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Sam Sam - 9 months ago 223
C# Question

Select Tag Helper in MVC 6

I need some help with the select tag helper in MVC 6.

I have a list of employees that I'm trying to bind to a select tag helper. My employees are in a

List<Employee> EmployeesList
and selected value will go into
EmployeeId
property. My view model looks like this:

public class MyViewModel

{

   public int EmployeeId { get; set; }

   public string Comments { get; set; }

   public List<Employee> EmployeesList {get; set; }

}


My employee class looks like this:

public class Employee

{

   public int Id { get; set; }

   public string FullName { get; set; }

}


My question is how do I tell my select tag helper to use the
Id
as the value while displaying
FullName
in the drop down list?

<select asp-for="EmployeeId" asp-items="???" />


I'd appreciate some help with this. Thanks.

Shyju Shyju
Answer

Using the Select Tag helpers to render a SELECT element in your view

In your GET action, create an object of your view model, load the EmployeeList collection property and send that to the view.

public IActionResult Create()
{
    var vm = new MyViewModel();
    vm.EmployeesList = new List<Employee>
    {
        new Employee {Id = 1, FullName = "Shyju"},
        new Employee {Id = 2, FullName = "Scot"}
    };
    return View(vm);
}

And in your create view, create a new SelectList object from the EmployeeList property and pass that as value for the asp-items property.

@model MyViewModel
<form asp-controller="Home" asp-action="Create">

    <select asp-for="EmployeeId" 
                    asp-items="@(new SelectList(Model.EmployeesList,"Id","FullName"))">
        <option>Please select one</option>
    </select>
    <input type="submit"/>
</form>

And your HttpPost action method to accept the submitted form data.

[HttpPost]
public IActionResult Create(MyViewModel model)
{
   //  check model.EmployeeId 
   //  to do : Save and redirect
}

Or if your view model has a List<SelectListItem> as the property for your dropdown items.

public class MyViewModel
{
    public int EmployeeId { get; set; }
    public string Comments { get; set; }
    public List<SelectListItem> Employees { set; get; }
}

And in your get action,

public IActionResult Create()
{
    var vm = new MyViewModel();
    vm.Employees = new List<SelectListItem>
    {
        new SelectListItem {Text = "Shyju", Value = "1"},
        new SelectListItem {Text = "Sean", Value = "2"}
    };
    return View(vm);
}

And in the view, you can directly use the Employees property for the asp-items.

@model MyViewModel
<form asp-controller="Home" asp-action="Create">
    <label>Comments</label>
    <input type="text" asp-for="Comments"/>

    <label>Lucky Employee</label>
    <select asp-for="EmployeeId" asp-items="@Model.Employees" >
        <option>Please select one</option>
    </select>
    <input type="submit"/>
</form>

The class SelectListItem belongs to Microsoft.AspNet.Mvc.Rendering namespace.

Multi select dropdown

If you want to render a multi select dropdown, you can simply change your view model property which you use for asp-for attribute in your view to an array type.

public class MyViewModel
{
    public int[] EmployeeIds { get; set; }
    public List<SelectListItem> Employees { set; get; }
}

This will render the HTML markup for the select element with the multiple attribute which will allow the user to select multiple options.

@model MyViewModel
<select id="EmployeeIds" multiple="multiple" name="EmployeeIds">
    <option>Please select one</option>
    <option value="1">Shyju</option>
    <option value="2">Sean</option>
</select>
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