Blazor File Upload Component in WebAssembly App using Visual Studio

24 Jan 202210 minutes to read

This article provides a step-by-step instructions for building Blazor WebAssembly App with Blazor File Upload component using Visual Studio.

Prerequisites

Create a Blazor WebAssembly App in Visual Studio

You can create Blazor WebAssembly App using Visual Studio in one of the following ways,

Install Syncfusion Blazor Inputs NuGet in the App

Syncfusion Blazor components are available in nuget.org. To use Syncfusion Blazor components in the application, add reference to the corresponding NuGet. Refer to NuGet packages topic for available NuGet packages list with component details.

To add Blazor File Upload component in the app, open the NuGet package manager in Visual Studio (Tools → NuGet Package Manager → Manage NuGet Packages for Solution), search for Syncfusion.Blazor.Inputs and then install it.

Register Syncfusion Blazor Service

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

@using Syncfusion.Blazor

Now, Open ~/Program.cs file and register the Syncfusion Blazor Service in the client web app. Here, Syncfusion Blazor Service is registered by setting IgnoreScriptIsolation property as true to load the scripts externally in the next steps.

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(options => { options.IgnoreScriptIsolation = true; });
await builder.Build().RunAsync();
....
using Syncfusion.Blazor;

namespace BlazorApplication
{
    public class Program
    {
        public static async Task Main(string[] args)
        {
            ....
            builder.Services.AddSyncfusionBlazor(options => { options.IgnoreScriptIsolation = true; });
            await builder.Build().RunAsync();
        }
    }
}

Add Style Sheet

Checkout the Blazor Themes topic to learn different ways (Static Web Assets, CDN and CRG) to refer themes in Blazor application, and to have the expected appearance for Syncfusion Blazor components. Here, the theme is referred using Static Web Assets.

To add theme to the app, open the NuGet package manager in Visual Studio (Tools → NuGet Package Manager → Manage NuGet Packages for Solution), search for Syncfusion.Blazor.Themes and then install it. Then, the theme style sheet from NuGet can be referred inside the <head> of wwwroot/index.html file in client web app.

<head>
    ...
    <link href="_content/Syncfusion.Blazor.Themes/bootstrap5.css" rel="stylesheet" />
</head>

Add Script Reference

Checkout Adding Script Reference topic to learn different ways to add script reference in Blazor Application. In this getting started walk-through, the required scripts are referred using Static Web Assets externally inside the <head> of wwwroot/index.html file in client web app.

<head>
    ...
    <link href="_content/Syncfusion.Blazor.Themes/bootstrap5.css" rel="stylesheet" />
    <script src="https://cdn.syncfusion.com/blazor/19.4.38/syncfusion-blazor.min.js" type="text/javascript"></script>
</head>

Syncfusion recommends to reference scripts using Static Web Assets, CDN and CRG by disabling JavaScript isolation for better loading performance of the Blazor application. Generate scripts and theme assets using CRG by selecting the components you were using in the application.

Add Blazor File Upload component

  • Open ~/_Imports.razor file or any other page under the ~/Pages folder where the component is to be added and import the Syncfusion.Blazor.Inputs namespace.
@using Syncfusion.Blazor
@using Syncfusion.Blazor.Inputs
  • Now, add the Syncfusion File Upload component in razor file. Here, the File Upload component is added in the ~/Pages/Index.razor file under the ~/Pages folder.
<SfUploader></SfUploader>
  • Press Ctrl+F5 (Windows) or +F5 (macOS) to run the app. Then, the Syncfusion Blazor File Upload component will be rendered in the default web browser.

Blazor Upload

Without server-side API endpoint

You can upload the files and files of folders in the Blazor application without specifying the server-side API end point using AsyncSettings.

Save and Remove actions

You can get the uploaded files as file stream in the ValueChange event argument. Now, you can write the save handler inside ValueChange event to save the files to desired location. Please find the save action code on below.

