How to Bind a List of Employees to a Select Tag Helper in ASP.NET Core MVC?

ASP.NET Core MVC Select Tag Helper: Binding Employee Lists

This guide demonstrates how to effectively bind a list of employees to a Select Tag Helper in ASP.NET Core MVC, ensuring the selected value correctly maps to the EmployeeId property.

View Model Structure:

Let's assume your view model is structured as follows:

<code class="language-csharp">public class MyViewModel
{
    public int EmployeeId { get; set; }
    public string Comments { get; set; }
    public List<Employee> EmployeesList { get; set; }
}

public class Employee
{
    public int Id { get; set; }
    public string FullName { get; set; }
}</code>

Populating the Select List:

The key is to create a SelectList object from your EmployeesList and use it within your view. Here's how you can do it in your controller action:

<code class="language-csharp">public IActionResult Create()
{
    var vm = new MyViewModel();
    vm.EmployeesList = new List<Employee>
    {
        new Employee { Id = 1, FullName = "Shyju" },
        new Employee { Id = 2, FullName = "Bryan" }
    };
    return View(vm);
}</code>

And in your view:

<code class="language-html"><select asp-for="EmployeeId" asp-items="@new SelectList(Model.EmployeesList, \"Id\", \"FullName\")"></select></code>

This concisely binds the SelectList to the EmployeeId property, displaying FullName as the option text and using Id as the value.

Pre-selecting an Employee:

To pre-select an employee, set the EmployeeId property in your view model before passing it to the view:

<code class="language-csharp">public IActionResult Create()
{
    var vm = new MyViewModel();
    vm.EmployeesList = new List<Employee> { /* ... your employees ... */ };
    vm.EmployeeId = 2; // Pre-selects Bryan
    return View(vm);
}</code>

Alternative: Using ViewBag (Less Recommended):

While possible, using ViewBag is generally less preferred due to its dynamic nature and potential for errors. Here's an example:

<code class="language-csharp">// Controller
ViewBag.Employees = new List<SelectListItem>
{
    new SelectListItem { Text = "Shyju", Value = "1" },
    new SelectListItem { Text = "Bryan", Value = "2" }
};

// View
<select asp-for="EmployeeId" asp-items="@ViewBag.Employees"></select></code>

Advanced Scenarios:

• Multiple Selection: Use an array or list type for EmployeeId in your view model to allow multiple selections.
• Grouping: Use the SelectListItem's Group property to group options within the dropdown.

Remember to consult the official Microsoft documentation on Select Tag Helpers for more advanced features and options. Using the SelectList approach directly from your model is generally cleaner and safer than using ViewBag.

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