如何检测C＃中是否存在此字典键？

本文介绍了如何检测C＃中是否存在此字典键？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在使用带有联系数据的Exchange Web服务托管API。我有以下代码，它们是功能，但不理想：

I am working with the Exchange Web Services Managed API, with contact data. I have the following code, which is functional, but not ideal:

foreach (Contact c in contactList) { string openItemUrl = "" + service.Url.Host + "/owa/" + c.WebClientReadFormQueryString; row = table.NewRow(); row["FileAs"] = c.FileAs; row["GivenName"] = c.GivenName; row["Surname"] = c.Surname; row["CompanyName"] = c.CompanyName; row["Link"] = openItemUrl; //home address try { row["HomeStreet"] = c.PhysicalAddresses[PhysicalAddressKey.Home].Street.ToString(); } catch (Exception e) { } try { row["HomeCity"] = c.PhysicalAddresses[PhysicalAddressKey.Home].City.ToString(); } catch (Exception e) { } try { row["HomeState"] = c.PhysicalAddresses[PhysicalAddressKey.Home].State.ToString(); } catch (Exception e) { } try { row["HomeZip"] = c.PhysicalAddresses[PhysicalAddressKey.Home].PostalCode.ToString(); } catch (Exception e) { } try { row["HomeCountry"] = c.PhysicalAddresses[PhysicalAddressKey.Home].CountryOrRegion.ToString(); } catch (Exception e) { } //and so on for all kinds of other contact-related fields... }

我说过，这段代码有效。现在，如果可能的话，我想让它吸一些 。

As I said, this code works. Now I want to make it suck a little less, if possible.

我找不到任何方法可以检查在尝试访问它之前，字典中是否存在该键，如果我尝试读取它（使用 .ToString（）），但它不存在，则出现异常抛出：

I can't find any methods that allow me to check for the existence of the key in the dictionary before attempting to access it, and if I try to read it (with .ToString()) and it doesn't exist then an exception is thrown:

500 字典中没有给定的键。

500 The given key was not present in the dictionary.

我该如何重构此代码以减少吸吮（同时仍然起作用）？

How can I refactor this code to suck less (while still being functional)?

推荐答案

您可以使用 ContainsKey ：

You can use ContainsKey:

if (dict.ContainsKey(key)) { ... }

或 TryGetValue ：

dict.TryGetValue(key, out value);

更新：根据发表评论，这里的实际课程不是 IDictionary ，而是 PhysicalAddressDictionary ，因此方法为 包含 和 TryGetValue ，但是它们的工作方式相同。

Update: according to a comment the actual class here is not an IDictionary but a PhysicalAddressDictionary, so the methods are Contains and TryGetValue but they work in the same way.

示例用法：

PhysicalAddressEntry entry; PhysicalAddressKey key = c.PhysicalAddresses[PhysicalAddressKey.Home].Street; if (c.PhysicalAddresses.TryGetValue(key, out entry)) { row["HomeStreet"] = entry; }

更新2 ：这是工作代码（由提问者编译）

Update 2: here is the working code (compiled by question asker)

PhysicalAddressEntry entry; PhysicalAddressKey key = PhysicalAddressKey.Home; if (c.PhysicalAddresses.TryGetValue(key, out entry)) { if (entry.Street != null) { row["HomeStreet"] = entry.Street.ToString(); } }

...根据需要重复内部条件每个所需的密钥。对于每个PhysicalAddressKey（家庭，工作等），只完成一次TryGetValue。

...with the inner conditional repeated as necessary for each key required. The TryGetValue is only done once per PhysicalAddressKey (Home, Work, etc).