錯誤不被逮住

我寫了一個上傳xml文件的腳本，看看下面的代碼片段：錯誤不被逮住

open System.Xml 
open System.IO 
open System 

type XmlErrorLoad = 
    | Success of XmlDocument 
    | FileNotFound of FileNotFoundException 
    | OtherException of Exception 

let doc (filename:string) = 
    try 
     let file = XmlDocument() 
     file.Load(filename) 
     Success file 
    with 
    | :? FileNotFoundException as ex -> FileNotFound ex 
    | :? Exception as ex -> OtherException ex 


let fileNotExists = doc("C:\Temp\ip2.xml") 
match fileNotExists with 
| Success s ->() 
| FileNotFound ex -> printfn "File not found: %s" ex.Message 
| OtherException ex -> printfn "Exception: %s" ex.Message

在這種情況下，ip2.xml文件不存在，它應該拋出一個錯誤FileNotFound並在屏幕上打印。

"File not found: %s" ex.Message

但我得到的消息

val fileNotExists : XmlErrorLoad = 
    FileNotFound 
    System.IO.FileNotFoundException: Could not find file 'C:\Temp\ip2.xml'. 
File name: 'C:\Temp\ip2.xml' 
    at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) 
    at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost) 
    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize) 
    at System.Xml.XmlDownloadManager.GetStream(Uri uri, ICredentials credentials, IWebProxy proxy, RequestCachePolicy cachePolicy) 
    at System.Xml.XmlUrlResolver.GetEntity(Uri absoluteUri, String role, Type ofObjectToReturn) 
    at System.Xml.XmlTextReaderImpl.OpenUrlDelegate(Object xmlResolver) 
    at System.Threading.CompressedStack.runTryCode(Object userData) 
    at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) 
    at System.Threading.CompressedStack.Run(CompressedStack compressedStack, ContextCallback callback, Object state) 
    at System.Xml.XmlTextReaderImpl.OpenUrl() 
    at System.Xml.XmlTextReaderImpl.Read() 
    at System.Xml.XmlLoader.Load(XmlDocument doc, XmlReader reader, Boolean preserveWhitespace) 
    at System.Xml.XmlDocument.Load(XmlReader reader) 
    at System.Xml.XmlDocument.Load(String filename) 
    at FSI_0004.doc(String filename) in D:\f#\samples\ip.fsx:line 20

來源

2015-02-12 zero_coding

我試過你的代碼作爲F＃交互式輸入，並獲得所需的信息

File not found: Could not find file 'C:\Temp\ip2.xml'.

除了輸出F＃互動名單代碼中定義的所有值，所以我還得到以下印刷品：

type XmlErrorLoad = 
    | Success of XmlDocument 
    | FileNotFound of FileNotFoundException 
    | OtherException of Exception 
val doc : filename:string -> XmlErrorLoad 
val fileNotExists : XmlErrorLoad = 
    FileNotFound 
    System.IO.FileNotFoundException: Could not find file 'C:\Temp\ip2.xml'. 
File name: 'C:\Temp\ip2.xml' 
    at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) 
    at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost) 
    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize) 
    at System.Xml.XmlDownloadManager.GetStream(Uri uri, ICredentials credentials, IWebProxy proxy, RequestCachePolicy cachePolicy) 
    at System.Xml.XmlUrlResolver.GetEntity(Uri absoluteUri, String role, Type ofObjectToReturn) 
    at System.Xml.XmlTextReaderImpl.OpenUrlDelegate(Object xmlResolver) 
    at System.Threading.CompressedStack.runTryCode(Object userData) 
    at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData) 
    at System.Threading.CompressedStack.Run(CompressedStack compressedStack, ContextCallback callback, Object state) 
    at System.Xml.XmlTextReaderImpl.OpenUrl() 
    at System.Xml.XmlTextReaderImpl.Read() 
    at System.Xml.XmlLoader.Load(XmlDocument doc, XmlReader reader, Boolean preserveWhitespace) 
    at System.Xml.XmlDocument.Load(XmlReader reader) 
    at System.Xml.XmlDocument.Load(String filename) 
    at FSI_0003.doc(String filename) 
val it : unit =()

您只在F＃Interactive中獲得此輸出，作爲REPL反饋的一部分。在一個正常的程序中，這個輸出不會被生成。

來源

2015-02-12 06:42:12

錯誤不被逮住

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