Getting Started with Dropdown List

29 Jan 20249 minutes to read

Overview

The Blazor Dropdown List is a dynamic replacement of HTML select tags. It has a rich appearance and allows you to select a single value that is non-editable from a list of predefined values. It has several out-of-the-box features such as data binding, filtering, grouping, UI customization, accessibility, and preselected values.

This section briefly explains about how to include Blazor DropDown List component in your Blazor Server App and Blazor WebAssembly App using Visual Studio.

To get start quickly with Blazor DropDownList component, you can check on this video or GitHub sample.

Prerequisites

Create a new Blazor App in Visual Studio

You can create a Blazor Server App or Blazor WebAssembly App using Visual Studio via Microsoft Templates or the Syncfusion Blazor Extension.

Install Syncfusion Blazor DropDowns and Themes NuGet in the App

To add Blazor DropDown List component in the app, open the NuGet package manager in Visual Studio (Tools → NuGet Package Manager → Manage NuGet Packages for Solution), search and install Syncfusion.Blazor.DropDowns and Syncfusion.Blazor.Themes. Alternatively, you can utilize the following package manager command to achieve the same.

Install-Package Syncfusion.Blazor.DropDowns -Version 25.2.3
Install-Package Syncfusion.Blazor.Themes -Version 25.2.3

NOTE

Syncfusion Blazor components are available in nuget.org. Refer to NuGet packages topic for available NuGet packages list with component details.

Register Syncfusion Blazor Service

Open ~/_Imports.razor file and import the Syncfusion.Blazor and Syncfusion.Blazor.DropDowns namespace.

@using Syncfusion.Blazor
@using Syncfusion.Blazor.DropDowns

Now, register the Syncfusion Blazor Service in the ~/Program.cs file of your Blazor Server App or Blazor WebAssembly App.

using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Web;
using Syncfusion.Blazor;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();
builder.Services.AddSyncfusionBlazor();

var app = builder.Build();
....
using Microsoft.AspNetCore.Components.Web;
using Microsoft.AspNetCore.Components.WebAssembly.Hosting;
using Syncfusion.Blazor;

var builder = WebAssemblyHostBuilder.CreateDefault(args);
builder.RootComponents.Add<App>("#app");
builder.RootComponents.Add<HeadOutlet>("head::after");

builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });

builder.Services.AddSyncfusionBlazor();
await builder.Build().RunAsync();
....

Add stylesheet and script resources

The theme stylesheet and script can be accessed from NuGet through Static Web Assets. Reference the stylesheet and script in the <head> of the main page as follows:

  • For .NET 6 Blazor Server app, include it in ~/Pages/_Layout.cshtml file.

  • For .NET 7 Blazor Server app, include it in the ~/Pages/_Host.cshtml file.

  • For Blazor WebAssembly app, include it in the ~/index.html file.

<head>
    ....
    <link href="_content/Syncfusion.Blazor.Themes/bootstrap5.css" rel="stylesheet" />
    <script src="_content/Syncfusion.Blazor.Core/scripts/syncfusion-blazor.min.js" type="text/javascript"></script>
</head>

NOTE

Check out the Blazor Themes topic to discover various methods (Static Web Assets, CDN, and CRG) for referencing themes in your Blazor application. Also, check out the Adding Script Reference topic to learn different approaches for adding script references in your Blazor application.

Add Blazor DropDown List component

Add the Syncfusion Blazor DropDown List component in the ~/Pages/Index.razor file.

<SfDropDownList TValue="string" TItem="string" Placeholder="Select a game"></SfDropDownList>
  • Press Ctrl+F5 (Windows) or +F5 (macOS) to launch the application. This will render the Syncfusion Blazor DropDown List component in your default web browser.
Blazor DropDownList Component

Binding data source

After initialization, populate the DropDownList with data using the DataSource property.

<SfDropDownList TValue="string" TItem="Games" Placeholder="Select a game" DataSource="@LocalData">
  <DropDownListFieldSettings Value="ID" Text="Text"></DropDownListFieldSettings>
</SfDropDownList>

@code {
  public class Games
  {
    public string ID { get; set; }
    public string Text { get; set; }
  }
  List<Games> LocalData = new List<Games> {
    new Games() { ID= "Game1", Text= "American Football" },
    new Games() { ID= "Game2", Text= "Badminton" },
    new Games() { ID= "Game3", Text= "Basketball" },
    new Games() { ID= "Game4", Text= "Cricket" },
    new Games() { ID= "Game5", Text= "Football" },
    new Games() { ID= "Game6", Text= "Golf" },
    new Games() { ID= "Game7", Text= "Hockey" },
    new Games() { ID= "Game8", Text= "Rugby"},
    new Games() { ID= "Game9", Text= "Snooker" },
    new Games() { ID= "Game10", Text= "Tennis"},
  };
}
Data Binding in Blazor DropDownList

Configure the popup list

By default, the width of the popup list automatically adjusts according to the DropDownList input element’s width, and the height of the popup list has 350px. The height and width of the popup list can also be customized using the PopupHeight and PopupWidth properties respectively.

