通过PageMethods从javascript aspx页面调用时，C#死锁中的异步函数
问题摘要：通过PageMethods从javascript aspx页面调用时，C#死锁中的异步函数,c#,asp.net,asynchronous,async-await,pagemethods,C#,Asp.net,Asynchronous,Async Await,Pagemethods,问题摘要： 我正在尝试使用PageMethods从HTML页面调用C#函数。问题是我调用的C#函数被标记为异步，并将等待其他函数的完成。当PageMethods调用嵌套的异步C#函数时，C#代码似乎处于死锁状态。 我给出了一个ASP.NET页面的示例，后面用C#编码来说明我试图使用的习惯用法 示例WebForm1.aspx <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits
我正在尝试使用PageMethods从HTML页面调用C#函数。问题是我调用的C#函数被标记为异步，并将等待其他函数的完成。当PageMethods调用嵌套的异步C#函数时，C#代码似乎处于死锁状态。
我给出了一个ASP.NET页面的示例，后面用C#编码来说明我试图使用的习惯用法 示例WebForm1.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication3.WebForm1" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title></title></head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true"/>
<div>
<input type="button" value="Show Function timing" onclick="GetTiming()"/>
</div>
</form>
</body>
<script type="text/javascript">
function GetTiming() {
console.log("GetTiming function started.");
PageMethods.GetFunctionTiming(
function (response, userContext, methodName) { window.alert(response.Result); }
);
console.log("GetTiming function ended."); // This line gets hit!
}
</script>
</html>
using System;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Web.Services;
using System.Web.UI;
namespace WebApplication3
{
public partial class WebForm1 : Page
{
protected void Page_Load(object sender, EventArgs e) { }
[WebMethod]
public static async Task<string> GetFunctionTiming()
{
string returnString = "Start time: " + DateTime.Now.ToString();
Debug.WriteLine("Calling to business logic.");
await Task.Delay(1000); // This seems to deadlock
// Task.Delay(1000).Wait(); // This idiom would work if uncommented.
Debug.WriteLine("Business logic completed."); // This line doesn't get hit if we await the Task!
return returnString + "\nEnd time: "+ DateTime.Now.ToString();
}
}
}
using System;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Web.Services;
using System.Web.UI;
namespace WebApplication3
{
public partial class WebForm1 : Page
{
protected void Page_Load(object sender, EventArgs e) { }
[WebMethod]
public static async Task<string> GetFunctionTiming()
{
Debug.WriteLine("Shim function called.");
string returnString = "Start time: " + DateTime.Now.ToString();
// Here's the idiomatic shim that allows async calls from PageMethods
string myParameter = "\nEnd time: "; // Some parameter we're going to pass to the business logic
Task<string> myTask = Task.Run( () => BusinessLogicAsync(myParameter) ); // Avoid a deadlock problem by forcing the task onto the threadpool
string myResult = await myTask.ConfigureAwait(false); // Force the continuation onto the current (ASP.NET) context
Debug.WriteLine("Shim function completed. Returning result "+myResult+" to PageMethods call on web site...");
return returnString + myResult;
}
// This takes the place of some complex business logic that may nest deeper async calls
private static async Task<string> BusinessLogicAsync(string input)
{
Debug.WriteLine("Invoking business logic.");
string returnValue = await DeeperBusinessLogicAsync();
Debug.WriteLine("Business logic completed.");
return input+returnValue;
}
// Here's a simulated deeper async call
private static async Task<string> DeeperBusinessLogicAsync()
{
Debug.WriteLine("Invoking deeper business logic.");
await Task.Delay(1000); // This simulates a long-running async process
Debug.WriteLine("Deeper business logic completed.");
return DateTime.Now.ToString();
}
}
}
函数GetTiming（）{
log（“GetTiming函数已启动”）；
PageMethods.GetFunctionTimeing(
函数（response、userContext、methodName）{window.alert（response.Result）；}
);
log（“GetTiming函数已结束”）；//此行被命中！
}
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication3.WebForm1" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title></title></head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true"/>
<div>
<input type="button" value="Show Function timing" onclick="GetTiming()"/>
</div>
</form>
</body>
<script type="text/javascript">
function GetTiming() {
console.log("GetTiming function started.");
PageMethods.GetFunctionTiming(
function (response, userContext, methodName) { window.alert(response.Result); }
);
console.log("GetTiming function ended."); // This line gets hit!
