c# - 方法应该处理空值吗？在这种情况下的最佳实践？

Question

我在代码中有以下情况，最好的管理方式是什么，评论中包含这些情况，请推荐最佳做法。

try
{
    string errorMessage = AccountClient.GetAccount(id, out accountDetails);

    // FIRST WAY : REMOVE THIS NULL CHECK AT ALL AND LEAVE GetAccountDetails to control
    // the Null situation?
    if (accountDetails == null)
    {
        // Second Way: This way? Throw exception here?
        throw new ArgumentNullException(nameof(accountDetails));
        //Third way? break the function?
        break;
    }

    // GetAccount Details already has null control
    Subscription subscription = AccountProcessor.GetAccountDetails(accountDetails);
}
catch (Exception e)
{
    throw;
}

Answer 1

首先是构造

catch (Exception e) {
  throw; 
}

是多余的，可以消除。现在关于null。有两个案例:

• null 是一个错误值，因此应该发出信号
• null 是预期、普通 值，因此应该继续

所以你有(null 是一个错误)

string errorMessage = AccountClient.GetAccount(id, out accountDetails);

// What's wrong: it's id which doesn't correspond to any detail 
// (we expect id being s.t. AccountClient.GetAccount(id...) returns not null detail)
if (accountDetails == null) 
  throw new ArgumentException($"Incorrect id {id} which doesn't have any detail.", 
                              nameof(id));

Subscription subscription = AccountProcessor.GetAccountDetails(accountDetails);

或者(null 是预期结果)

string errorMessage = AccountClient.GetAccount(id, out accountDetails);

if (accountDetails == null)
  return null; // or any reasonable value, or just return, or create new Subscription

Subscription subscription = AccountProcessor.GetAccountDetails(accountDetails);