C#:多个 catch 子句

Question

考虑以下几点:

try { 
    FileStream fileStream = new FileStream("C:\files\file1.txt", FileMode.Append); }
catch (DirectoryNotFoundException e) 
    { MessageBox.Show("Directory not found. " + e.Message); }
catch (IOException e) 
    { MessageBox.Show("Other IO Error. " + e.Message); }
catch (Exception e) 
    { MessageBox.Show("Other Error. " + e.Message); }

DirectoryNotFoundException 异常是由所有三个 catch 子句处理还是仅由第一个子句处理？

Answer 1

只是第一个。异常不会传播到所有 匹配的 catch 子句。

来自 C# 4 规范，第 8.9.5 节:

The first catch clauses that specifies the exception type or a base type of the exception type is considered a match. [...] If a matching catch clause is located, the exception propagation is completed by transferring control to the block of that catch clause.

这里的“完成”部分表示控制权转移后，特殊处理结束，有效。