AppDomain.FirstChanceException 事件

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

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

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

[add: System.Security.SecurityCritical]
[remove: System.Security.SecurityCritical]
public event EventHandler<System.Runtime.ExceptionServices.FirstChanceExceptionEventArgs> FirstChanceException;

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

[<add: System.Security.SecurityCritical>]
[<remove: System.Security.SecurityCritical>]
member this.FirstChanceException : EventHandler<System.Runtime.ExceptionServices.FirstChanceExceptionEventArgs> 

Public Custom Event FirstChanceException As EventHandler(Of FirstChanceExceptionEventArgs) 

事件類型

屬性

SecurityCriticalAttribute

範例

以下範例建立一系列以 為 AD0 命名的 AD3應用域，每個應用域中都有一個 Worker 物件。 每個 Worker 物件都有指向下一個應用域的物件 Worker 的參考，唯獨最後一個應用程式域中的物件 Worker 例外。 FirstChanceException該AD1事件在除 之外的所有應用域中都被處理。

當應用程式網域建立完成後，預設的應用程式域會呼叫 TestException 第一個應用程式網域的方法。 每個 Worker 物件會呼叫下一個應用程式域的方法 TestException ，直到最後一個 Worker 拋出一個異常，該異常可能是處理中或未處理。 因此，目前執行緒會經過所有應用域，並 TestException 加入每個應用域的堆疊。

當最後一個 Worker 物件處理例外時， FirstChanceException 事件只會在最後一個應用程式域中被觸發。 其他應用域從未有機會處理這個例外，因此事件不會被觸發。

當最後一個 Worker 物件未處理例外時， FirstChanceException 該事件會在每個有事件處理程序的應用域中被觸發。 每個事件處理程序完成後，堆疊會持續展開，直到例外被預設的應用程式域捕捉為止。

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

備註

這個事件只是通知。 處理此事件不會處理該例外，也不影響後續的例外處理。 事件被提出且事件處理程序被呼叫後，通用語言執行時（CLR）開始尋找該例外的處理程序。 FirstChanceException 讓應用程式領域有優先檢視任何受管理例外的機會。

事件可依應用程式域處理。 如果執行緒在執行呼叫時經過多個應用程式域，該事件會在每個註冊事件處理程序的應用程式域中被觸發，然後 CLR 才開始搜尋該領域中匹配的例外處理程序。 事件處理完成後，會搜尋該應用域中匹配的例外處理程序。 若未找到，則在下一個應用域中觸發該事件。

你必須處理該事件處理 FirstChanceException 程序中出現的所有例外。 否則， FirstChanceException 則是遞迴提升。 這可能導致堆疊溢位並終止應用程式。 我們建議您為此事件實作受限執行區域（CER）的事件處理程序，以防止基礎設施相關的例外（如記憶體不足或堆疊溢位）在例外通知處理過程中影響虛擬機器。

除非事件處理程序具有安全性關鍵且擁有該 HandleProcessCorruptedStateExceptionsAttribute 屬性，否則不會因表示程序狀態損壞的例外（如存取違規）而觸發此事件。

通用語言執行時會在處理此通知事件時暫停執行緒中止。

另請參閱

• FirstChanceExceptionEventArgs
• UnhandledException
• 如何：接收 First-Chance 例外通知