushes[Su.MathUtil.GetRandomInt(CaptchaBrushes.Count)], 1),
                 0,
                 height / 2 + Su.MathUtil.GetRandomInt(height / 2),
                 width,
                    Su.MathUtil.GetRandomInt(height / 2)
                 );

                _bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            }

            ms.Seek(0, SeekOrigin.Begin);

            // Controller 的型別為 FileResult
            return new FileStreamResult(ms, "image/jpeg")
            { FileDownloadName = $"{DateTime.Now.Ymdhmsf()}.jpg" };
        }



輸出用的 Controller 和 Action 如下:

namespace Web.Controllers
{
    public class CaptchaController : Controller
    {
        [Route("captcha")]
        public async Task<FileStreamResult> Index()
        {
            //產生 Captcha 並存入 Session 之中。目前是四位數字
            string captcha = (await Ah.ReGetAsync<object>("api/kol/create-captcha-code")).ToString();

            //產生圖檔並回傳 FileStreamResult
            return Su.Wu.CreateCaptcha(captcha);
        }
    }
}
More...
Bike, 2022/9/25 下午 10:03:44
Postgres 中使用 Transaction (TransactionScope) 必需要自已實做重試的功能
在 Postgres 使用 TransactionScope 似乎很空易就會發生 Transaction Abort 的情況。所以必需自行實做 retry 的機制

            int tries = 0;
            while (tries < Su.PgSql.maxTransactionAborted)
            {
                try
                {
                    using (var scop = new System.Transactions.TransactionScope(TransactionScopeAsyncFlowOption.Enabled))
                    {
                        var context = ShopBandContext.Context;

                        updateCount = await context.UpdateAsync<MarketDiscount>(dto, Sc.ModifyInfo,
                            onlyColumns: "StartAt,EndAt,NewPrice,FrontEndMemo,BackEndMemo");

                        scop.Complete();
                        break; //這個 Break 很重要
                    }
                }
                catch (Exception ex)
                {
                    // 我發現因為是非同步模式,所以要檢查很多層的 InnerException
                    if (tries < Su.PgSql.maxTransactionAborted
                        && ((ex.InnerException != null && ex.InnerException is Npgsql.PostgresException && ((Npgsql.PostgresException)ex.InnerException).SqlState == "40001")
                            || (ex.InnerException.InnerException != null && ex.InnerException.InnerException is Npgsql.PostgresException && ((Npgsql.PostgresException)ex.InnerException.InnerException).SqlState == "40001")))
                    {
                        //隨機休息 10 ~ 20 ms, 等另一個 job 完工
                        System.Threading.Thread.Sleep(Su.MathUtil.Random.Next(10, 20));
                        tries++;
                    }
                    else
                    {
                        throw;
                    }
                }
            }
More...
Bike, 2022/8/25 上午 09:19:35
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