create a dictionary of list from an array of pocos?












-2















Want to create a dictionary<string, list<string>>



from a result set that has a list of:



class catalog{

public string Name { get; set; }

public string CategoryName { get; set; }

public  bool CategoryDeleted { get; set; }

}


I want the key to be the CategoryName and the value to be a List of Names.



Each Categories can have the same Name associated with it. One categoryname to many reportnames and it looks like this.



{Name = "rp1", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp2", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp3", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp1", CategoryName=cat2, CategoryDeleted = 0 }

{Name = "rp2", CategoryName=cat2, CategoryDeleted = 0 }


I'd like a clean linq query that does this concisely.



what I have so far:



var dic = new Dictionary<string, List<string>>();

catalog.Select(x => x.CategoryName).Distinct().ToList().ForEach(x =>

{

     dic.Add(x, catalog.Where(t => t.CategoryName == x).Select(t => t.ReportName).ToList());

});


I want to know if I can improve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.



thanks!






c# linq dictionary







share|improve this question

























  • I want to know if I can imporve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.

    – melmack
    Nov 21 '18 at 22:18











  • Also note you're not iterating it twice, you're iterating it once plus once more for each category.

    – Servy
    Nov 21 '18 at 22:21











  • right. added now.

    – melmack
    Nov 21 '18 at 22:21






  • 2





    Use GroupBy followed by ToDictionary.

    – Nikola Markovinović
    Nov 21 '18 at 22:23






  • 1





    Don't you rather need a lookup? items.ToLookup(c => c.CategoryName, c => c.Name)

    – Antonín Lejsek
    Nov 22 '18 at 2:17
















-2















Want to create a dictionary<string, list<string>>



from a result set that has a list of:



class catalog{

public string Name { get; set; }

public string CategoryName { get; set; }

public  bool CategoryDeleted { get; set; }

}


I want the key to be the CategoryName and the value to be a List of Names.



Each Categories can have the same Name associated with it. One categoryname to many reportnames and it looks like this.



{Name = "rp1", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp2", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp3", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp1", CategoryName=cat2, CategoryDeleted = 0 }

{Name = "rp2", CategoryName=cat2, CategoryDeleted = 0 }


I'd like a clean linq query that does this concisely.



what I have so far:



var dic = new Dictionary<string, List<string>>();

catalog.Select(x => x.CategoryName).Distinct().ToList().ForEach(x =>

{

     dic.Add(x, catalog.Where(t => t.CategoryName == x).Select(t => t.ReportName).ToList());

});


I want to know if I can improve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.



thanks!






c# linq dictionary







share|improve this question

























  • I want to know if I can imporve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.

    – melmack
    Nov 21 '18 at 22:18











  • Also note you're not iterating it twice, you're iterating it once plus once more for each category.

    – Servy
    Nov 21 '18 at 22:21











  • right. added now.

    – melmack
    Nov 21 '18 at 22:21






  • 2





    Use GroupBy followed by ToDictionary.

    – Nikola Markovinović
    Nov 21 '18 at 22:23






  • 1





    Don't you rather need a lookup? items.ToLookup(c => c.CategoryName, c => c.Name)

    – Antonín Lejsek
    Nov 22 '18 at 2:17














-2












-2








-2








Want to create a dictionary<string, list<string>>



from a result set that has a list of:



class catalog{

public string Name { get; set; }

public string CategoryName { get; set; }

public  bool CategoryDeleted { get; set; }

}


I want the key to be the CategoryName and the value to be a List of Names.



Each Categories can have the same Name associated with it. One categoryname to many reportnames and it looks like this.



