Configure Many-To-Many Relationship and ListBox control in MVC and Entty Frame Work

Relationship scenario (Many to Many Relationship)

https://www.youtube.com/watch?v=nzmk1hrYYtQ

• Trainer can train on multiple Courses 
• Eg- T1 Trainer trains on C1 and C2 Courses

• Course can be handled by multiple Trainers
• Eg- C3 Course is handled by T3, T4 and T5trainers

• Many to Many Relationship requires a new table(TrainsOnCourse) for storing the collections that are selected in the list box
• Create a new Model  Trainer

• Execute the command "Add-Migration" in package manager console and update the database for adding the trainer table in the sql server database

• Build the solution and create a new model for "TrainsOnCourse" for storing the collections selected in the list box 

• Add a DBSet entity property for the TrainsOnCourse in the DBContext class

• Modify the Trainer model for adding navigational property and for saving the collection items selected in the listbox

• Build the solution and execute the "Add-Migration" command in the package manager console for adding the new table "TrainsOnCourse"
• Update the database for running the migration file in the sql server by executing the "update-database" command in package manger console

• Open the sql server and new table "TrainsOnCourse" table should be created with 2 foreign keys

• Add a new Controller "Trainer"
• Select the "Tranier.cs" model and "DNSCContext"

• Modify the Create Action method to add multiselect list values to be populated from the Course table from the database

• Add a ListBoxControl in "Create.cshtml" view page in Trainer folder

• Run the application and goto "Trainer/Create" Actionmethod by entering in the url.
• We should be able to see the ListBox with set of values

• Save the collection list items to the database
• Modify the HTTPPost create action method to save the selected items

• Modify the Edit Action method in the Trainer controller for handling Listbox control

• Open the  "Edit.cshtml" view page of trainer and add the ListBox control

• Open the HttpPost Edit Action method of the Trainer controller and perform the required operations

• Test the application with listbox values selected with Create and edit operations

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