How to read the data from a dropdown in ASP.Net MVC 3

Create a ViewModel for your form

public class CompanyViewModel
{
  public int CompanyId { set;get;}
  // Other properties of Company
  public int SelectedLocationId { set;get;}
  public IEnumerable<Location> Locations { set;get;}
}

Assuming you have a Location class like this

public class Location
{
  public int Id { set;get;}
  public string Name { set;get;}
}

In the Register (HTTPGET) Action method, Return a CompanyViewModel object with Locations filled from database to the View

public ActionReuslt Register()
{
  CompanyViewModel model=new CompanyViewModel();
  model.Locations =myRepositary.GetAllLocations();
  return View(model);
} 

Assuming GetAllLocations returns a list of Location objects from your repositary.

And in the Register View which is strongly typed to CompanyViewModel

@model CompanyViewModel
@using(Html.BeginForm())
{

  @Html.DropDownListFor(x=>x.SelectedLocationId,
                     new SelectList(Model.Locations ,"Id",
                     "Name"),"Select Location")

  <input type="submit" value="Save" />
}

Now write an HTTPPost actionmethod to handle the form post(when user submits the form)

[HttpPost]
public ActionResult Register(CompanyViewModel model)
{
 if(ModelState.IsValid)
 {
  // You will have selected Location id available in model.SelectedLocationId property now
  //Save and redirect.
 }
 //Model Validation failed. so Let us reload the locations again
 //because HTTP is stateless and ASP.NET MVC is true to HTTP ! :)
 model.Locations =myRepositary.GetAllLocations();
 return View(model);
}

Here is some sample code that you can modify and use in your scenario. I don't know what your code looks like so I created my own.

In your view:

@model YourProject.ViewModels.YourViewModel

Your locations dropdown:

<td><b>Location:</b></td>
<td>
     @Html.DropDownListFor(
          x => x.LocationId,
          new SelectList(Model.Locations, "Id", "Name", Model.LocationId),
          "-- Select --"
     )
     @Html.ValidationMessageFor(x => x.LocationId)
</td>

Your view model:

public class YourViewModel
{
     // Partial class

     public int LocationId { get; set; }
     public IEnumerable<Location> Locations { get; set; }
}

Your create action method:

public ActionResult Create()
{
     YourViewModel viewModel = new YourViewModel
     {
          // Get all the locations from the database
          Locations = locationService.FindAll().Where(x => x.IsActive)
     }

     // Return the view model to the view
     // Always use a view model for your data
     return View(viewModel);
}

[HttpPost]
public ActionResult Create(YourViewModel viewModel)
{
     if (!ModelState.IsValid)
     {
          viewModel.Locations = locationService.FindAll().Where(x => x.IsActive);

          return View(viewModel);
     }

     // If you browse the values of viewModel you will see that LocationId will have the
     // value (unique identifier of location) already set.  Now that you have this value
     // you can do with it whatever you like.
}

Your location class:

public class Location
{
     public int Id { get; set; }
     public string Name { get; set; }
     public bool IsActive { get; set; }
}

This is simple as can come. I hope this helps :)

UPDATE:

My service layer is there for any further business logic and then it calls my repository layer to get the data from the database. I use Entity Framework code first. I also use Autofac for my IoC container.

Your service layer:

public class LocationService : ILocationService
{
     private readonly ILocationRepository locationRepository;

     public LocationService(ILocationRepository locationRepository)
     {
          this.locationRepository = locationRepository;
     }

     public IEnumerable<Location> FindAll()
     {
          return locationRepository.FindAll();
     }
}

And your repository:

public class LocationRepository : ILocationRepository
{
     YourDbContext db = new YourDbContext();

     public IEnumerable<Location> FindAll()
     {
          return db.Locations.OrderBy(x => x.Name);
     }
}

Your database context class:

public class YourDbContext : DbContext
{
     public DbSet<Location> Locations { get; set; }
}