{Name = "rp1", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp2", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp3", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp1", CategoryName=cat2, CategoryDeleted = 0 }

{Name = "rp2", CategoryName=cat2, CategoryDeleted = 0 }


I'd like a clean linq query that does this concisely.



what I have so far:



var dic = new Dictionary<string, List<string>>();

catalog.Select(x => x.CategoryName).Distinct().ToList().ForEach(x =>

{

     dic.Add(x, catalog.Where(t => t.CategoryName == x).Select(t => t.ReportName).ToList());

});


I want to know if I can improve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.



thanks!






c# linq dictionary







share|improve this question
















Want to create a dictionary<string, list<string>>



from a result set that has a list of:



class catalog{

public string Name { get; set; }

public string CategoryName { get; set; }

public  bool CategoryDeleted { get; set; }

}


I want the key to be the CategoryName and the value to be a List of Names.



Each Categories can have the same Name associated with it. One categoryname to many reportnames and it looks like this.



{Name = "rp1", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp2", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp3", CategoryName=cat1, CategoryDeleted = 0 }

{Name = "rp1", CategoryName=cat2, CategoryDeleted = 0 }

{Name = "rp2", CategoryName=cat2, CategoryDeleted = 0 }


I'd like a clean linq query that does this concisely.



what I have so far:



var dic = new Dictionary<string, List<string>>();

catalog.Select(x => x.CategoryName).Distinct().ToList().ForEach(x =>

{

     dic.Add(x, catalog.Where(t => t.CategoryName == x).Select(t => t.ReportName).ToList());

});


I want to know if I can improve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.



thanks!






c# linq dictionary




c# linq dictionary






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 21 '18 at 22:20







melmack

















asked Nov 21 '18 at 22:13









melmackmelmack

406




406













  • I want to know if I can imporve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.

    – melmack
    Nov 21 '18 at 22:18











  • Also note you're not iterating it twice, you're iterating it once plus once more for each category.

    – Servy
    Nov 21 '18 at 22:21











  • right. added now.

    – melmack
    Nov 21 '18 at 22:21






  • 2





    Use GroupBy followed by ToDictionary.

    – Nikola Markovinović
    Nov 21 '18 at 22:23






  • 1





    Don't you rather need a lookup? items.ToLookup(c => c.CategoryName, c => c.Name)

    – Antonín Lejsek
    Nov 22 '18 at 2:17



















  • I want to know if I can imporve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.

    – melmack
    Nov 21 '18 at 22:18











  • Also note you're not iterating it twice, you're iterating it once plus once more for each category.

    – Servy
    Nov 21 '18 at 22:21











  • right. added now.

    – melmack
    Nov 21 '18 at 22:21






  • 2





    Use GroupBy followed by ToDictionary.

    – Nikola Markovinović
    Nov 21 '18 at 22:23






  • 1





    Don't you rather need a lookup? items.ToLookup(c => c.CategoryName, c => c.Name)

    – Antonín Lejsek
    Nov 22 '18 at 2:17

















I want to know if I can imporve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.

– melmack
Nov 21 '18 at 22:18





I want to know if I can imporve my query to not have to reference the catalog list twice. once to iterate and select my keys, then another to initialize the value when I make a dictionary add.

– melmack
Nov 21 '18 at 22:18













Also note you're not iterating it twice, you're iterating it once plus once more for each category.

– Servy
Nov 21 '18 at 22:21





Also note you're not iterating it twice, you're iterating it once plus once more for each category.

– Servy
Nov 21 '18 at 22:21













right. added now.

– melmack
Nov 21 '18 at 22:21





right. added now.

– melmack
Nov 21 '18 at 22:21




2




2





Use GroupBy followed by ToDictionary.

– Nikola Markovinović
Nov 21 '18 at 22:23





Use GroupBy followed by ToDictionary.

– Nikola Markovinović
Nov 21 '18 at 22:23




1




1





Don't you rather need a lookup? items.ToLookup(c => c.CategoryName, c => c.Name)

– Antonín Lejsek
Nov 22 '18 at 2:17





Don't you rather need a lookup? items.ToLookup(c => c.CategoryName, c => c.Name)

– Antonín Lejsek
Nov 22 '18 at 2:17












2 Answers
2






active

oldest

votes


















2














Here is one more compact solution.



