Working With Multiple Tables in MVC Using Entity Framework

<connectionStrings>
    <add name="StudentCourseContext" connectionString="server=.; database=db_StudentEntity; integrated security=sspi" providerName="System.Data.SqlClient"/>
</connectionStrings>

But when we say StudentCourseContext, we don't get any IntelliSense, and if we hardcode the class name we get a compile-time error.

But we have a class with that name in our project. So, why are we getting this error? If you look at the StudentController class, it is present in the StudentEntities.Controllers namespace but if you look at the StudentCourseContext class, it is present in the StudentEntitse.Models namespace.

So, in order to use this class we need to import that namespace first.

In this StudentCourseContext class we have a property Courses and to invoke this property we can say cs. Courses.

Look at the return type of this property. It is returning us the DbSet<Course> but we want to return a list of Courses back and for that, we can convert this course property to a list using the ToList() extension method present in the System. Linq namespace.

After initializing the records in the List object, pass the object to the view.

But you might be wondering why we are able to convert the Courses property to a list since it returns a DbSet<Course> object back. Because this DbSet class implements the IEnumerable interface.

Step 12. The next step is to add a view and for that right-click on the Index method and click Add view.

The View name should be Index. The View engine should be Razor. Check, create a strongly typed view, and select Course class as a model. Select List as the scaffold template then click Add. In the Index.cshtml, you will see much auto-generated code. But don't worry about it. We will discuss it in just a bit but before let's run our application.

When we run the application, we get the preceding error stating “The resource cannot be found”. We have written our code in a simple and best possible way, so what went wrong? If you recap from the previous article of this series, we have discussed MVC is all about the convention and all the route information that is stored in routeconfig.cs states how every MVC should work. This file is present in the App_start directory. To learn more click here.

Above here, look at the default name of the controller. It is Home, but our controller name is Student. So, to override the default convention we must replace Home with Student.

If we run the application we will now get the output as expected which is all the course names.

Look at the preceding output, we have all the course names. But there is a slight problem with our Index view.

1. We don't want Create, Edit, Details and Delete hyperlinks.
2. We want all the course names as hyperlinks that when clicked will redirect to the details of the students that opted for the course that we clicked.

Remove this highlighted code.

Run the application.

Now, let's look at the code that generated the read-only text for us.

@Html.DisplayFor is nothing but a HTML helper that generates controls like TextBox, checkbox, dropdownlist and so on. But let's see which HTML helper generates a hyperlink?

The code that we removed from the Index view that created a Create hyperlink. The ActionLink HTML helper generates a hyperlink for us.

The first parameter is the link text and the second parameter is the action method name to which this Index view will be redirected to. Run the application.

Currently if we click on any of the links, we will get an exception.

It is trying to navigate to the StudentName action method but currently in our Student controller we don't have any action method with that name.

Step 13. The next step is to add a StudentName action method in the StudentController class.

We have created a new object for the StudentCourseContext class and then we invoked the Students property that contains all the student records.

But by just converting the Students property and initializing it into a list object will not give us the student records specific to a course back. It will give us all the student records, no matter what course name link we click. So, to overcome this problem, we will add a parameter in this StudentName action method and we will also add a new object routeValue in the action link we created in Index view.

In Index view

We have created a new RouteValue object Id in which we have passed the courseId. So, when we click any of the links then the courseId with that specific course name will be assigned to the course link.

We will use this same Id object and pass it in as a parameter in the StudentName action method and when we click the link in the Index view then CourseId from the action link will be passed here.

Now the next step is to filter the records based on a condition that will check if the CourseId of the Course and the course id of the student matches and if the match is found, it will display the student records. To filter a record, we can use the Where extension method present in the System.Linq namespace.

Step 14. The next step is to create a StudentName view and for that right-click on the StudentName action method and click Add view.

The View name should be StudentName. The View engine should be Razor. The Model class should be Student. The Scaffold template should be List. Click Add. Remove these codes from the StudentName view.

Run the application.

Click on the C# link.

It gave us the Student records who opted for C#. Click on ASP.Net.

Click on PHP.

Click on Java.

So, in this article we saw how easy it is to work with multiple tables in MVC. I hope you like it. Thank you.