Filtering 2 lists in a performant way











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I have 2 lists:



newUpdates and updatesToAdd



I first of all need to remove all the occurrences of updatesToAdd from the newUpdates list by their Id. Then I need to add all updatesToAdd back into newUpdates to prevent duplicates.



It may not be clear why I'm doing this, but I need to swap out multiple occurrences of items that share the same Id (different update type) to then reinsert just one item for that Id with a main/master/catch all update type.



The code I have so far does this, but it runs very slowly. Is there a more performant way to write this?



    var newUpdates = new List<Entity>();

    var updatesToAdd = new List<Entity>();



    var Ids = updatesToAdd.Select(x => x.Id).ToList();

    newUpdates.RemoveAll(x => Ids.Contains(x.Id));

    newUpdates.AddRange(updatesToAdd);


I tried doing:



    newUpdates.Union(updatesToAdd).ToList();


However, I still ended up with duplicates in my list.






c# linq







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  • 1




    Use a HashSet for Ids. Solves both your performance and duplicates issue.
    – Funk
    Nov 22 at 17:22

















up vote
0
down vote

favorite












I have 2 lists:



newUpdates and updatesToAdd



I first of all need to remove all the occurrences of updatesToAdd from the newUpdates list by their Id. Then I need to add all updatesToAdd back into newUpdates to prevent duplicates.



It may not be clear why I'm doing this, but I need to swap out multiple occurrences of items that share the same Id (different update type) to then reinsert just one item for that Id with a main/master/catch all update type.



The code I have so far does this, but it runs very slowly. Is there a more performant way to write this?



    var newUpdates = new List<Entity>();

    var updatesToAdd = new List<Entity>();



    var Ids = updatesToAdd.Select(x => x.Id).ToList();

    newUpdates.RemoveAll(x => Ids.Contains(x.Id));

    newUpdates.AddRange(updatesToAdd);


I tried doing:



    newUpdates.Union(updatesToAdd).ToList();


However, I still ended up with duplicates in my list.






c# linq







share|improve this question




















  • 1




    Use a HashSet for Ids. Solves both your performance and duplicates issue.
    – Funk
    Nov 22 at 17:22















up vote
0
down vote

favorite









up vote
0
down vote

favorite











I have 2 lists:



newUpdates and updatesToAdd



I first of all need to remove all the occurrences of updatesToAdd from the newUpdates list by their Id. Then I need to add all updatesToAdd back into newUpdates to prevent duplicates.



It may not be clear why I'm doing this, but I need to swap out multiple occurrences of items that share the same Id (different update type) to then reinsert just one item for that Id with a main/master/catch all update type.



The code I have so far does this, but it runs very slowly. Is there a more performant way to write this?



    var newUpdates = new List<Entity>();

    var updatesToAdd = new List<Entity>();



    var Ids = updatesToAdd.Select(x => x.Id).ToList();

    newUpdates.RemoveAll(x => Ids.Contains(x.Id));

    newUpdates.AddRange(updatesToAdd);


I tried doing:



    newUpdates.Union(updatesToAdd).ToList();


However, I still ended up with duplicates in my list.






c# linq







share|improve this question















I have 2 lists:



newUpdates and updatesToAdd



I first of all need to remove all the occurrences of updatesToAdd from the newUpdates list by their Id. Then I need to add all updatesToAdd back into newUpdates to prevent duplicates.



It may not be clear why I'm doing this, but I need to swap out multiple occurrences of items that share the same Id (different update type) to then reinsert just one item for that Id with a main/master/catch all update type.



The code I have so far does this, but it runs very slowly. Is there a more performant way to write this?



    var newUpdates = new List<Entity>();

    var updatesToAdd = new List<Entity>();



    var Ids = updatesToAdd.Select(x => x.Id).ToList();

    newUpdates.RemoveAll(x => Ids.Contains(x.Id));

    newUpdates.AddRange(updatesToAdd);


I tried doing:



    newUpdates.Union(updatesToAdd).ToList();


However, I still ended up with duplicates in my list.






c# linq




c# linq






share|improve this question















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edited Nov 22 at 18:02









Uwe Keim

27.3k30128210




27.3k30128210










asked Nov 22 at 17:13









Dave

606




606








  • 1




    Use a HashSet for Ids. Solves both your performance and duplicates issue.
    – Funk
    Nov 22 at 17:22
















  • 1




    Use a HashSet for Ids. Solves both your performance and duplicates issue.
    – Funk
    Nov 22 at 17:22










1




1




Use a HashSet for Ids. Solves both your performance and duplicates issue.
– Funk
Nov 22 at 17:22






Use a HashSet for Ids. Solves both your performance and duplicates issue.
– Funk
Nov 22 at 17:22














1 Answer
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Why not use Except instead?
https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.except?view=netframework-4.7.2



or Contains is false.



In fact I think you have a bug. I think you want to do this:



var newUpdates = new List<Entity>(); //overall list to add

var updatesToAdd = new List<Entity>();  //later list to add



var Ids = updatesToAdd.Select(x => x.Id).ToList();  //this line chagned

newUpdates.RemoveAll(x => Ids.Contains(x.Id));

newUpdates.AddRange(updatesToAdd);





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    up vote
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    down vote













    Why not use Except instead?
    https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.except?view=netframework-4.7.2



    or Contains is false.



    In fact I think you have a bug. I think you want to do this:



    var newUpdates = new List<Entity>(); //overall list to add
    
var updatesToAdd = new List<Entity>();  //later list to add
    

    
var Ids = updatesToAdd.Select(x => x.Id).ToList();  //this line chagned
    
newUpdates.RemoveAll(x => Ids.Contains(x.Id));
    
newUpdates.AddRange(updatesToAdd);





    share|improve this answer



























      up vote
      1
      down vote













      Why not use Except instead?
      https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.except?view=netframework-4.7.2



      or Contains is false.



      In fact I think you have a bug. I think you want to do this:



      var newUpdates = new List<Entity>(); //overall list to add
      
var updatesToAdd = new List<Entity>();  //later list to add
      

      
var Ids = updatesToAdd.Select(x => x.Id).ToList();  //this line chagned
      
newUpdates.RemoveAll(x => Ids.Contains(x.Id));
      
newUpdates.AddRange(updatesToAdd);





      share|improve this answer

























        up vote
        1
        down vote










        up vote
        1
        down vote









        Why not use Except instead?
        https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.except?view=netframework-4.7.2



        or Contains is false.



        In fact I think you have a bug. I think you want to do this:



        var newUpdates = new List<Entity>(); //overall list to add
        
var updatesToAdd = new List<Entity>();  //later list to add
        

        
var Ids = updatesToAdd.Select(x => x.Id).ToList();  //this line chagned
        
newUpdates.RemoveAll(x => Ids.Contains(x.Id));
        
newUpdates.AddRange(updatesToAdd);





        share|improve this answer














        Why not use Except instead?
        https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.except?view=netframework-4.7.2



        or Contains is false.



        In fact I think you have a bug. I think you want to do this:



        var newUpdates = new List<Entity>(); //overall list to add
        
var updatesToAdd = new List<Entity>();  //later list to add
        

        
var Ids = updatesToAdd.Select(x => x.Id).ToList();  //this line chagned
        
newUpdates.RemoveAll(x => Ids.Contains(x.Id));
        
newUpdates.AddRange(updatesToAdd);






        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited Nov 22 at 17:33

























        answered Nov 22 at 17:24









        Jeff Davies

        458411




        458411






























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