In this article I will explain with an example, how to set ListBox selected value from SQL Server database in ASP.Net Core MVC.
Note: For beginners in ASP.Net Core (.Net Core 7), please refer my article ASP.Net Core 7: Hello World Tutorial with Sample Program example.
 
 

Database

I have made use of the following table Hobbies with the schema as follow.
ASP.Net Core: Set ListBox selected value from Database
 
I have already inserted few records in the table.
ASP.Net Core: Set ListBox selected value from Database
 
Note: You can download the database table SQL by clicking the download link below.
          Download SQL file
 
 

Database Context

Once the Entity Framework is configured and connected to the database table, the Database Context will look as shown below.
Note: For beginners in ASP.Net Core and Entity Framework, please refer my article ASP.Net Core 7: Simple Entity Framework Tutorial with example. It covers all the information needed for connecting and configuring Entity Framework.
 
using Microsoft.EntityFrameworkCore;
 
namespace ListBox_Selected_DB_Core
{
    public class DBCtx : DbContext
    {
        public DBCtx(DbContextOptions<DBCtx> options) : base(options)
        {
        }
 
        public DbSet<HobbyModel> Hobbies { get; set; }
    }
}
 
 

Model

You will need to import the following namespaces.
public class HobbyModel
{
    [Key]
    public int HobbyId { get; set; }
    public string Hobby { get; set; }
    public bool IsSelected { get; set; }
}
 
 

Controller

The Controller consists of following Action method.

Action Method for handling GET operation

Inside this Action method, first the connection is read from the ConnectionStrings section of the AppSettings.json file.
Note: For more details on how to read Connection String from AppSettings.json, please refer my article .Net Core 7: Read Connection String from AppSettings.json file.
 
Then, the records are fetched from the Hobbies Table using Entity Framework and set to the respective properties of SelectListItem class object.
Finally, the Generic List collection of SelectListItem class object is returned to the View.
public class HomeController : Controller
{
    private DBCtx Context { get; }
    public HomeController(DBCtx _context)
    {
        this.Context = _context;
    }
 
    public IActionResult Index()
    {
        List<SelectListItem> hobbies = (from hobby in this.Context.Hobbies
                                        select new SelectListItem
                                        {
                                            // Set the Text.
                                            Text = hobby.Hobby,
                                            // Set the Value.
                                            Value = hobby.HobbyId.ToString(),
                                            // Set the Selected value.
                                            Selected = Convert.ToBoolean(hobby.IsSelected)
                                        }).ToList();
        return View(hobbies);
    }
}
 
 

View

HTML Markup

Inside the View, first the Generic List collection of SelectListItem class is declared as Model and the ASP.Net TagHelpers is inherited.
The View consists of an HTML SELECT (ListBox) element to which the TagHelper attribute i.e. asp-items is set to Model and multiple property is set to multiple.
@model List<SelectListItem>
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
@{
    Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    Hobbies:
    <br />
    <select id="lstHobbies" asp-items="Model" multiple="multiple"></select>
</body>
</html>
 
 

Screenshot

ASP.Net Core: Set ListBox selected value from Database
 
 

Demo

View Demo
 
 

Downloads

Download Code