HiveBrain v1.2.0
Get Started
← Back to all entries
snippetcsharpCritical

How can I detect if this dictionary key exists in C#?

Submitted by: @import:stackoverflow-api··
0
Viewed 0 times
keyhowdetectexistscandictionarythis

Problem

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 = "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...
}


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

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

The given key was not present in the dictionary.

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

Solution

You can use ContainsKey:

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


or TryGetValue:

dict.TryGetValue(key, out value);


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.

Example usage:

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


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();
    }
}


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

Code Snippets

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

Context

Stack Overflow Q#2829873, score: 1128

Revisions (0)

No revisions yet.