Validation in Blazor File Upload Component

23 Aug 20237 minutes to read

The uploader component validate the selected files size and extension using the AllowedExtensions, MinFileSize and MaxFileSize properties. The files can be validated before uploading to the server and can be ignored on uploading. Also, you can validate the files by setting the HTML attributes to the original input element. The validation process occurs on drag-and-drop the files also.

File type

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.

SaveUrl and RemoveUrl actions are explained in this link.

@using Syncfusion.Blazor.Inputs

<SfUploader ID="UploadFiles" AllowedExtensions=".doc, .docx, .xls, .xlsx">
 <UploaderAsyncSettings SaveUrl="api/SampleData/Save" RemoveUrl="api/SampleData/Remove">
 </UploaderAsyncSettings>
</SfUploader>

File size

The uploader component allows you to validate the files based on its size. The validation helps to restrict uploading large files or empty files to the server. The size can be represented in bytes. By default, the uploader component allows you to upload minimum file size as 0 byte and maximum file size as 28.4 MB using the MinFileSize and MaxFileSize properties.

SaveUrl and RemoveUrl actions are explained in this link.

@using Syncfusion.Blazor.Inputs

<SfUploader ID="UploadFiles" AllowedExtensions=".doc, .docx, .xls, .xlsx"  MinFileSize=10000 MaxFileSize=1000000>
    <UploaderAsyncSettings SaveUrl="api/SampleData/Save" RemoveUrl="api/SampleData/Remove">
    </UploaderAsyncSettings>
</SfUploader>

File Validation within Edit Form

The provided code snippet demonstrates a Blazor form for editing employee information, including uploader component. It incorporates data validation and displays error messages. Users can select files for upload, which are stored in the files property of the Employee model. The code handles file selection, changes, and removal through the use of the FileSelect, ValueChange, and OnRemove events. Additionally, it enables manual file upload during form submission.

Without server-side API endpoint

@using System.ComponentModel.DataAnnotations
@using Syncfusion.Blazor.Inputs

 <EditForm Model="@employee" OnValidSubmit="@HandleValidSubmit" OnInvalidSubmit="@HandleInvalidSubmit">  
        <DataAnnotationsValidator />  
        <div class="form-group">  
           <SfTextBox @bind-Value="@employee.EmpID"></SfTextBox>  
           <ValidationMessage For="() => employee.EmpID" /> 
        </div>  
        <div class="form-group">  
            <SfUploader @ref="UploadObj" AllowMultiple=false AutoUpload="false" ID="UploadFiles">  
                <UploaderEvents ValueChange="OnChange" OnRemove="OnRemove" FileSelected="OnSelect"></UploaderEvents>  
            </SfUploader>  
            <ValidationMessage For="() => employee.files" /> 
        </div>  
        <button type="submit" class="btn btn-primary">Submit</button>  
    </EditForm>  
  
@code{
    SfUploader UploadObj;  
    public class Employee 
    { 
        [Required(ErrorMessage ="Please enter your name")] 
        public string EmpID { get; set; } 

        [Required(ErrorMessage = "Please upload a file")] 
        public List<UploaderUploadedFiles> files { get; set; } 
    } 
    public Employee employee = new Employee();  

    public void OnSelect(SelectedEventArgs args) 
    {   
        this.employee.files = new List<UploaderUploadedFiles>() { new UploaderUploadedFiles() { Name = args.FilesData[0].Name, Type = args.FilesData[0].Type, Size = args.FilesData[0].Size } }; 
    } 
    private async Task OnChange(UploadChangeEventArgs args)  
    {  
        foreach (var file in args.Files)  
        {
            if (file.FileInfo != null && file.File != null)
            {
                var path = @"" + file.FileInfo.Name;

                FileStream filestream = new FileStream(path, FileMode.Create, FileAccess.Write);

                await file.File.OpenReadStream(long.MaxValue).CopyToAsync(filestream);

                filestream.Close();
            }
        }  
    }  
    public void OnRemove() 
    { 
        this.employee.files = null; 
    } 
 
    public async Task HandleValidSubmit()  
    {  
        await this.UploadObj.Upload(); // Upload the selected file manually  
 
    }   
    public async Task HandleInvalidSubmit() 
    { 
         await this.UploadObj.Upload(); // Upload the selected file manually  
    }  
}

With server-side API endpoint

@using System.ComponentModel.DataAnnotations
@using Syncfusion.Blazor.Inputs

 <EditForm Model="@employee" OnValidSubmit="@HandleValidSubmit" OnInvalidSubmit="@HandleInvalidSubmit">  
        <DataAnnotationsValidator />  
        <div class="form-group">  
           <SfTextBox @bind-Value="@employee.EmpID"></SfTextBox>  
           <ValidationMessage For="() => employee.EmpID" /> 
        </div>  
        <div class="form-group">  
            <SfUploader @ref="UploadObj" AllowMultiple=false AutoUpload="false" ID="UploadFiles"> 
             <UploaderAsyncSettings SaveUrl="https://aspnetmvc.syncfusion.com/services/api/uploadbox/Save"
                           RemoveUrl="https://aspnetmvc.syncfusion.com/services/api/uploadbox/Remove"></UploaderAsyncSettings> 
                <UploaderEvents OnRemove="OnRemove" FileSelected="OnSelect"></UploaderEvents>  
            </SfUploader>  
            <ValidationMessage For="() => employee.files" /> 
        </div>  
        <button type="submit" class="btn btn-primary">Submit</button>  
    </EditForm>  
  
@code{
    SfUploader UploadObj;  
    public class Employee 
    { 
        [Required(ErrorMessage ="Please enter your name")] 
        public string EmpID { get; set; } 

        [Required(ErrorMessage = "Please upload a file")] 
        public List<UploaderUploadedFiles> files { get; set; } 
    } 
    public Employee employee = new Employee();  

    public void OnSelect(SelectedEventArgs args) 
    {   
        this.employee.files = new List<UploaderUploadedFiles>() { new UploaderUploadedFiles() { Name = args.FilesData[0].Name, Type = args.FilesData[0].Type, Size = args.FilesData[0].Size } }; 
    }
    public void OnRemove() 
    { 
        this.employee.files = null; 
    } 
 
    public async Task HandleValidSubmit()  
    {  
        await this.UploadObj.Upload(); // Upload the selected file manually  
 
    }   
    public async Task HandleInvalidSubmit() 
    { 
         await this.UploadObj.Upload(); // Upload the selected file manually  
    }  
}