Find Item in ObservableCollection without using a loop

Question

Currently i have the following syntax  list is a list containing objects with many different properties  where Title is one of them    for  int i 0  i  lt  list Count  i         if title    list i  Title             do something          How can i access the list i  Title without having to loop over my entire collection  Since my list tends to grow large this can impact the performance of my program   I am having a lot of similar syntax across my program  accessing public properties trough a for loop and by index   But im a sure there must be a better and elegant way of doing this   The find method does seem to be a option since my list contains objects

User · Answer

An observablecollection can be a List        BuchungsSatz item   BuchungsListe ToList Find x   gt  x BuchungsAuftragId    DGBuchungenAuftrag CurrentItem Id

User · Answer

Well if you have N objects and you need to get the Title of all of them you have to use a loop  If you only need the title and you really want to improve this  maybe you can make a separated array containing only the title  this would improve the performance  You need to define the amount of memory available and the amount of objects that you can handle before saying this can damage the performance  and in any case the solution would be changing the design of the program not the algorithm

User · Answer

Consider creating an index  A dictionary can do the trick  If you need the list semantics  subclass and keep the index as a private member

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i had to use it for a condition add if you don t need the index  using System Linq    use  if list Any x   gt  x Title    title      do something here     this will tell you if any variable satisfies your given condition

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Maybe this approach would solve the problem   int result   obsCollection IndexOf title     IndexOf T  Searches for the specified object and returns the zero-based index of the first occurrence within the entire Collection    Inherited from Collection   https   docs microsoft com en-us dotnet api system collections objectmodel observablecollection-1 view netframework-4 7 2 methods

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You re looking for a hash based collection  like a Dictionary or Hashset  which the ObservableCollection is not  The best solution might be to derive from a hash based collection and implement INotifyCollectionChanged which will give you the same behavior as an ObservableCollection

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ObservableCollection is a list so if you don t know the element position you have to look at each element until you find the expected one   Possible optimization If your elements are sorted use a binary search to improve performances otherwise use a Dictionary as index

User · Answer

Here comes Linq   var listItem   list Single i   gt  i Title    title     It throws an exception if there s no item matching the predicate  Alternatively  there s SingleOrDefault   If you want a collection of items matching the title  there s   var listItems   list Where i   gt  i Title     title

User · Answer

I Don t know what do you mean exactly  but technially speaking  this is not possible without a loop    May be you mean using a LINQ  like for example    list Where x  gt x Title    title    It s worth mentioning that the iteration over is not skipped  but simply wrapped into the LINQ query   Hope this helps   EDIT   In other words if you really concerned about performance  keep coding the way you already doing  Otherwise choose LINQ for more concise and clear syntax

User · Answer

I d suggest storing these in a Hashtable  You can then access an item in the collection using the key  it s a much more efficient lookup   var myObjects   new Hashtable    myObjects Add yourObject Title  yourObject       var myRetrievedObject   myObjects  TargetTitle

[c#] Find Item in ObservableCollection without using a loop

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