AppDomain.FirstChanceException 事件

定义

命名空间:

System

程序集:

System.Runtime.dll

Source:

AppDomain.cs

当托管代码抛出异常时发生，在运行时在调用堆栈中搜索应用程序域中的异常处理程序之前。

public:
 event EventHandler<System::Runtime::ExceptionServices::FirstChanceExceptionEventArgs ^> ^ FirstChanceException;

public event EventHandler<System.Runtime.ExceptionServices.FirstChanceExceptionEventArgs>? FirstChanceException;

member this.FirstChanceException : EventHandler<System.Runtime.ExceptionServices.FirstChanceExceptionEventArgs> 

Public Custom Event FirstChanceException As EventHandler(Of FirstChanceExceptionEventArgs) 

事件类型

EventHandler<FirstChanceExceptionEventArgs>

示例

以下示例通过 AD3创建一系列名为 AD0 的应用程序域，每个应用程序域中都有一个 Worker 对象。 每个对象都有 Worker 对 Worker 下一个应用程序域中的 对象的引用，但最后一个应用程序域中的 除外 Worker 。 事件 FirstChanceException 在除 之外 AD1的所有应用程序域中进行处理。

注意

除了此示例演示多个应用程序域中的第一机会异常通知外，还可以在 如何：接收First-Chance异常通知中找到简单的用例。

创建应用程序域后，默认应用程序域将调用 TestException 第一个应用程序域的 方法。 每个对象都会 Worker 为下一个应用程序域调用 TestException 方法，直到最后 Worker 一个对象引发已处理或未处理的异常。 因此，当前线程通过所有应用程序域，并 TestException 添加到每个应用程序域中的堆栈。

当最后一个 Worker 对象处理异常时 FirstChanceException ，事件仅在最后一个应用程序域中引发。 其他应用程序域永远不会有机会处理异常，因此不会引发事件。

当最后一个 Worker 对象不处理异常时，事件 FirstChanceException 在具有事件处理程序的每个应用程序域中引发。 每个事件处理程序完成后，堆栈将继续展开，直到默认应用程序域捕获异常。

注意

若要查看随着事件越来越靠近默认应用程序域而引发的堆栈显示如何增长，请在事件处理程序中FirstChanceHandler更改为 e.Exception.Messagee.Exception 。 请注意，当跨应用程序域边界调用 时 TestException ，它会出现两次：一次用于代理，一次用于存根。

using System;
using System.Reflection;
using System.Runtime.ExceptionServices;

class FirstChanceExceptionSnippet
{
    static void Main()
    {
        AppDomain.CurrentDomain.FirstChanceException += FirstChanceHandler;

        // Create a set of application domains, with a Worker object in each one.
        // Each Worker object creates the next application domain.
        AppDomain ad = AppDomain.CreateDomain("AD0");
        Worker w = (Worker) ad.CreateInstanceAndUnwrap(
                                typeof(Worker).Assembly.FullName, "Worker");
        w.Initialize(0, 3);

        Console.WriteLine("\r\nThe last application domain throws an exception and catches it:");
        Console.WriteLine();
        w.TestException(true);

        try
        {
            Console.WriteLine(
                "\r\nThe last application domain throws an exception and does not catch it:");
            Console.WriteLine();
            w.TestException(false);
        }
        catch (ArgumentException ex)
        {
            Console.WriteLine("ArgumentException caught in {0}: {1}",
                AppDomain.CurrentDomain.FriendlyName, ex.Message);
        }
    }

    static void FirstChanceHandler(object source, FirstChanceExceptionEventArgs e)
    {
        Console.WriteLine("FirstChanceException event raised in {0}: {1}",
            AppDomain.CurrentDomain.FriendlyName, e.Exception.Message);
    }
}

public class Worker : MarshalByRefObject
{
    private AppDomain ad = null;
    private Worker w = null;

    public void Initialize(int count, int max)
    {
        // Handle the FirstChanceException event in all application domains except
        // AD1.
        if (count != 1)
        {
            AppDomain.CurrentDomain.FirstChanceException += FirstChanceHandler;
        }

        // Create another application domain, until the maximum is reached.
        // Field w remains null in the last application domain, as a signal
        // to TestException().
        if (count < max)
        {
            int next = count + 1;
            ad = AppDomain.CreateDomain("AD" + next);
            w = (Worker) ad.CreateInstanceAndUnwrap(
                             typeof(Worker).Assembly.FullName, "Worker");
            w.Initialize(next, max);
        }
    }

    public void TestException(bool handled)
    {
        // As long as there is another application domain, call TestException() on
        // its Worker object. When the last application domain is reached, throw a
        // handled or unhandled exception.
        if (w != null)
        {
            w.TestException(handled);
        }
        else if (handled)
        {
            try
            {
                throw new ArgumentException("Thrown in " + AppDomain.CurrentDomain.FriendlyName);
            }
            catch (ArgumentException ex)
            {
                Console.WriteLine("ArgumentException caught in {0}: {1}",
                    AppDomain.CurrentDomain.FriendlyName, ex.Message);
            }
        }
        else
        {
            throw new ArgumentException("Thrown in " + AppDomain.CurrentDomain.FriendlyName);
        }
    }

    static void FirstChanceHandler(object source, FirstChanceExceptionEventArgs e)
    {
        Console.WriteLine("FirstChanceException event raised in {0}: {1}",
            AppDomain.CurrentDomain.FriendlyName, e.Exception.Message);
    }
}