Dictionary<string, List<string>> dictionary = catalogs

            .GroupBy(catalog => catalog.CategoryName, catalog => catalog.Name)

            .ToDictionary(grouping => grouping.Key, grouping => grouping.ToList());





share|improve this answer































    2














    You need to use grouping:



    var dict = items.GroupBy(c => c.CategoryName).ToDictionary(g => g.Key, g => g.Select(c => c.Name));





    share|improve this answer























      Your Answer






      StackExchange.ifUsing("editor", function () {
      StackExchange.using("externalEditor", function () {
      StackExchange.using("snippets", function () {
      StackExchange.snippets.init();
      });
      });
      }, "code-snippets");

      StackExchange.ready(function() {
      var channelOptions = {
      tags: "".split(" "),
      id: "1"
      };
      initTagRenderer("".split(" "), "".split(" "), channelOptions);

      StackExchange.using("externalEditor", function() {
      // Have to fire editor after snippets, if snippets enabled
      if (StackExchange.settings.snippets.snippetsEnabled) {
      StackExchange.using("snippets", function() {
      createEditor();
      });
      }
      else {
      createEditor();
      }
      });

      function createEditor() {
      StackExchange.prepareEditor({
      heartbeatType: 'answer',
      autoActivateHeartbeat: false,
      convertImagesToLinks: true,
      noModals: true,
      showLowRepImageUploadWarning: true,
      reputationToPostImages: 10,
      bindNavPrevention: true,
      postfix: "",
      imageUploader: {
      brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
      contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
      allowUrls: true
      },
      onDemand: true,
      discardSelector: ".discard-answer"
      ,immediatelyShowMarkdownHelp:true
      });


      }
      });














      draft saved

      draft discarded


















      StackExchange.ready(
      function () {
      StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53421175%2fcreate-a-dictionary-of-liststring-from-an-array-of-pocos%23new-answer', 'question_page');
      }
      );

      Post as a guest















      Required, but never shown

























      2 Answers
      2






      active

      oldest

      votes








      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      2














      Here is one more compact solution.



      Dictionary<string, List<string>> dictionary = catalogs
      
            .GroupBy(catalog => catalog.CategoryName, catalog => catalog.Name)
      
            .ToDictionary(grouping => grouping.Key, grouping => grouping.ToList());





      share|improve this answer




























        2














        Here is one more compact solution.



        Dictionary<string, List<string>> dictionary = catalogs
        
            .GroupBy(catalog => catalog.CategoryName, catalog => catalog.Name)
        
            .ToDictionary(grouping => grouping.Key, grouping => grouping.ToList());





        share|improve this answer


























          2












          2








          2







          Here is one more compact solution.



          Dictionary<string, List<string>> dictionary = catalogs
          
            .GroupBy(catalog => catalog.CategoryName, catalog => catalog.Name)
          
            .ToDictionary(grouping => grouping.Key, grouping => grouping.ToList());





          share|improve this answer













          Here is one more compact solution.



          Dictionary<string, List<string>> dictionary = catalogs
          
            .GroupBy(catalog => catalog.CategoryName, catalog => catalog.Name)
          
            .ToDictionary(grouping => grouping.Key, grouping => grouping.ToList());






          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Nov 21 '18 at 22:27









          AlesDAlesD

          2,53829




          2,53829

























              2














              You need to use grouping:



              var dict = items.GroupBy(c => c.CategoryName).ToDictionary(g => g.Key, g => g.Select(c => c.Name));





              share|improve this answer




























                2














                You need to use grouping:



                var dict = items.GroupBy(c => c.CategoryName).ToDictionary(g => g.Key, g => g.Select(c => c.Name));





                share|improve this answer


























                  2












                  2








                  2







                  You need to use grouping:



                  var dict = items.GroupBy(c => c.CategoryName).ToDictionary(g => g.Key, g => g.Select(c => c.Name));





                  share|improve this answer













                  You need to use grouping:



                  var dict = items.GroupBy(c => c.CategoryName).ToDictionary(g => g.Key, g => g.Select(c => c.Name));






                  share|improve this answer












                  share|improve this answer



                  share|improve this answer










                  answered Nov 21 '18 at 22:29









                  KrzysztofKrzysztof

                  244215




                  244215






























                      draft saved

                      draft discarded




















































                      Thanks for contributing an answer to Stack Overflow!


