AppDomain.FirstChanceException 事件

定義

命名空間:

System

組件:

System.Runtime.dll

來源:

AppDomain.cs

發生於執行階段在呼叫堆疊中搜尋應用程式定義域的例外狀況處理常式之前，在 Managed 程式碼中擲回例外狀況時。

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) 

事件類型

EventHandler<FirstChanceExceptionEventArgs>

範例

下列範例會透過 AD3 建立一系列名為 AD0 的應用程式域，並在每個應用程式域中都有 一個 Worker 物件。 每個 Worker 物件都有下一個應用程式域中物件的參考 Worker ，但最後一個應用程式域中的 除外 Worker 。 除了 之外，事件 FirstChanceException 會在所有應用程式域中 AD1 處理。

注意

除了此範例示範多個應用程式域中第一次發生例外狀況通知之外，您可以在 如何：接收First-Chance例外狀況通知中找到簡單的使用案例。

建立應用程式域之後，預設應用程式域會呼叫 TestException 第一個應用程式域的 方法。 每個 Worker 物件都會呼叫 TestException 下一個應用程式域的 方法，直到最後 Worker 一個擲回已處理或未處理的例外狀況為止。 因此，目前的執行緒會通過所有應用程式域，並 TestException 新增至每個應用程式域中的堆疊。

當最後一個 Worker 物件處理例外狀況時， FirstChanceException 事件只會在最後一個應用程式域中引發。 其他應用程式域永遠不會有機會處理例外狀況，因此不會引發事件。

當最後 Worker 一個物件未處理例外狀況時， FirstChanceException 事件會在具有事件處理常式的每個應用程式域中引發。 在每個事件處理常式完成之後，堆疊會繼續回溯，直到預設應用程式域攔截到例外狀況為止。

注意

若要查看堆疊顯示如何隨著事件更接近預設應用程式域而增加，請在事件處理常式中 FirstChanceHandler 變更 e.Exception.Message 為 e.Exception 。 請注意，當 跨應用程式域界限呼叫 時 TestException ，它會顯示兩次：一次用於 Proxy，一次用於存根。

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

備註

此事件只是通知。 處理此事件並不會處理例外狀況，也不會以任何方式影響後續的例外狀況處理。 引發事件並叫用事件處理常式之後，Common Language Runtime (CLR) 會開始搜尋例外狀況的處理常式。 FirstChanceException 提供應用程式域的第一個機會來檢查任何受控例外狀況。

每個應用程式域都可以處理事件。 如果在執行呼叫時執行緒通過多個應用程式域，則會在已註冊事件處理常式的每個應用程式域中引發事件，然後 CLR 開始搜尋該應用程式域中相符的例外狀況處理常式。 處理事件之後，就會搜尋該應用程式域中相符的例外狀況處理常式。 如果找不到事件，則會在下一個應用程式域中引發事件。

您必須處理事件事件處理常式 FirstChanceException 中發生的所有例外狀況。 否則， FirstChanceException 會以遞迴方式引發。 這可能會導致應用程式的堆疊溢位和終止。 我們建議您將此事件的事件處理常式實作為限制的執列區域， (CER) ，讓基礎結構相關的例外狀況，例如記憶體不足或堆疊溢位，以免在處理例外狀況通知時影響虛擬機器。

除非事件處理常式為安全性關鍵且具有 HandleProcessCorruptedStateExceptionsAttribute 屬性，否則不會針對指出進程狀態損毀的例外狀況引發此事件，例如存取違規。

Common Language Runtime 會在處理此通知事件時暫停執行緒中止。

另請參閱

• FirstChanceExceptionEventArgs
• UnhandledException
• 作法：接收第一個可能發生的例外狀況通知