C#使用try-catch捕获异常的最佳实践？

Question

假设我需要运行 methodA 并且 methodA 将抛出 FormatException。

如果我写这个 block :

try
{
    methodA();
}
catch (Exception ex)
{
    methodB();
}
catch (FormatException ex)
{
    methodC();
}

它是否会运行 methodC，知道 FormatException 也是一个异常，因此将进入 methodB 的 catchblock。

还是这样写比较好:

try
{
    methodA();
}
catch (Exception ex)
{
    if(ex is FormatException)
    {
        methodC();
    } else
    {
        methodB();
    }
}

Answer 1

不，它永远不会运行 methodC，但是如果您交换 catch 的顺序，它会:

try
{
    methodA();
}
catch (FormatException ex)
{
    methodC();    
}
catch (Exception ex)
{
    methodB();
}

引用MSDN :

It is possible to use more than one specific catch clause in the same try-catch statement. In this case, the order of the catch clauses is important because the catch clauses are examined in order. Catch the more specific exceptions before the less specific ones. The compiler produces an error if you order your catch blocks so that a later block can never be reached.