In this article I will explain with an example, how to populate (bind) DropDownList with Entity Framework in ASP.Net Core Razor Pages.
Note: For beginners in ASP.Net Core Razor Pages (.Net Core 7), please refer my article ASP.Net Core 7 Razor Pages: Hello World Tutorial with Sample Program example.
 
 

Database

I have made use of the following table Customers with the schema as follows.
ASP.Net Core Razor Pages: Populate DropDownList with Entity Framework
 
I have already inserted few records in the table.
ASP.Net Core Razor Pages: Populate DropDownList with Entity Framework
 
Note: You can download the database table SQL by clicking the download link below.
          Download SQL file
 
 

Model

The Model class consists of the following properties.
public class CustomerModel
{
    [Key]
    public int CustomerId { get; set; }
    public string Name { get; set; }
}
 
 

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 (.Net Core 7) and Entity Framework, please refer my ASP.Net Core 7: Simple Entity Framework Tutorial with example. It covers all the information needed for connecting and configuring Entity Framework with ASP.Net Core.
 
using Microsoft.EntityFrameworkCore;
using Razor_DropDownList_EF.Models;
 
namespace Razor_DropDownList_EF
{
    public class DBCtx : DbContext
    {
        public DBCtx(DbContextOptions<DBCtx> options) : base(options)
        {
        }
 
        public DbSet<CustomerModel> Customers { get; set; }
    }
}
 
 

Razor PageModel (Code-Behind)

The PageModel consists of following Handler methods.

Handler method for handling GET operation

Inside this Handler method, the records are fetched from the Customers table using Entity Framework and are copied to SelectList class object.
Then, it is assigned to the public property of SelectList class Customers, which is used for populating DropDownList.
 

Handler method for handling POST operation

This Handler method handles the POST call when the Submit Button is clicked and the Form is submitted.
This Handler method accepts the CustomerId and Name of the selected Customer in an HTML SELECT element (DropDownList) as parameter which ultimately set into a ViewData object.
public class IndexModel : PageModel
{
    private DBCtx Context { get; }
    public IndexModel(DBCtx _context)
    {
        this.Context = _context;
    }
 
    public SelectList Customers { get; set; }
 
    public void OnGet()
    {
        this.Customers = new SelectList(this.Context.Customers, "CustomerId", "Name");
    }
 
    public void OnPostSubmit(string customerId, string customerName)
    {
        this.Customers = new SelectList(this.Context.Customers, "CustomerId", "Name");
        string message = "Name: " + customerName;
        message += "\\nCustomer Id: " + customerId;
        ViewData["Message"] = message;
    }
}
 
 

Razor Page (HTML)

HTML Markup

The HTML of Razor Page consists of an HTML Form with an HTML SELECT element (DropDownList), a Hidden Field and a Submit Button.
The Submit Button has been set with the POST Handler method using the asp-page-handler attribute.
Note: In the Razor PageModel, the Handler method name is OnPostSubmit but here it will be specified as Submit when calling from the Razor HTML Page.
 
The Model data has been assigned to the DropDownList using the asp-items Tag Helpers attribute.
 
Inside the Razor Page, the following script file is inherited.
1. jquery.min.js
The DropDownList has been assigned with a jQuery onchange event handler which is triggered when selected item of the DropDownList is changed.
Inside this event handler, the Hidden Field is set with the Name of the selected customer.
 

Form Submitting

When the Submit Button is clicked, the ViewData object checked for NULL and if it is not NULL then the CustomerId and Name values of the selected customer is displayed using JavaScript Alert Message Box.
@page
@addTagHelper*, Microsoft.AspNetCore.Mvc.TagHelpers
@model Razor_DropDownList_EF.Pages.IndexModel
 
@{
    Layout = null;
}
 
<!DOCTYPE html>
 
<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <form method="post">
        <select id="ddlCustomers" name="CustomerId" asp-items="@Model.Customers">
            <optionvalue="0">--Select Customer--</option>
        </select>
        <input type="hidden" name="CustomerName" />
        <br />
        <br />                      
        <input type="submit" value="Submit" asp-page-handler="Submit" />       
    </form>
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
    <script type="text/javascript">
        $("body").on("change", "#ddlCustomers", function () {
            $("input[name=CustomerName]").val($(this).find("option:selected").text());
        });
    </script>
    @if (ViewData["Message"] != null)
    {
        <script type="text/javascript">
            $(function () {
                alert("@ViewData["Message"]");
             });
        </script>
    }
</body>
</html>
 
 

Screenshot

ASP.Net Core Razor Pages: Populate DropDownList with Entity Framework
 
 

Downloads

Download Code