如何解决Response.Flush在异步ASP.NET Web窗体页面中不起作用
我正在使用.Net Framework 4.8。 我正在构建一个网页,在单击按钮的PostBack事件后,该网页将重新计算化学制剂的成本,并从SQL Server获取数据。然后将计算出的价格存储回SQL Server,再通过HttpClient发送到SAP Hana服务器上的REST服务。
由于公式有1000多种(由数千行组件组成,有时会递归包括其他公式),并且必须将价格逐一发布到REST服务,所以我决定使页面成为多线程。
一切正常,我现在能够同时发布数十个价格,并且现在整个过程比同步完成要快得多。我无法做的是向呼叫者网页提供进度反馈。 这是我到目前为止尝试过的:
<%@ Page language="c#" Inherits="..." CodeFile="..." Async="true" AutoEventWireup="true" EnableSessionState="False" %>
在后面的代码中:
protected async void BtUpdatePricesSAP_Click(object sender,EventArgs e)
{
Response.Write(@"<!DOCTYPE HTML><html><head><title>Price update</title>...");
Response.Flush(); // Not working!!!
await ComputeEverything().ConfigureAwait(false);
Response.Write("<p>Done</p></body></html>");
Response.End();
}
private async Task ComputeEverything() {
using var cn = new SqlConnection((string)Application["dataSource"]);
//await cn.OpenAsync(); <= this does not work,throws an authentication error connecting to the db
cn.Open();
SqlCommand cmd = new SqlCommand("...",cn);
using (SqlDataReader dr = await cmd.ExecuteReaderAsync())
{
while (await dr.ReadAsync()) { ... }
...
// Here I store data in some collections,including a ConcurrentQueue<string> (name FormulationsIndex)
// and a ConcurrentDictionary (named FormulationRows) containing an array
// with the raw materials with quantities and prices.
}
// Then,I prepare the threads that will pop the formulations from the queue
// and call the recursive function that computes the costs:
async void FormulaProcessor() // local function
{
while (FormulationsIndex.TryDequeue(out string formulaCode))
await ComputeFormulaCostAsync(formulaCode,FormulationRows[formulaCode],1);
}
var tasks = new Task[15];
for (int i = 0; i < tasks.Length; i++)
tasks[i] = Task.Factory.StartNew(FormulaProcessor);
Task.WaitAll(tasks);
// here I update price to SQL from the ConcurrentDictionary where I stored them
while (Errors.TryDequeue(out string s)) // Errors is another ConcurrentQueue where I store the errors I found
Response.Write($"<p>{s}</p>");
}
private async Task<decimal> ComputeFormulaCostAsync(string formulaCode,Formula f,int recursionLevel)
{
if (Interlocked.Increment(ref processedCount) % 50 == 0)
{
int perc = (processedCount * 100 / totalFormulCount);
Response.Write($"<script>$('#progressBar').text('{perc}%').css('width','{perc}%').prop('aria-valuenow','{perc}');</script>");
Response.Flush(); ////////////// THIS DOES NOT WORK
// await Response.FlushAsync(); /////// THIS NEITHER!
}
decimal formulaCost = 0;
...
// here I iterate the formula components,calling this function recursively if the component is also a formulation
// Once done,I update the price of the current formulation in SAP
SapItemPricesHandler.SapItemPrice ip = new SapItemPricesHandler.SapItemPrice(formulaCost); // helper class to prepare the json for the REST post
var (httpStatusCode,responseContent) =
await SessionSL_Async.SendRequest($"Items('{formulaCode}')",new HttpMethod("PATCH"),ip.ToJson()).ConfigureAwait(false);
// SessionSL_Async is a static class I wrote to handle the REST communications with Hana using HttpClient
if (httpStatusCode != HttpStatusCode.NoContent)
Errors.Enqueue($"Errore scrittura prezzo in SAP,formula <b>{formulaCode}</b>,{responseContent}");
return formulaCost; // result value helps in recursive formulations,not needed in the main caller
}
我试图尽可能简化代码以使其清晰可见。该页面正常,我在Fiddler中看到了Hana的所有帖子。只是,我从Response.Write获得的所有反馈都会在完成所有处理后发生(在我的演示环境中需要几分钟)。我不明白为什么同花顺不起作用。
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