<SfUploader AutoUpload="false">
    <UploaderEvents ValueChange="OnChange"></UploaderEvents>
</SfUploader>

@code {

    private void OnChange(UploadChangeEventArgs args)
    {
        foreach (var file in args.Files)
        {
            var path = @"path" + file.FileInfo.Name;
            FileStream filestream = new FileStream(path, FileMode.Create, FileAccess.Write);
            file.Stream.WriteTo(filestream);
            filestream.Close();
            file.Stream.Close();
        }
    }
}

Blazor FileUpload displays Updated Files

While clicking on the remove icon in the file list, you will get the OnRemove event with removing file name as argument. So, you can write the remove handler inside OnRemove event to remove the particular file from desired location. Please find the remove action code on below.

Private void onRemove(RemovingEventArgs args)
{
    foreach(var removeFile in args.FilesData)
    {
        if (File.Exists(Path.Combine(@"rootPath", removeFile.Name)))
        {
            File.Delete(Path.Combine(@"rootPath", removeFile.Name))
        }
    }
}

With server-side API endpoint

The upload process requires save and remove action URL to manage the upload process in the server.

  • The save action is necessary to handle the upload operation.
  • The remove action is optional, one can handle the removed files from server.

The save action handler upload the files that needs to be specified in the SaveUrl property.

The save handler receives the submitted files and manages the save process in server. After uploading the files to server location, the color of the selected file name changes to green and the remove icon is changed as bin icon.

The remove action is optional. The remove action handler removes the files that needs to be specified in the RemoveUrl property.

[Route("api/[controller]")]

private IHostingEnvironment hostingEnv;

public SampleDataController(IHostingEnvironment env)
{
    this.hostingEnv = env;
}

[HttpPost("[action]")]
public void Save(IList<IFormFile> UploadFiles)
{
    long size = 0;
    try
    {
        foreach (var file in UploadFiles)
        {
            var filename = ContentDispositionHeaderValue
                    .Parse(file.ContentDisposition)
                    .FileName
                    .Trim('"');
                filename = hostingEnv.ContentRootPath + $@"\{filename}";
                size += (int)file.Length;
            if (!System.IO.File.Exists(filename))
            {
                using (FileStream fs = System.IO.File.Create(filename))
                {
                    file.CopyTo(fs);
                    fs.Flush();
                }
            }
        }
    }
    catch (Exception e)
    {
        Response.Clear();
        Response.StatusCode = 204;
        Response.HttpContext.Features.Get<IHttpResponseFeature>().ReasonPhrase = "File failed to upload";
        Response.HttpContext.Features.Get<IHttpResponseFeature>().ReasonPhrase = e.Message;
    }
}
[HttpPost("[action]")]
public void Remove(IList<IFormFile> UploadFiles)
{
    try
    {
        var filename = hostingEnv.ContentRootPath + $@"\{UploadFiles[0].FileName}";
        if (System.IO.File.Exists(filename))
        {
            System.IO.File.Delete(filename);
        }
    }
    catch (Exception e)
    {
        Response.Clear();
        Response.StatusCode = 200;
        Response.HttpContext.Features.Get<IHttpResponseFeature>().ReasonPhrase = "File removed successfully";
        Response.HttpContext.Features.Get<IHttpResponseFeature>().ReasonPhrase = e.Message;
    }
}
<SfUploader ID="UploadFiles">
    <UploaderAsyncSettings SaveUrl="api/SampleData/Save" RemoveUrl="api/SampleData/Remove"></UploaderAsyncSettings>
</SfUploader>

Configure allowed file types

You can allow the specific files alone to upload using the AllowedExtensions property. The extension can be represented as collection by comma separators. The uploader component filters the selected or dropped files to match against the specified file types and processes the upload operation. The validation happens when you specify value to inline attribute to accept the original input element.

<SfUploader AllowedExtensions=".doc, docx, .xls, xlsx"></SfUploader>

Allowing Specific Files in Blazor FileUpload

See Also