在asp.net中下載SQL備份檔案

我正在嘗試下載 sql 備份檔案，但出現錯誤：“無法評估運算式，因為代碼已優化或本機框架位于呼叫堆疊頂部”靠近 respone.end()

protected void btnDownload_Click(object sender, EventArgs e)
    {
        try
        {
            string backupDestination = backupPath;
            string dbNAme = dbName;
            string dateStamp = DateTime.Now.ToString("yy-MM-dd@HHmm");
            string backupfile = backupDestination   '\\'   dbNAme   " of "   dateStamp   ".bak";

            DataTable dt = blu.queryFunction("BACKUP database "   dbNAme   " to disk='"   backupDestination   "\\"   dbNAme   " of "   dateStamp   ".Bak'");

            WebClient req = new WebClient();
            HttpResponse response = HttpContext.Current.Response;

            response.Clear();
            response.ClearContent();
            response.ClearHeaders();
            response.Buffer = true;

            response.AddHeader("content-disposition", "attachment; filename= "   dbNAme   ".bak");
            
            byte[] data = req.DownloadData(backupfile);
            response.ContentType = "application/sql";
            response.BinaryWrite(data);
            response.End();
        }
        catch (Exception ex)
        {
            ScriptManager.RegisterStartupScript(this, this.GetType(), "alertscipt", "swal('Error!','Database Backup Failed."   ex.ToString()   "','warning')", true);
        }
    }

uj5u.com熱心網友回復：

我看到的一個問題是緩沖區 - 將 the 更改response.Buffer = true;為 false

response.Buffer = false;

對于大檔案，這是錯誤的，因為它將它放在緩沖區中，但您想將其直接發送給用戶...

還要洗掉catch (Exception ex)以查看代碼中的其他問題 -ScriptManager.RegisterStartupScript從更改標題的那一刻起就不會運行。所以這個問題對你是隱藏的。

另一種更好、更正確的方法是創建一個處理程式并從那里下載檔案。

uj5u.com熱心網友回復：

如果運行應用程式的服務器上存在備份檔案，則不應使用 WebClient。從本地磁盤讀取檔案的東西，例如 TransmitFile()，就足夠了 - 像這樣：

string backupDestination = backupPath;
string dbNAme = dbName;
string dateStamp = DateTime.Now.ToString("yy-MM-dd@HHmm");
string backupfile = backupDestination   '\\'   dbNAme   " of "   dateStamp   ".bak";

DataTable dt = blu.queryFunction("BACKUP database "   dbNAme   " to disk='"   backupDestination   "\\"   dbNAme   " of "   dateStamp   ".Bak'");

HttpResponse response = HttpContext.Current.Response;

response.Clear();
response.ClearContent();
response.ClearHeaders();
response.Buffer = true;

response.AddHeader("content-disposition", "attachment; filename= "   dbNAme   ".bak");

response.ContentType = "application/octet-stream";
response.TransmitFile(backupfile);
response.Flush();

uj5u.com熱心網友回復：

好的，72 小時后我發現了錯誤。下載按鈕位于更新面板內，因此我收到“無法評估運算式，因為代碼已優化或本機框架位于呼叫堆疊頂部”

protected void btnDownload_Click(object sender, EventArgs e)
    {
        try
        {
            string dbNAme = dbName;
            string backupDestination = Server.MapPath("~/BackUp");
            string dateStamp = DateTime.Now.ToString("yyyy-MM-dd@HH_mm");
            string fileName = dbName   " of "   dateStamp   ".Bak";

            if (!Directory.Exists(backupDestination))
            {
                Directory.CreateDirectory(backupDestination);
            }

            DataTable dt = blu.queryFunction("BACKUP database "   dbNAme   " to disk='"   backupDestination   "\\"   fileName   "'");


            byte[] bytes = File.ReadAllBytes(Path.Combine(backupDestination, fileName));
            // Delete .bak file from server folder.
            if (Directory.Exists(backupDestination))
            {
                Directory.Delete(backupDestination, true);
            }
            Response.Clear();
            Response.Buffer = false;
            Response.Charset = "";
            Response.Cache.SetCacheability(HttpCacheability.NoCache);
            Response.ContentType = "application/octet-stream";
            Response.AppendHeader("Content-Disposition", "attachment; filename="   fileName);
            Response.BinaryWrite(bytes);
            Response.Flush();
            Response.End();
        }
        catch(Exception ex)
        {
            string exception = ex.ToString();
        }            
    }

標籤：asp.net sql-server

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