c# - 如何检测此字典键是否存在于 C# 中？

Question

我正在使用 Exchange Web Services Managed API 和联系人数据。我有以下代码，它功能，但并不理想:

foreach (Contact c in contactList)
{
    string openItemUrl = "https://" + 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...
}

正如我所说，这段代码有效。现在，如果可能的话，我想让它少一点。

我找不到任何方法可以让我在尝试访问字典之前检查字典中是否存在该键，如果我尝试读取它(使用 .ToString() ) 并且它不存在则抛出异常:

500
The given key was not present in the dictionary.

我怎样才能重构这段代码以减少(同时仍然起作用)？

Answer 1

您可以使用 ContainsKey :

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

或TryGetValue :

dict.TryGetValue(key, out value);

---

更新:根据评论，这里的实际类不是IDictionary，而是PhysicalAddressDictionary。 , 所以方法是 Contains和 TryGetValue但它们的工作方式相同。

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)

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

...根据需要为每个所需的键重复内部条件。 TryGetValue 仅针对每个 PhysicalAddressKey(家庭、工作等)执行一次。