/* This example produces output similar to the following:

The last application domain throws an exception and catches it:

FirstChanceException event raised in AD3: Thrown in AD3
ArgumentException caught in AD3: Thrown in AD3

The last application domain throws an exception and does not catch it:

FirstChanceException event raised in AD3: Thrown in AD3
FirstChanceException event raised in AD2: Thrown in AD3
FirstChanceException event raised in AD0: Thrown in AD3
FirstChanceException event raised in Example.exe: Thrown in AD3
ArgumentException caught in Example.exe: Thrown in AD3
 */

open System
open System.Runtime.ExceptionServices

let firstChanceHandler _ (e: FirstChanceExceptionEventArgs) =
    printfn $"FirstChanceException event raised in {AppDomain.CurrentDomain.FriendlyName}: {e.Exception.Message}"

type Worker() =
    inherit MarshalByRefObject()

    let mutable w = Unchecked.defaultof<Worker>

    member _.Initialize(count, max) =
        // Handle the FirstChanceException event in all application domains except
        // AD1.
        if count <> 1 then
            AppDomain.CurrentDomain.FirstChanceException.AddHandler firstChanceHandler

        // Create another application domain, until the maximum is reached.
        // Field w remains null in the last application domain, as a signal
        // to TestException().
        if count < max then
            let next = count + 1
            let ad = AppDomain.CreateDomain("AD" + string next)
            w <-
                ad.CreateInstanceAndUnwrap(typeof<Worker>.Assembly.FullName, "Worker") :?> Worker
            w.Initialize(next, max)

    member _.TestException(handled) =
        // As long as there is another application domain, call TestException() on
        // its Worker object. When the last application domain is reached, throw a
        // handled or unhandled exception.
        if isNull (box w) then
            w.TestException handled
        elif handled then
            try
                raise (ArgumentException $"Thrown in {AppDomain.CurrentDomain.FriendlyName}")
            with :? ArgumentException as ex ->
                printfn $"ArgumentException caught in {AppDomain.CurrentDomain.FriendlyName}: {ex.Message}"
        else
            raise (ArgumentException $"Thrown in {AppDomain.CurrentDomain.FriendlyName}")

AppDomain.CurrentDomain.FirstChanceException.AddHandler firstChanceHandler

// Create a set of application domains, with a Worker object in each one.
// Each Worker object creates the next application domain.
let ad = AppDomain.CreateDomain "AD0"
let w = ad.CreateInstanceAndUnwrap(typeof<Worker>.Assembly.FullName, "Worker") :?> Worker
w.Initialize(0, 3)

printfn "\nThe last application domain throws an exception and catches it:\n"
w.TestException true

try
    printfn "\nThe last application domain throws an exception and does not catch it:\n"
    w.TestException false
with :? ArgumentException as ex ->
    printfn"ArgumentException caught in {AppDomain.CurrentDomain.FriendlyName}: {ex.Message}"

(* This example produces output similar to the following:

The last application domain throws an exception and catches it:

FirstChanceException event raised in AD3: Thrown in AD3
ArgumentException caught in AD3: Thrown in AD3

The last application domain throws an exception and does not catch it:

FirstChanceException event raised in AD3: Thrown in AD3
FirstChanceException event raised in AD2: Thrown in AD3
FirstChanceException event raised in AD0: Thrown in AD3
FirstChanceException event raised in Example.exe: Thrown in AD3
ArgumentException caught in Example.exe: Thrown in AD3
 *)

Imports System.Reflection
Imports System.Runtime.ExceptionServices

Class Example

    Shared Sub Main()
    
        AddHandler AppDomain.CurrentDomain.FirstChanceException, AddressOf FirstChanceHandler

        ' Create a set of application domains, with a Worker object in each one.
        ' Each Worker object creates the next application domain.
        Dim ad As AppDomain = AppDomain.CreateDomain("AD0")
        Dim w As Worker = CType(ad.CreateInstanceAndUnwrap(
                                GetType(Worker).Assembly.FullName, "Worker"),
                                Worker)
        w.Initialize(0, 3)

