知道抛出异常的方法

Question

我正在从xml文件中读取信息，在某个时刻，两条Boolean.Parse()指令可能会引发异常

考虑到整个代码段已经在try语句下，我想把所有的catch放在一个地方，而不是把上面的两个方法调用放在其他的try-catch下。

我的问题是，我如何才能知道是哪个方法抛出了异常？我必须显示不同的错误消息，这取决于谁未能转换。

try
{
    XmlNode db = _xml.SelectSingleNode("root/database");

    string usr = db.SelectSingleNode("username").InnerText;
    string psw = db.SelectSingleNode("password").InnerText;
    string srvr = db.SelectSingleNode("server").InnerText;
    string dbn = db.SelectSingleNode("dbname").InnerText;
    //Here a FormatException can be thrown by both these Parse()
    //And I need to know which is the caller in order to display the correct error message
    bool clean_db = Boolean.Parse(db.Attributes["clean"].Value);
    bool functions = Boolean.Parse(db.Attributes["insertFunctions"].Value);

    return new DatabaseConfiguration(usr, psw, srvr, dbn, clean_db, functions);
}
catch (XPathException)
{
    Console.WriteLine("<database> node is missing");
}
catch(FormatException e)
{
    //Here I'm supposed to do something to get the caller
    Console.WriteLine("Error message");
}

Answer 1

在每个boolean.parse方法周围添加一个额外的try/catch，然后使catch为：

try
{
    XmlNode db = _xml.SelectSingleNode("root/database");

    string usr = db.SelectSingleNode("username").InnerText;
    string psw = db.SelectSingleNode("password").InnerText;
    string srvr = db.SelectSingleNode("server").InnerText;
    string dbn = db.SelectSingleNode("dbname").InnerText;
    //Here a FormatException can be thrown by both these Parse()
    //And I need to know which is the caller in order to display the correct error message
    bool clean_db;
        try
        {
            clean_db = Boolean.Parse(db.Attributes["clean"].Value);
        }
        catch
        {
            throw new Exception ("clean exception");
        }
        bool functions;
        try
        {
            functions = Boolean.Parse(db.Attributes["insertFunctions"].Value);
        }
        catch
        {
            throw new Exception ("function exception");
        }
        return new DatabaseConfiguration(usr, psw, srvr, dbn, clean_db, functions);
    }
    catch (XPathException)
    {
        Console.WriteLine("<database> node is missing");
    }
    catch(FormatException e)
    {
        //Here I'm supposed to do something to get the caller
        Console.WriteLine("Error message");
    }

那么外部catch将告诉异常来自哪一行。

然后修改外部catch以显示异常消息。

以下是Steve的建议，因为他告诉我更新我的答案：）

try
{
    XmlNode db = _xml.SelectSingleNode("root/database");

    string usr = db.SelectSingleNode("username").InnerText;
    string psw = db.SelectSingleNode("password").InnerText;
    string srvr = db.SelectSingleNode("server").InnerText;
    string dbn = db.SelectSingleNode("dbname").InnerText;
    //Here a FormatException can be thrown by both these Parse()
    //And I need to know which is the caller in order to display the correct error message
    bool clean_db = ParseDbAttributeValue(db.Attributes["clean"].Value);
    bool functions = ParseDbAttributeValue(db.Attributes["insertFunctions"].Value);
    return new DatabaseConfiguration(usr, psw, srvr, dbn, clean_db, functions);
}
catch (XPathException)
{
    Console.WriteLine("<database> node is missing");
}
catch(FormatException e)
{
    //Here I'm supposed to do something to get the caller
    Console.WriteLine("Error message");
}
private bool ParseDbAttributeValue(object myValue)
{
    return Boolean.Parse(myValue);
}

Answer 2

使用TryParse怎么样。

TryParse方法与Parse方法类似，只是如果转换失败，TryPhase方法不会抛出异常。

因此，您可以简单地使用返回的布尔值检查故障

 bool clean_db;
 if(!Boolean.TryParse(db.Attributes["clean"].Value),out clean_db)
 {
    // Failled 
 }
 bool functions;
 if(!Boolean.TryParse(Boolean.Parse(db.Attributes["insertFunctions"].Value,out functions)
 {
   // Failled
 }