Getting Started with Blazor MultiSelect DropDown in WASM App

24 Dec 20259 minutes to read

This guide explains how to add the Blazor MultiSelect Dropdown component to a Blazor WebAssembly app using Visual Studio, Visual Studio Code, and the .NET CLI.

To get started quickly with the Blazor MultiSelect Dropdown component, refer to this GitHub sample.

Prerequisites

Create a new Blazor App in Visual Studio

Create a Blazor WebAssembly App using Visual Studio via Microsoft Templates or the Syncfusion® Blazor Extension. For detailed instructions, refer to the Blazor WASM App Getting Started documentation.

Blazor WASM Create Project Template

Install Syncfusion® Blazor DropDowns and Themes NuGet in the App

To add the Blazor MultiSelect Dropdown component, open the NuGet Package Manager in Visual Studio (Tools → NuGet Package Manager → Manage NuGet Packages for Solution), then search and install Syncfusion.Blazor.DropDowns and Syncfusion.Blazor.Themes. Alternatively, run the following commands in the Package Manager Console to achieve the same.

Install-Package Syncfusion.Blazor.DropDowns -Version 32.1.19
Install-Package Syncfusion.Blazor.Themes -Version 32.1.19

NOTE

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

Prerequisites

Create a new Blazor App in Visual Studio Code

Create a Blazor WebAssembly App using Visual Studio Code via Microsoft Templates or the Syncfusion® Blazor Extension. For detailed instructions, refer to the Blazor WASM App Getting Started documentation.

Alternatively, create a WebAssembly application by using the following command in the integrated terminal(Ctrl+`).

dotnet new blazorwasm -o BlazorApp
cd BlazorApp

Install Syncfusion® Blazor DropDowns and Themes NuGet in the App

  • Press Ctrl+` to open the integrated terminal in Visual Studio Code.
  • Ensure in the project root directory where the .csproj file is located.
  • Run the following commands to install the Syncfusion.Blazor.DropDowns and Syncfusion.Blazor.Themes NuGet packages and ensure all dependencies are installed.
dotnet add package Syncfusion.Blazor.DropDowns -v 32.1.19
dotnet add package Syncfusion.Blazor.Themes -v 32.1.19
dotnet restore

NOTE

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

Prerequisites

Install the latest version of .NET SDK. If the .NET SDK is already installed, determine the installed version by running the following command in a command prompt (Windows), terminal (macOS), or command shell (Linux).

dotnet --version

Create a Blazor WebAssembly App using .NET CLI

Run the following command to create a new Blazor WebAssembly App in a command prompt (Windows) or terminal (macOS) or command shell (Linux). For detailed instructions, refer to this Blazor WASM App Getting Started documentation.

dotnet new blazorwasm -o BlazorApp
cd BlazorApp

Install Syncfusion® Blazor DropDowns and Themes NuGet in the App

To add the Blazor MultiSelect Dropdown component to the application, run the following commands in a command prompt (Windows), command shell (Linux), or terminal (macOS) to install the Syncfusion.Blazor.DropDowns and Syncfusion.Blazor.Themes. See Install and manage packages using the dotnet CLI for more details.

dotnet add package Syncfusion.Blazor.DropDowns -Version 32.1.19
dotnet add package Syncfusion.Blazor.Themes -Version 32.1.19
dotnet restore

NOTE

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

Add Import Namespaces

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

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

Register Syncfusion® Blazor Service

Register the Syncfusion® Blazor Service in the ~/Program.cs file of the Blazor WebAssembly App.

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. Include the stylesheet and script references in the <head> section of the ~/index.html.

<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>

    //Blazor MultiSelect DropDown Component script reference.
    <!-- <script src="_content/Syncfusion.Blazor.DropDowns/scripts/sf-multiselect.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 Blazor application. Also, check out the Adding Script Reference topic to learn different approaches for adding script references in Blazor application.

Add Blazor MultiSelect component

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

<SfMultiSelect TValue="string[]" TItem="string" Placeholder='First Name'></SfMultiSelect>
  • Press Ctrl+F5 (Windows) or ⌘+F5 (macOS) to launch the application. This will render the Syncfusion® Blazor MultiSelect DropDown component in the default web browser.
Blazor MultiSelect DropDown Component

Binding data source

After initialization, populate the MultiSelect using the DataSource property. In the following example, a list of objects is bound to the component, and TItem specifies the data type. Display and value fields are mapped via MultiSelectFieldSettings.

<SfMultiSelect TValue="string[]" TItem="Games" Placeholder="Favorite Sports" DataSource="@LocalData">
    <MultiSelectFieldSettings Text="Text" Value="ID"></MultiSelectFieldSettings>
</SfMultiSelect>

@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 MultiSelect DropDown

Configure the popup list

By default, the popup list width automatically adjusts to the MultiSelect input width, and the height auto-adjusts to the number of items.

Customize the popup size by setting PopupHeight and PopupWidth.

<SfMultiSelect TValue="string[]" TItem="Games" Placeholder="Favorite Sports" PopupHeight="350px" PopupWidth="350px" DataSource="@LocalData">
    <MultiSelectFieldSettings Text="Text" Value="ID"></MultiSelectFieldSettings>
</SfMultiSelect>
Configuring Popup List in Blazor MultiSelect Dropdown

Get selected value

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

  • CSHTML
    • @using Syncfusion.Blazor.DropDowns

<SfMultiSelect TValue="string[]" TItem="Games" Placeholder="Select a game" DataSource="@LocalData">
    <MultiSelectFieldSettings Value="Text" Text="Text"></MultiSelectFieldSettings>
    <MultiSelectEvents TValue="string[]" TItem="Games" ValueChange="OnValueChange"></MultiSelectEvents>
</SfMultiSelect>

@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(MultiSelectChangeEventArgs<string[]> args)
    {
        Console.WriteLine("The MultiSelect Value is: ", args.Value);
    }
}

    See also