Home > Not Working > Dictionary.containskey Not Working

Dictionary.containskey Not Working


Related 1216Add key to a dictionary in Python?1244Check if a given key already exists in a dictionary7Custom Class used as key in Dictionary but key not found1Dictionary is returning false on Hot Network Questions Term for a perfect specimen or sample Wrong way on a bike lane? In your case you could compare based on the key's name (or on any other unique property if your class is more complex). It does so using reflection, however, so performance is compromised. http://sevevb.com/not-working/dictionary-on-mac-not-working.html

How? For example, if you have 100 items, and 10 buckets, then you only need to determine which bucket an item belongs to (by using GetHashCode) and then searching within that bucket. A better mouse trap is to give the dictionary its own comparer. You need to implement IComparable or override Key.Equals or something along those lines to get it to do what you want.

C# Dictionary Containskey String Not Working

In it, you'll get: The week's top questions and answers Important community announcements Questions that need answers see an example newsletter By subscribing, you agree to the privacy policy and terms current community chat Stack Overflow Meta Stack Overflow your communities Sign up or log in to customize your list. basically the combination of sectionName and KeyIndex are a key in the dictionary –Jaylen Jan 3 '15 at 1:58 @Mike for getashcode, looks at the post I linked in

You guessed it: it then complains about the existing key because, well, it exists. I don't know what you're trying to do so i can't advise any alternate solutions to this problem but its highly unlikely that you "need" to program it having this complex Anyhow, I have implemented the Equals() and CompareTo() functions, as well as the == and != operators. C# Iequalitycomparer In it, you'll get: The week's top questions and answers Important community announcements Questions that need answers see an example newsletter By subscribing, you agree to the privacy policy and terms

Otherwise it will use the memory address to check for equality. C# Containskey Everyone beats me to it by several minutes :) –simendsjo Jun 10 '10 at 13:50 GetHashCode should return an int in the declaration ;) –Mark Seemann Jun 10 '10 They are not 100% complete and fully functional solutions equipped with error handling. http://stackoverflow.com/questions/27750832/dictionary-containskey-in-c-sharp-is-not-finding-a-key-in-the-dictionary it turned out that I needed another class that implements only the IEqualityComparer interface and that I have to pass an instance of this second class to the Dictionary constructor.

That brings the search down from 100 items to just searching 10 (which is why dictionaries are so fast). Gethashcode Implementation C# Elaborate please –Galilyou Jun 10 '10 at 14:36 @Galilyou: I think Toby's referring to the fact that ValueType.Equals by default compares structs by checking each of their fields. TSA broke a lock for which they have a master key. For example, if your equals / hashcode spans an entities Name and Id (say), then don't change those properties of the object, or you may never see that record again (even

C# Containskey

I do not quite understand your second question. http://stackoverflow.com/questions/15905595/c-sharp-dictionary-containskey-trygetvalue-not-working Can Newton's laws of motion be proved (mathematically or analytically) or they are just axioms? C# Dictionary Containskey String Not Working For example, if I had a Dictionary(MyObject, int) and MyObject has a public property (of int) called "TypeID", could I get ContainsKey(MyObject myObject) to check to see if one of the C# Override Gethashcode See other related questions - e.g. "tag:c# dictionary equals hashcode". –user166390 Nov 7 '12 at 1:44 2 You must also ensure that your GetHashCode function always returns the same value

Observed: Key not found Expected: Key found using System.Collections.Generic; class test { struct CacheKey { object Key; public CacheKey(object key) { Key = key; } } static Dictionaryhttp://sevevb.com/not-working/dictionary-in-outlook-2007-not-working.html c# .net dictionary share|improve this question edited Jun 10 '10 at 13:52 Giorgi 21.9k562101 asked Jun 10 '10 at 13:44 SkyN 3422625 add a comment| 12 Answers 12 active oldest votes Dictionary cache = new Dictionary(); The YMD class is one of my inventions, it is a class containing only the year, month, and date. How do I make an alien technology feel alien? C# Gethashcode

