Question

I have a database which has three tables: A, B, and C.

I want the view to render the data in a particular way. Looping through A, then listing rows of B under A where B.aID = A.ID, listing each row of C under each row of B where C.bId = B.ID.

I’m new to ASP.NET MVC3 and I’m not sure how to accomplish this. All the examples I’ve seen are straight forward.

Answer 1

I would start with adding three models: A, B and C. In these models, A contains a List of B’s and B contains a List of C’s. For testing purposes, I would also add something to uniquely identify them, such as a Name. Example:

public class A
{
    public string Name { get; set; }

    public List<B> Bs { get; set; }
}

public class B
{
    public string Name { get; set; }

    public List<C> Cs { get; set; }
}

public class C
{
    public string Name { get; set; }
}

In my controller, I would add an action method that fills these models with data. For testing purposes, I’m using dummy data.

public ActionResult List()
{
    C c1 = new C() { Name = "C1" };
    C c2 = new C() { Name = "C2" };
    C c3 = new C() { Name = "C3" };
    C c4 = new C() { Name = "C4" };

    B b1 = new B() { Name = "B1", Cs = new List<C>() { c1, c3 } };
    B b2 = new B() { Name = "B2", Cs = new List<C>() { c2, c4 } };
    B b3 = new B() { Name = "B3", Cs = new List<C>() { c1, c2, c4 } };
    B b4 = new B() { Name = "B4", Cs = new List<C>() { c1, c2, c3, c4 } };

    A a1 = new A() { Name = "A1", Bs = new List<B>() { b1, b2 } };
    A a2 = new A() { Name = "A2", Bs = new List<B>() { b3, b4 } };
    A a3 = new A() { Name = "A3", Bs = new List<B>() { b1, b2, b3, b4 } };

    List<A> listOfAs = new List<A>() { a1, a2, a3 };
    return View(listOfAs);
}

And for the final piece, the view to display all of this. Simply using @foreach in a nested manner gives us what we need:

@model IEnumerable<HelloMvc.Models.A>

<h2>List of As</h2>

<table>
    <tr>
        <th></th>
    </tr>

@foreach (var a in Model) {
    <tr>
        <td>
            @a.Name<br />
            @foreach (var b in a.Bs) { 
                @b.Name<br />

                foreach (var c in b.Cs)
                { 
                            @c.Name<br />
                }
            }

        </td>
    </tr>
}

Note that the “HelloMvc” is my namespace. You probably need to change this to your own namespace.

Everything put together, this results in a list of A’s with nested B’s and C’s:

A1
B1
C1
C3
B2
C2
C4
A2
B3
C1
C2
C4
B4
C1
C2
C3
C4
A3
B1
C1
C3
B2
C2
C4
B3
C1
C2
C4
B4
C1
C2
C3
C4

(You’ll have to imagine some styling.) Hope this example helps you.

(sidenote)
Funny how that third foreach doesn’t have a ‘@’ in front of it. It’s not a typo or an error, if I put it there, an exception is raised. Small bug in the Razor view engine, I suspect.