F＃異常未被捕獲正確

Question

我有一個F＃異常，它沒有被捕獲到正確的catch塊中。

下面是相關代碼：

exception ConfigFileVersionIncompatabilityException of string 

[<XmlType("config")>] 
type Configuration() = class 

    let thisVersion : string = "1.0" 
    let mutable fileVersion : string = thisVersion 

    [<XmlAttribute("version")>] 
    member x.FileVersion 
     with get() = fileVersion 
     and set v = if v <> thisVersion 
        then raise (ConfigFileVersionIncompatabilityException(String.Format("Was expecting version {0} but read version {1}.", thisVersion, v))) 
end 


module FilterFileFunctions = 

    let sampleConfigFilename = "sample.filters" 

    let readConfig (file : string) = 
     try 
      use xmlDoc = new StreamReader(file) in 
       let s = XmlSerializer(typeof<Configuration>) 
       s.Deserialize(xmlDoc) :?> Configuration |> Success 
     with 
     | ConfigFileVersionIncompatabilityException(s) -> 
      String.Format("Failed to read the configuration file: \"{0}\";\nThe following reason was given:\n{1}", file, s) 
      |> Failure 
     | ex -> 
      String.Format("Failed to read the configuration file: \"{0}\";\n{1}", file, ex) 
      |> Failure 

的問題是，ex catch塊捕捉ConfigFileVersionIncompatabilityException例外，它應該由第一次塊被捕獲。

我試圖用:? System.Exception as ex而不是ex，它仍然表現相同。

我錯過了什麼嗎？

[主編1初始後之後分鐘以除去無關的代碼。]

Answer 1

當異常的反序列化過程發生時，Deserialize方法會抓住它，敷內部InvalidOperationException。這意味着您需要與InvalidOperationException進行溝通，然後分析InnerException屬性以獲取用戶定義的異常。

try // .. 
with 
| :? InvalidOperationException as invOp -> 
    match inv.InnerException with 
    | :? ConfigFileVersionIncompatabilityException as e -> 
    printfn "%s" e.Data0 
    | _ -> // generic handler 
| e -> // generic handler 

的Data0屬性公開由異常（I使用它，因爲可以不容易在圖案匹配使用:?時訪問它）承載的值。但是，您可以使用主動模式避免match表達醜陋嵌套（和通用處理器的重複）：

let (|InnerException|) (e:exn) = 
    e.InnerException 

try // .. 
with 
| InnerException(ConfigFileVersionIncompatabilityException s) -> 
    printfn "%s" s 
| _ -> // generic handler