如何知道是什么对象抛出了异常？

Question

try{
  return A[key1].Keys.Union(B[key1].Keys).ToList();
}
catch(KeyNotFoundException ex)
{}

任务是从 A[key1] 和 B[key1] 中找到所有的键并 "unite" 它们。但是 A[key1] 和 B[key1] 可以抛出异常，我想知道我怎么知道是 A 对象还是 B 对象抛出了这些异常？

Answer 1

使用您发布的代码块，这是不可能的。但是，您可以尝试先获取它们的值或检查它们是否存在：

if(!A.ContainsKey(key1)) // A didn't have key1
  return null; // Maybe throw exception?
if(!B.ContainsKey(key1)) // B didn't have key1
  return null; // Maybe throw a different exception?
return A[key1].Keys.Union(B[key1].Keys).ToList();

或者稍微快一点的（因为他们的键已经被搜索过了）

type a, b; // Type must be the type that A[key1] and B[key1] contains
if(!A.TryGetValue(key1, out a)) // A didn't have key1
  return null; // Maybe throw exception?
if(!B.TryGetValue(key1, out b)) // B didn't have key1
  return null; // Maybe throw a different exception?
return a.Keys.Union(b.Keys).ToList();

如何知道是什么对象抛出了异常？

How to know what object threw an exception?

c#

exception-handling

exception