}
</script>
</html>
using System;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Web.Services;
using System.Web.UI;
namespace WebApplication3
{
public partial class WebForm1 : Page
{
protected void Page_Load(object sender, EventArgs e) { }
[WebMethod]
public static async Task<string> GetFunctionTiming()
{
string returnString = "Start time: " + DateTime.Now.ToString();
Debug.WriteLine("Calling to business logic.");
await Task.Delay(1000); // This seems to deadlock
// Task.Delay(1000).Wait(); // This idiom would work if uncommented.
Debug.WriteLine("Business logic completed."); // This line doesn't get hit if we await the Task!
return returnString + "\nEnd time: "+ DateTime.Now.ToString();
}
}
}
using System;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Web.Services;
using System.Web.UI;
namespace WebApplication3
{
public partial class WebForm1 : Page
{
protected void Page_Load(object sender, EventArgs e) { }
[WebMethod]
public static async Task<string> GetFunctionTiming()
{
Debug.WriteLine("Shim function called.");
string returnString = "Start time: " + DateTime.Now.ToString();
// Here's the idiomatic shim that allows async calls from PageMethods
string myParameter = "\nEnd time: "; // Some parameter we're going to pass to the business logic
Task<string> myTask = Task.Run( () => BusinessLogicAsync(myParameter) ); // Avoid a deadlock problem by forcing the task onto the threadpool
string myResult = await myTask.ConfigureAwait(false); // Force the continuation onto the current (ASP.NET) context
Debug.WriteLine("Shim function completed. Returning result "+myResult+" to PageMethods call on web site...");
return returnString + myResult;
}
// This takes the place of some complex business logic that may nest deeper async calls
private static async Task<string> BusinessLogicAsync(string input)
{
Debug.WriteLine("Invoking business logic.");
string returnValue = await DeeperBusinessLogicAsync();
Debug.WriteLine("Business logic completed.");
return input+returnValue;
}
// Here's a simulated deeper async call
private static async Task<string> DeeperBusinessLogicAsync()
{
Debug.WriteLine("Invoking deeper business logic.");
await Task.Delay(1000); // This simulates a long-running async process
Debug.WriteLine("Deeper business logic completed.");
return DateTime.Now.ToString();
}
}
}
使用系统；
使用System.Threading.Tasks；
使用系统诊断；
使用System.Web.Services；
使用System.Web.UI；
命名空间WebApplication3
{
公共部分类WebForm1:第页
{
受保护的无效页面加载（对象发送方，事件参数e）{}
[网络方法]
公共静态异步任务GetFunctionTiming（）
{
string returnString=“开始时间：”+DateTime.Now.ToString（）；
WriteLine（“调用业务逻辑”）；
等待任务。延迟（1000）；//这似乎是死锁
//Task.Delay（1000.Wait（）；//如果没有注释，这个习惯用法就可以使用。
Debug.WriteLine（“业务逻辑完成”）；//如果我们等待任务，这一行不会被击中！
return returnString+“\nEnd time:”+DateTime.Now.ToString（）；
}
}
}
我绝对需要能够从我的网页UI调用异步代码。我想使用async/await功能来实现这一点，但我还没有弄清楚如何实现。我目前正在通过使用
Task.Wait（）Task.Result如何在PageMethods调用的上下文中等待服务器端异步函数
我真的，真的想了解在这里的封面下发生了什么，以及为什么从控制台应用程序调用异步方法时不会发生这种情况。这是因为默认情况下，
waitSynchronizationContextSynchronizationContext任务的线程上运行continuation（方法的剩余部分）。这通常是一个ThreadPool
线程
然而，这将解决您的死锁。记住这些危险，我建议一个更好的设计
await Task.Delay(1000).ConfigureAwait(false);
我找到了一种方法，允许PageMethods调用ASP.NET上的嵌套异步函数，而不会出现死锁。我的方法包括
使用ConfigureAwait（false），因此我们不会强制异步函数尝试返回原始捕获的上下文（Web UI线程将锁定该上下文）；及
将“顶级”异步函数强制到线程池中，而不是在ASP.NET的UI上下文中运行
这两种方法中的每一种都是论坛和博客上经常推荐的，所以我确信这两种方法都构成了一种反模式。但是，它确实允许使用PageMethods从ASP.NET网页调用异步函数。
示例C#代码如下所示。
示例WebForm1.aspx.cs
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication3.WebForm1" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title></title></head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true"/>
<div>
<input type="button" value="Show Function timing" onclick="GetTiming()"/>
</div>
</form>
</body>
<script type="text/javascript">
function GetTiming() {
console.log("GetTiming function started.");
PageMethods.GetFunctionTiming(
function (response, userContext, methodName) { window.alert(response.Result); }
);
console.log("GetTiming function ended."); // This line gets hit!