        Console.WriteLine(vbCrLf & "The last application domain throws an exception and catches it:")
        Console.WriteLine()
        w.TestException(true)

        Try
            Console.WriteLine(vbCrLf & 
                "The last application domain throws an exception and does not catch it:")
            Console.WriteLine()
            w.TestException(false) 

        Catch ex As ArgumentException
        
            Console.WriteLine("ArgumentException caught in {0}: {1}", 
                AppDomain.CurrentDomain.FriendlyName, ex.Message)
        End Try
    End Sub

    Shared Sub FirstChanceHandler(ByVal source As Object, 
                                  ByVal e As FirstChanceExceptionEventArgs)
    
        Console.WriteLine("FirstChanceException event raised in {0}: {1}",
            AppDomain.CurrentDomain.FriendlyName, e.Exception.Message)
    End Sub
End Class

Public Class Worker
    Inherits MarshalByRefObject

    Private ad As AppDomain = Nothing
    Private w As Worker = Nothing

    Public Sub Initialize(ByVal count As Integer, ByVal max As Integer)
    
        ' Handle the FirstChanceException event in all application domains except
        ' AD1.
        If count <> 1
        
            AddHandler AppDomain.CurrentDomain.FirstChanceException, AddressOf FirstChanceHandler

        End If

        ' Create another application domain, until the maximum is reached.
        ' Field w remains Nothing in the last application domain, as a signal 
        ' to TestException(). 
        If count < max
            Dim nextAD As Integer = count + 1
            ad = AppDomain.CreateDomain("AD" & nextAD)
            w = CType(ad.CreateInstanceAndUnwrap(
                      GetType(Worker).Assembly.FullName, "Worker"),
                      Worker)
            w.Initialize(nextAD, max)
        End If
    End Sub

    Public Sub TestException(ByVal handled As Boolean)
    
        ' As long as there is another application domain, call TestException() on
        ' its Worker object. When the last application domain is reached, throw a
        ' handled or unhandled exception.
        If w IsNot Nothing
        
            w.TestException(handled)

        Else If handled
        
            Try
                Throw New ArgumentException("Thrown in " & AppDomain.CurrentDomain.FriendlyName)

            Catch ex As ArgumentException
            
                Console.WriteLine("ArgumentException caught in {0}: {1}", 
                    AppDomain.CurrentDomain.FriendlyName, ex.Message)
            End Try
        Else
        
            Throw New ArgumentException("Thrown in " & AppDomain.CurrentDomain.FriendlyName)
        End If
    End Sub

    Shared Sub FirstChanceHandler(ByVal source As Object, 
                                  ByVal e As FirstChanceExceptionEventArgs)
    
        Console.WriteLine("FirstChanceException event raised in {0}: {1}",
            AppDomain.CurrentDomain.FriendlyName, e.Exception.Message)
    End Sub
End Class

' This example produces output similar to the following:
'
'The last application domain throws an exception and catches it:
'
'FirstChanceException event raised in AD3: Thrown in AD3
'ArgumentException caught in AD3: Thrown in AD3
'
'The last application domain throws an exception and does not catch it:
'
'FirstChanceException event raised in AD3: Thrown in AD3
'FirstChanceException event raised in AD2: Thrown in AD3
'FirstChanceException event raised in AD0: Thrown in AD3
'FirstChanceException event raised in Example.exe: Thrown in AD3
'ArgumentException caught in Example.exe: Thrown in AD3

注解

此事件只是通知。 处理此事件不会以任何方式处理异常或影响后续异常处理。 引发事件并调用事件处理程序后，公共语言运行时 (CLR) 开始搜索异常的处理程序。 FirstChanceException 为应用程序域提供了检查任何托管异常的第一次机会。

事件可以按应用程序域进行处理。 如果线程在执行调用时通过多个应用程序域，则在 CLR 开始搜索该应用程序域中匹配的异常处理程序之前，事件将在已注册事件处理程序的每个应用程序域中引发。 处理事件后，将搜索该应用程序域中匹配的异常处理程序。 如果未找到，则会在下一个应用程序域中引发该事件。

必须处理事件事件处理程序 FirstChanceException 中发生的所有异常。 否则， FirstChanceException 以递归方式引发。 这可能会导致堆栈溢出和应用程序终止。 建议将此事件的事件处理程序实现为受约束的执行区域 (CER) ，以便在处理异常通知时防止与基础结构相关的异常（如内存不足或堆栈溢出）影响虚拟机。

对于指示进程状态损坏（例如访问冲突）的异常，不会引发此事件，除非事件处理程序是安全关键型的并且具有 HandleProcessCorruptedStateExceptionsAttribute 属性。

公共语言运行时在处理此通知事件时暂停线程中止。

另请参阅

• FirstChanceExceptionEventArgs
• UnhandledException
• 如何：接收第一机会异常通知