Radio Button Tag Helpers in ASP.NET 5 MVC 6

Question

I don't see any tag helpers for radio buttons in ASP.NET 5 MVC 6. What's the right way of handling form elements where I need to use radio buttons?

Answer 1

There is a TagHelper for all the input types which includes the radio button type as well. Assuming you have a view model like this

public class CreateUserVm
{
    public string UserName { set; get; }
    public IEnumerable<RoleVm> Roles { set; get; } 
    public int SelectedRole { set; get; }
}
public class RoleVm
{
    public int Id { set; get; }
    public string RoleName { set; get; }        
}

And in your GET action,

public IActionResult Index()
{
    var vm = new CreateUserVm
    {
        Roles = new List<RoleVm>
        {
            new RoleVm {Id = 1, RoleName = "Admin"},
            new RoleVm {Id = 2, RoleName = "Editor"},
            new RoleVm {Id = 3, RoleName = "Reader"}
        }
    };
    return View(vm);
}

In the view, You can simply use markup for the input tag.

@model YourNamespaceHere.CreateUserVm
<form asp-action="Index" asp-controller="Home">
    <label class="label">User name</label>
    <div class="col-md-10">
        <input type="text" asp-for="UserName" />
    </div>
    <label class="label">Select a Role</label>
    <div class="col-md-10">
    @foreach (var item in Model.Roles)
    {
       <input asp-for="SelectedRole" type="radio" value="@item.Id" /> @item.RoleName
    }
    </div>
    <input type="submit" />
</form>

When you post your form, The Rold Id for the selected role will be in the SelectedRole property

Keep in mind that, the above razor code will generate input element with same Id attribute value and name attribute value for each input generated by the loop. In the above example, it will generate 3 input elements(radio button type) with the Id and name attribute value set to SelectedRole. Model binding will work as the name attribute value matches with the property name(SelectedRole) in our view model, but the duplicate Id attribute values might give you trouble with client side code (duplicate Ids in a document is invalid)

Answer 2

While there are solutions to use asp-for="SomeField", I found that the easiest solution was to just match a view model field with the radio button's name field.

View Model:

public class MyViewModel
{
   public string MyRadioField { get; set; }
}

Form (without labels for clarity):

@model MyViewModel
<form asp-action="SomeAction" asp-controller="SomeController">
   <input type="radio" name="MyRadioField" value="option1" checked />
   <input type="radio" name="MyRadioField" value="option2" />
   <input type="radio" name="MyRadioField" value="option3" />

   <input type="submit" />
</form>

When the form is submitted, MyRadioField is populated with value of the checked radio button.