How to find x and y coordinates based on the given distance? notice: I need this because I create a new instance of this "key"-class and then I call ContainsKey so the comparison must not compare instances but one of the class' properties. How to find the file where a bash function is defined? Check This Out more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed

I have modified your original example to change your fields in PermissionsKey to immutable properties and added a constructor to allow you to set them once when initially created. Dictionary C# It can be done in the following way: (The implementation is quite naive, I provide it just as the starting point) public class StringArrayComparer : IEqualityComparer { public bool Equals(string[] left, up vote 15 down vote favorite I've read the MSDN documentation on how Dictionary.ContainsKey() works, but I was wondering how it actually makes the equality comparison?

public class Key { string name; public Key(string n) { name = n; } public override bool Equals(object obj) { Key k = obj as Key; if (k == null) return

We can easily provide examples of it working, but that won't surprise anyone. –Jon Skeet Apr 9 '13 at 15:09 1 Example of your code would be very useful. What does the actual path of air within a turbojet engine look like? more hot questions question feed lang-cs about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation Is the untested/empty statement true?

Take the following example Boolean found = dict.ContainsKey(new Group("group1", "test")); The found variable is false eventhough the visual studio debugger shows that a Group with the name "group1" and type "test" Is the untested/empty statement true? The default implementation is going to check references only. http://sevevb.com/not-working/dictionary-in-word-not-working.html Otherwise, Equals (which is being called by ContainsKey to find your key) defaults to ReferenceEquals, which will return false for the two objects that you use in your example since they

Wrong way on a bike lane? Despite this, the Dictionary.ContainsKey() function will always return false, even if the key exists. Diagonalizability of matrix A Align elements to the center of another element Did the GoF really thoroughly explore "Pattern Space"? share|improve this answer answered Feb 4 '10 at 6:12 Marc Gravell♦ 634k14817662236 The object is immutable, so the hash will not change.

share|improve this answer edited Nov 7 '12 at 2:53 answered Nov 7 '12 at 2:13 vossad01 3,4791750 You'd better return TypeID.GetHashCode() –2kay Nov 7 '12 at 2:40 Code: Dictionary<(Of <(TKey, TValue>)>) Constructor (IEqualityComparer<(Of <(TKey>)>)) thx @Mutant_Fruit, it was the class name (CustomComparer) that brought me on this idea ;] in connection with another class with a similar name CollectionKey). Not the answer you're looking for?

I don't paste any code because it doesn't do anything special. I didn't saw anywhere written but only implemented in some examples: http://msdn.microsoft.com/en-us/library/ms132072.aspx @monalin: I think a string would have been a better key but I wanted to learn something new ;] If you choose to participate, the online survey will be presented to you when you leave the Msdn Web site.Would you like to participate? computinglife.wordpress.com/2008/11/20/… –meziantou Sep 19 '11 at 20:20 I got why you choose to use 397 but I'm confused as to why you only multiplied the name hash code by

share|improve this answer answered Jun 10 '10 at 13:48 Arseny 5,11822448 add a comment| up vote 1 down vote you problem is that new Key("A").Equals(new Key("A"))==false. This tells the dictionary how to compare keys. Can spacecraft defend against antimatter weapons? It contains line if (typeof (IEquatable).IsAssignableFrom((Type) genericParameter1)). –Kirill Polishchuk Nov 7 '12 at 2:40 Hm, really.

share|improve this answer answered Jun 10 '10 at 13:49 AutomatedTester 17.4k33154 add a comment| up vote 0 down vote You need to override the Equals and GetHashCode methods of your Key I am not sure why int systemReq = this._mapPermissions(sectionName, keys, systemPermissions); ; int userPerm = this._mapPermissions(sectionName, keys, userPermissions); c# authentication dictionary permissions user-permissions share|improve this question asked Jan 3 '15 at How to find the file where a bash function is defined? There is an overload of the Dictionary constructor in which you can provide the specific IEqualityComparer to use.

Jun 25 '07 #2 P: n/a Jon Skeet [C# MVP] On Jun 25, 12:25 pm, "Andrus"