<SfDropDownList TValue="string" TItem="Games" PopupHeight="350px" PopupWidth="350px" Placeholder="Select a game" DataSource="@LocalData">
  <DropDownListFieldSettings Value="ID" Text="Text"></DropDownListFieldSettings>
</SfDropDownList>

@code{
  public class Games
  {
    public string ID { get; set; }
    public string Text { get; set; }
  }
  List<Games> LocalData = new List<Games> {
    new Games() { ID= "Game1", Text= "American Football" },
    new Games() { ID= "Game2", Text= "Badminton" },
    new Games() { ID= "Game3", Text= "Basketball" },
    new Games() { ID= "Game4", Text= "Cricket" },
    new Games() { ID= "Game5", Text= "Football" },
    new Games() { ID= "Game6", Text= "Golf" },
    new Games() { ID= "Game7", Text= "Hockey" },
    new Games() { ID= "Game8", Text= "Rugby"},
    new Games() { ID= "Game9", Text= "Snooker" },
    new Games() { ID= "Game10", Text= "Tennis"},
  };
}
Changing Popup List Height in Blazor DropDownList

Get selected value

Get the selected value of the DropDownList component in the ValueChange event using ChangeEventArgs.Value property.

  • CSHTML
  • @using Syncfusion.Blazor.DropDowns
    
    <SfDropDownList TValue="string" TItem="Games" Placeholder="Select a game" DataSource="@LocalData">
      <DropDownListFieldSettings Value="Text" Text="Text"></DropDownListFieldSettings>
      <DropDownListEvents TValue="string" TItem="Games" ValueChange="OnValueChange"></DropDownListEvents>
    </SfDropDownList>
    
    @code {
        public class Games
        {  
            public string ID { get; set; }
            public string Text { get; set; }
        }
        List<Games> LocalData = new List<Games> {
        new Games() { ID= "Game1", Text= "American Football" },
        new Games() { ID= "Game2", Text= "Badminton" },
        new Games() { ID= "Game3", Text= "Basketball" },
        new Games() { ID= "Game4", Text= "Cricket" },
        new Games() { ID= "Game5", Text= "Football" },
        new Games() { ID= "Game6", Text= "Golf" },
        new Games() { ID= "Game7", Text= "Hockey" },
        new Games() { ID= "Game8", Text= "Rugby"},
        new Games() { ID= "Game9", Text= "Snooker" },
        new Games() { ID= "Game10", Text= "Tennis"},
      };
        public void OnValueChange(ChangeEventArgs<string, Games> args)
        {
            Console.WriteLine("The DropDownList Value is: ", args.Value);
        }
    }

    Get the complete object list of the selected value in the ValueChange event using the ChangeEventArgs.ItemData property.

  • CSHTML
  • @using Syncfusion.Blazor.DropDowns
    
    <SfDropDownList TValue="string" TItem="Games" Placeholder="Select a game" DataSource="@LocalData">
      <DropDownListFieldSettings Value="ID" Text="Text"></DropDownListFieldSettings>
      <DropDownListEvents TValue="string" TItem="Games" ValueChange="OnValueChange"></DropDownListEvents>
    </SfDropDownList>
    
    @code {
        public class Games
        {  
            public string ID { get; set; }
            public string Text { get; set; }
        }
        List<Games> LocalData = new List<Games> {
        new Games() { ID= "Game1", Text= "American Football" },
        new Games() { ID= "Game2", Text= "Badminton" },
        new Games() { ID= "Game3", Text= "Basketball" },
        new Games() { ID= "Game4", Text= "Cricket" },
        new Games() { ID= "Game5", Text= "Football" },
        new Games() { ID= "Game6", Text= "Golf" },
        new Games() { ID= "Game7", Text= "Hockey" },
        new Games() { ID= "Game8", Text= "Rugby"},
        new Games() { ID= "Game9", Text= "Snooker" },
        new Games() { ID= "Game10", Text= "Tennis"},
      };
        public void OnValueChange(ChangeEventArgs<string, Games> args)
        {
            Console.WriteLine("The complete data of the selected value is: ", args.ItemData);
        }
    }

    See also