}
</script>
</html>
using System;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Web.Services;
using System.Web.UI;
namespace WebApplication3
{
public partial class WebForm1 : Page
{
protected void Page_Load(object sender, EventArgs e) { }
[WebMethod]
public static async Task<string> GetFunctionTiming()
{
string returnString = "Start time: " + DateTime.Now.ToString();
Debug.WriteLine("Calling to business logic.");
await Task.Delay(1000); // This seems to deadlock
// Task.Delay(1000).Wait(); // This idiom would work if uncommented.
Debug.WriteLine("Business logic completed."); // This line doesn't get hit if we await the Task!
return returnString + "\nEnd time: "+ DateTime.Now.ToString();
}
}
}
using System;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Web.Services;
using System.Web.UI;
namespace WebApplication3
{
public partial class WebForm1 : Page
{
protected void Page_Load(object sender, EventArgs e) { }
[WebMethod]
public static async Task<string> GetFunctionTiming()
{
Debug.WriteLine("Shim function called.");
string returnString = "Start time: " + DateTime.Now.ToString();
// Here's the idiomatic shim that allows async calls from PageMethods
string myParameter = "\nEnd time: "; // Some parameter we're going to pass to the business logic
Task<string> myTask = Task.Run( () => BusinessLogicAsync(myParameter) ); // Avoid a deadlock problem by forcing the task onto the threadpool
string myResult = await myTask.ConfigureAwait(false); // Force the continuation onto the current (ASP.NET) context
Debug.WriteLine("Shim function completed. Returning result "+myResult+" to PageMethods call on web site...");
return returnString + myResult;
}
// This takes the place of some complex business logic that may nest deeper async calls
private static async Task<string> BusinessLogicAsync(string input)
{
Debug.WriteLine("Invoking business logic.");
string returnValue = await DeeperBusinessLogicAsync();
Debug.WriteLine("Business logic completed.");
return input+returnValue;
}
// Here's a simulated deeper async call
private static async Task<string> DeeperBusinessLogicAsync()
{
Debug.WriteLine("Invoking deeper business logic.");
await Task.Delay(1000); // This simulates a long-running async process
Debug.WriteLine("Deeper business logic completed.");
return DateTime.Now.ToString();
}
}
}
使用系统；
使用System.Threading.Tasks；
使用系统诊断；
使用System.Web.Services；
使用System.Web.UI；
命名空间WebApplication3
{
公共部分类WebForm1:第页
{
受保护的无效页面加载（对象发送方，事件参数e）{}
[网络方法]
公共静态异步任务GetFunctionTiming（）
{
WriteLine（“调用了Shim函数”）；
string returnString=“开始时间：”+DateTime.Now.ToString（）；
//下面是一个惯用的垫片，它允许从PageMethods进行异步调用
string myParameter=“\nEnd time:”；//我们要传递给业务逻辑的一些参数
Task myTask=Task.Run（（）=>BusinessLogicAsync（myParameter））；//通过将任务强制到线程池中来避免死锁问题
string myResult=await myTask.ConfigureAwait（false）；//强制在当前（ASP.NET）上下文中继续
Debug.WriteLine（“填隙函数已完成。将结果“+myResult+”返回到网站上的PageMethods调用…”）；
返回returnString+myResult；
}
//这将取代一些可能嵌套更深层次异步调用的复杂业务逻辑
专用静态异步任务BusinessLogicAsync（字符串输入）
{
WriteLine（“调用业务逻辑”）；
string returnValue=await DeeperBusinessLogicAsync（）；
WriteLine（“业务逻辑完成”）；
返回输入+返回值；
}
//下面是一个模拟的更深层次的异步调用
专用静态异步任务DeeperBusinessLogicAsync（）
{
WriteLine（“调用更深层的业务逻辑”）；
wait Task.Delay（1000）；//这模拟了一个长期运行的异步进程
WriteLine（“完成了更深层次的业务逻辑”）；
return DateTime.Now.ToString（）；
}
}
}
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