                      • Please be sure to answer the question. Provide details and share your research!

                      But avoid …



                      • Asking for help, clarification, or responding to other answers.

                      • Making statements based on opinion; back them up with references or personal experience.


                      To learn more, see our tips on writing great answers.




                      draft saved


                      draft discarded














                      StackExchange.ready(
                      function () {
                      StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53421175%2fcreate-a-dictionary-of-liststring-from-an-array-of-pocos%23new-answer', 'question_page');
                      }
                      );

                      Post as a guest















                      Required, but never shown





















































                      Required, but never shown














                      Required, but never shown












                      Required, but never shown







                      Required, but never shown

































                      Required, but never shown














                      Required, but never shown












                      Required, but never shown







                      Required, but never shown







                      -

                      Popular posts from this blog

                      Create new schema in PostgreSQL using DBeaver

                      Image
                      0 At the beginning of my current job I had limited access to DB but recently my role is changed to superuser, admin, and owner. My colleague who was the previous DB admin is able to create a schema or change the permissions as there is a permission tab in the properties and he can change permissions by clicking easily. Would you please let me know how I can create schema and change permissions as well? Why his dbeaver looks different from me? He can easily right click on the schema folder on top of all schemas on the left side column and select create new schema while I do not have that, like the following picture I found on the internet. postgresql database-schema dbeaver share | improve this question
                      Read more

                      Deepest pit of an array with Javascript: test on Codility

                      Image
                      0 $begingroup$ This is the question from a Codility test, as a task in an interview: DeepestPit - problem description A non-empty zero-indexed array A consisting of N integers is given. A pit in this array is any triplet of integers (P, Q, R) such that: ·         0 ≤ P < Q < R < N; ·         sequence [A[P], A[P+1], ..., A[Q]] is strictly decreasing, i.e. A[P] > A[P+1] > ... > A[Q]; ·         sequence A[Q], A[Q+1], ..., A[R] is strictly increasing, i.e. A[Q] < A[Q+1] < ... < A[R]. The depth of a pit (P, Q, R) is the number min {A[P] − A[Q], A[R] − A[Q]}. For example, consider array A consisting of 10 elements such that: A[0] = 0 A[1] = 1 A[2] = 3 A[3] = -2 A[4] = 0 A[5] = 1 A[6] = 0 A[7] = -3 A[8] = 2 A[9] = 3 Triplet (2, 3, 4) is
                      Read more

                      Costa Masnaga

                      Image
                      .mw-parser-output .avviso .mbox-text-div>div,.mw-parser-output .avviso .mbox-text-full-div>div{font-size:90%}.mw-parser-output .avviso .mbox-image div{width:52px}.mw-parser-output .avviso .mbox-text-full-div .hide-when-compact{display:block} Questa voce o sezione sull'argomento Lombardia non cita le fonti necessarie o quelle presenti sono insufficienti . Puoi migliorare questa voce aggiungendo citazioni da fonti attendibili secondo le linee guida sull'uso delle fonti. Segui i suggerimenti del progetto di riferimento. Costa Masnaga comune Localizzazione Stato   Italia Regione Lombardia Provincia Lecco Amministrazione Sindaco Sabina Panzeri (Al centro il cittadino) dall'08/06/2009 Territorio Coordinate 45°46′N 9°17′E  /  45.766667°N 9.283333°E 45.766667; 9.283333  ( Costa Masnaga ) Coordinate: 45°46′N 9°17′E  /  45.766667°N 9.283333°E 45.766667; 9.283333  ( Costa Masnaga ) Altitudine 318 m s.l.m
                      Read more