How can I detect if this dictionary key exists in C

Question

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

User · Answer

I use a Dictionary and because of the repetetiveness and possible missing keys, I quickly patched together a small method:

 private static string GetKey(IReadOnlyDictionary<string, string> dictValues, string keyValue)
 {
     return dictValues.ContainsKey(keyValue) ? dictValues[keyValue] : "";
 }

Calling it:

var entry = GetKey(dictList,"KeyValue1");

Gets the job done.

User · Answer

PhysicalAddressDictionary TryGetValue   public bool TryGetValue       PhysicalAddressKey key      out PhysicalAddressEntry physicalAddress

User · Answer

What is the type of c PhysicalAddresses  If it s Dictionary lt TKey TValue gt   then you can use the ContainsKey method

User · Answer

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

User · Answer

Here is a little something I cooked up today  Seems to work for me  Basically you override the Add method in your base namespace to do a check and then call the base s Add method in order to actually add it  Hope this works for you  using System  using System Collections Generic  using System Collections   namespace Main       internal partial class Dictionary lt TKey  TValue gt    System Collections Generic Dictionary lt TKey  TValue gt                internal new virtual void Add TKey key  TValue value                           if   base ContainsKey key                                 base Add key  value                                      internal partial class List lt T gt    System Collections Generic List lt T gt                internal new virtual void Add T item                        if   base Contains item                                 base Add item                                      public class Program               public static void Main                         Dictionary lt int  string gt  dic   new Dictionary lt int  string gt                 dic Add 1  b                dic Add 1  a                dic Add 2  c                dic Add 1   b                dic Add 1   a                dic Add 2   c                 string val                   dic TryGetValue 1  out val                Console WriteLine val               Console WriteLine dic Count ToString                   List lt string gt  lst   new List lt string gt                 lst Add  b                lst Add  a                lst Add  c                lst Add  b                lst Add  a                lst Add  c                 Console WriteLine lst 2                Console WriteLine lst Count ToString

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

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