ASP.NET MVC - ViewModel nested loop

Question

I am new to ASP.NET MVC and trying to list some companies, then all contacts under that each company. I think I am getting close to make it work, so please help if you can.

The model for table and field name:

namespace ERP.Models
{
    [Table("ERP_Company")]
    public class ERP_Company
    {
        [Key]
        public int CompanyID { get; set; }
        public string Name { get; set; }
    }

    [Table("ERP_CompanyContact")]
    public class ERP_Contact
    {
        [Key]
        public int ContactID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int CompanyID { get; set; }
    }
}

These are the methods getting the Company and Contact list:

namespace ERP.Models
{
    public class Method1
    {
        public ERPEntities db = new ERPEntities();

        public List<ERP_Company> getCompanyList()
        {
            List<ERP_Company> companyList = (
                from c in db.ERP_Company
                where c.Name.Contains("Network")
                select c).Take(10).ToList();    
            return companyList;
        }

        // This below method needs to get the passing CompanyID from getCompanyList for filtering.
        public List<ERP_Contact> getContactList()
        {
            List<ERP_Contact> contactList = (
                from cc in db.ERP_CompanyContact
                select cc).Take(50).ToList();
            return contactList;
        }

        /*  Tried this below, but not work for the Controller, maybe I am doing wrong.
        public List<ERP_Contact> getContactList(int CompanyID)
        {
            List<ERP_Contact> contactList = (
                from cc in db.ERP_CompanyContact
                where cc.CompanyID == CompanyID
                select cc).Take(50).ToList();
            return contactList;
        }
         */

    }
}

Use ViewModel (suggested from other post), combine both models:

namespace ERP.Models
{
    public class ViewModelDemoVM
    {
        public List<ERP_Company> allCompanies { get; set; }
        public List<ERP_Contact> allContacts { get; set; }
    }
}

This code in the Controller:

Method1 _repository = new Method1();
public ActionResult ViewModelDemo()
        {
            ViewModelDemoVM vm = new ViewModelDemoVM();
            vm.allCompanies = _repository.getCompanyList();
            vm.allContacts = _repository.getContactList();
            return View(vm);
        }

Lastly, the view code:

@model ERP.Models.ViewModelDemoVM 

@{
    ViewBag.Title = "ViewModelDemo";
}

<h2>ViewModelDemo</h2>

<ul>
    @foreach (var company in Model.allCompanies)
    {         
        <li>@company.CompanyID | @company.Name</li>
        <ul>       
        <!-- HERE is I want to put the filtering... foreach contact WHERE CompanyID =  Model.allCompanies.CompanyID-->
        @foreach (var contact in Model.allContacts)
        {        
            <li>@contact.ContactID | @contact.FirstName</li>                             
        }
        </ul>
    }
</ul>

How can I filter the contacts (2nd loop) based on the @company.CompanyID? Sample code would be appreciated.

Thanks in advance.

Your view model should have the nested strucuture. That means, It wil have a list of companies, each company will have a list of contacts. Populate the data in your GET action and simply read and render in the view — Shyju
– Shyju, Commented Apr 10, 2018 at 22:45
@Shyju, sorry I'm a beginner and not able to follow your suggestions. Would be great if you can provide me a sample code. thanks for the reply. — Milacay
– Milacay, Commented Apr 10, 2018 at 23:26

user9405863 · Accepted Answer · 2018-04-10 22:49:05Z

2

you can apply where clause in second loop. try below code. i hope this helps

@model ERP.Models.ViewModelDemoVM 

    @{
        ViewBag.Title = "ViewModelDemo";
    }

    <h2>ViewModelDemo</h2>

    <ul>
        @foreach (var company in Model.allCompanies)
        {         
            <li>@company.CompanyID | @company.Name</li>
            <ul>       
            <!-- HERE is I want to put the filtering... foreach contact WHERE CompanyID =  Model.allCompanies.CompanyID-->
            @foreach (var contact in Model.allContacts.Where(x=>x.CompanyId ==company.CompanyID)
            {        
                <li>@contact.ContactID | @contact.FirstName</li>                             
            }
            </ul>
        }
    </ul>

answered Apr 10, 2018 at 22:49

user9405863

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2 Comments

Milacay Over a year ago

Yes, it works perfect. Thank you so much for helping.

user9405863 Over a year ago

@Milacay glad that I'm able to help you!

Shyju · Accepted Answer · 2018-04-11 00:08:56Z

2

You should create a view model with nested structure and use that. Remember, view models are specific to the view. So build it as your view needs it.

public class CompanyVm
{
    public string Name { set; get; }
    public IEnumerable<ContactVm> Contacts { set;get;}
}
public class ContactVm
{
    public string Name { set; get; }
}
public class ViewModelDemoVM 
{
    public List<CompanyVm> Companies { set; get; }
}

Your Contact table/entity already has a foriegn key/navigational property to Company entity/table. So all you have to do is, get the companies and it's corresponding customers,map it to our view model and use it in the view.

Add a collection type to Company entity class to access it's contacts.

public class ERP_Company
{
    [Key]
    public int CompanyID { get; set; }
    public string Name { get; set; }
    public ICollection<Contact> Contacts { set; get; }
}

Now in your action method, you can get the data

public IActionResult ViewModelDemo()
{
    var vm = new ViewModelDemoVM();
    vm.Companies = db.Companies
                     .Select(a => new CompanyVm { Name = a.Name,
                                                  Contacts = a.Contacts
                                                              .Select(c => new ContactVm
                                                                     { Name = c.Name })}
                      ).ToList();
    return View(vm);
}

Now in your view, just loop through the company and for each company, loop through it's contacts

@model ViewModelDemoVM 
@foreach(var company in Model.Companies)
{
    <h3>@company.Name</h3>
    <h5>Contacts</h5>
    @foreach(var contact in company.Contacts)
    {
        <p>@contact.Name</p>    
    }
}

Some notes

Create view models as needed by view
Do not mix entity classes (used by ORM) with view models
Keep less logic/C# code in views

I used class generic class names (Contact instead ERP_Contact) and property names. When you use the above code, make the needed changes to use your existing names if needed.

answered Apr 11, 2018 at 0:08

Shyju

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6 Comments

Milacay Over a year ago

thanks a lot for taking time posting the code, really appreciated. I am trying right now, but running into two small issues: (1) I couldn't find IActionResult for name space, can I use ActionResult instead? (2) Is there a way to filter only companies with name contains 'network' like my post (maybe from URL Query String)? I have around 15K companies and 50K contacts, I am afraid it will loop through all of them which will crash the browser if I able to get it works.

Shyju Over a year ago

1. Yes you can replace ActionResult with IActionResult. 2. You can add a filter just before Select method call in the LINQ expression. db.Companies.Where(x=>x.Name.StartsWith("M").Select(

Milacay Over a year ago

I am getting this error

The entity types 'Contact' and 'ERP_Contact' cannot share table 'ERP_CompanyContact' because they are not in the same type hierarchy or do not have a valid one to one foreign key relationship

. I just checked the Contacts table, it does have foreign key CompanyID from the Primary key of the Company table. Still figuring out... thanks again for helping. I know I am learning the correct way for ViewModel nesting.

Shyju Over a year ago

Read the lat para of the answer. I used more generic class names. You may use your existing entity

Milacay Over a year ago

thank you so much for helping. I finally got it working correctly now. the error above was because I copied the "public class ERP_Contact" and renamed to the Contact you used. Somehow, it doesn't like the `[key]' in both classes.

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