HELP: Creating an ActionResult method to display a particular database record using Entity Framework RSS

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  sam.pat

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  HELP: Creating an ActionResult method to display a particular database record using Entity Framew...

  May 17, 2011 11:01 PM|LINK

  Hi All,

  I have an ActionResult method that displays records from a database table (below):

  namespace STD.Controllers
  {
      public class StudentController: Controller
      {
          StudentEntities stud;
          
          public StudentController()
      {
          stud= new StudentEntities ();
  
      }
  
          public ActionResult Index()
          {
              ViewData.Model = stud.StudentTable.ToList();
              return View();
  
          }
  }

  I want to design a method "ActionResult Student()" that accepts "Student ID" as a parameter and displays record for that particular student only.

  What do I need to do to make this happen? Could anyone please help me with this?

  Thanks in advance

   

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  chohmann

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  Re: HELP: Creating an ActionResult method to display a particular database record using Entity Fr...

  May 18, 2011 05:19 AM|LINK

   

  namespace STD.Controllers
  {
      public class StudentController: Controller
      {
          StudentEntities stud;
          
          public StudentController()
      {
          stud= new StudentEntities ();
      }
  
          public ActionResult Index()
          {
              ViewData.Model = stud.StudentTable.ToList();
              return View();
          }
          public ActionResult Student(int id)
          {
              Student s = stud.StudentTable.Find(id);
              return View(s);
          }
  }

  Then right-click anywhere in the Student action and select "Add View". In the Add View dialog create a strongly-typed detail view on the Student class.

  Please mark as answered if this helped.
  • Edited by chohmann on May 18, 2011 05:21 AM
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  tdykstra

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  Re: HELP: Creating an ActionResult method to display a particular database record using Entity Fr...

  May 18, 2011 11:15 AM|LINK

  See the EF/MVC tutorial series at this location:

  http://asp.net/entity-framework/tutorials

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  sam.pat

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  Re: HELP: Creating an ActionResult method to display a particular database record using Entity Fr...

  May 18, 2011 04:10 PM|LINK

  Thanks for helping chohmann,

  Isnt "Student" a method? I get an error "STD.Controllers.StudentController.Student(int) is a method but used like a type, when I use it like this:

  chohmann

  public ActionResult Student(int id) { Student s = stud.StudentTable.Find(id); return View(s); }

   

  Also, I get the following error when I use the "Find" method:

  Error 205 'System.Data.Objects.ObjectQuery<STD.Models.StudentTable>' does not contain a definition for 'Find' and no extension method 'Find' accepting a first argument of type 'System.Data.Objects.ObjectQuery<STD.Models.StudentTable>' could be found (are you missing a using directive or an assembly reference?)

  Am I missing some steps before using the Student method you gave?

  <div></div>

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  chohmann

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  Re: HELP: Creating an ActionResult method to display a particular database record using Entity Fr...

  May 18, 2011 05:22 PM|LINK

  Sorry, I assumed you were using a DbContext. It sounds like your using an ObjectContext. See if this works:

  public ActionResult Student(int id)
          {
              var s = stud.StudentTable.First(s => s.Id == id);
              return View(s);
          }

  I'm assuming the id field for the student table is "Id".

  Please mark as answered if this helped.
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  sam.pat

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  Re: HELP: Creating an ActionResult method to display a particular database record using Entity Fr...

  May 18, 2011 05:55 PM|LINK

  Got it. The id field for student table is "StudentId"

  I get the following error at "var s" :

  Error 205 A local variable named 's' cannot be declared in this scope because it would give a different meaning to 's', which is already used in a 'child' scope to denote something else

  <div></div>

   

   

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  chohmann

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  Re: HELP: Creating an ActionResult method to display a particular database record using Entity Fr...

  May 18, 2011 05:59 PM|LINK

  Lol. Sorry, try this:

   

  public ActionResult Student(int id)
          {
              var s = stud.StudentTable.First(x => x.StudentId == id);
              return View(s);
          }

  I make this mistake at least once a day. You would think it would eventually sink in.

  Please mark as answered if this helped.
  • Edited by chohmann on May 18, 2011 06:01 PM
  • Edited by chohmann on May 18, 2011 06:02 PM
  • Edited by chohmann on May 18, 2011 06:03 PM
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  sam.pat

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  Re: HELP: Creating an ActionResult method to display a particular database record using Entity Fr...

  May 18, 2011 06:23 PM|LINK

  Thanks!

  But, I still get an error "Error 204 Operator '==' cannot be applied to operands of type 'string' and 'int' " <div></div>

  chohmann

  var s = stud.StudentTable.First(x => x.StudentId == id);

  When I get it to just "=" I get the error "Error 204 Cannot implicitly convert type 'int' to 'string' "

  Do I declare it a different way?

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  chohmann

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  Re: HELP: Creating an ActionResult method to display a particular database record using Entity Fr...

  May 18, 2011 06:26 PM|LINK

  Is StudentId a string? If so, try this:

  public ActionResult Student(string id)
          {
              var s = stud.StudentTable.First(x => x.StudentId == id);
              return View(s);
          }

  Please mark as answered if this helped.
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  sam.pat

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  Re: HELP: Creating an ActionResult method to display a particular database record using Entity Fr...

  May 18, 2011 06:53 PM|LINK

  Got that to work.

  Now, I did what you asked earlier: I am adding the strongly typed view, selecting the View data class (Database view: Entity Framework) and selecting "Details" from View content dropdown. This creates a Student.aspx view under Student folder in Views.

  When I start debugging, I see the entire Students Table at URL: http://localhost:12121/Students

  But, when I use URL: http://localhost:12121/Students/Student?StudentId=Jd112 I get the following error:

  Sequence contains no elements

  Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
  
  Exception Details: System.InvalidOperationException: Sequence contains no elements
  
  Source Error:

  Line 31:         public ActionResult Student(string id) Line 32:         { Line 33:             var s = stud.StudentTable.First(x => x.StudentId == id); Line 34:             Line 35:             return View(s);

  Do I need to make any changes to the Student.aspx page to display the data I want for a particular student?