Blazor FileInput

<FileInput HintText="Select a file with the standard Bootstrap file control." />

<FileInput Multiple="true" HintText="Select multiple files, then remove individual files from the list." />

<div class="vstack gap-3">
    <FileInput Size="FileInputSize.Large" HintText="Large file input." />
    <FileInput Size="FileInputSize.Small" HintText="Small file input." />
</div>

<FileInput Multiple="true"
           MaxFileCount="3"
           MaxFileSize="1048576"
           AllowedFileTypes="@allowedFileTypes"
           InvalidFileTypeErrorMessage="{FileName} must use one of: {AllowedFileTypes}."
           MaxFileCountErrorMessage="{FileName} would exceed the {MaxFileCount}-file limit."
           MaxFileSizeErrorMessage="{FileName} exceeds the {MaxFileSize}-byte limit."
           SingleFileErrorMessage="Select only one file."
           HintText="Select up to three PDF or PNG files, each no larger than 1 MB." />

@code {
    private readonly string[] allowedFileTypes = [".pdf", "png"];
}

@using System.ComponentModel.DataAnnotations
@using Microsoft.AspNetCore.Components.Forms

<EditForm EditContext="@editContext" OnValidSubmit="HandleValidSubmit">
    <DataAnnotationsValidator />
    <ValidationSummary />

    <div class="mb-3">
        <label class="form-label">Supporting document <span class="text-danger">*</span></label>
        <FileInput AllowedFileTypes="@allowedFileTypes"
                   MaxFileSize="1048576"
                   FilesChanged="OnFilesChanged"
                   HintText="A PDF document up to 1 MB is required." />
        <ValidationMessage For="@(() => upload.DocumentName)" />
    </div>

    <Button Type="ButtonType.Submit" Color="ButtonColor.Primary">Submit</Button>

    @if (submitted)
    {
        <div class="alert alert-success mt-3" role="status">Form submitted with @upload.DocumentName.</div>
    }
</EditForm>

@code {
    private readonly string[] allowedFileTypes = ["pdf"];
    private readonly UploadModel upload = new();
    private EditContext editContext = null!;
    private bool submitted;

    protected override void OnInitialized()
    {
        editContext = new EditContext(upload);
    }

    private void HandleValidSubmit() => submitted = true;

    private void OnFilesChanged(IReadOnlyList<IBrowserFile> files)
    {
        upload.DocumentName = files.FirstOrDefault()?.Name;
        submitted = false;
        editContext.NotifyFieldChanged(new FieldIdentifier(upload, nameof(upload.DocumentName)));
    }

    private sealed class UploadModel
    {
        [Required(ErrorMessage = "A supporting document is required.")]
        public string? DocumentName { get; set; }
    }
}

<FileInput Multiple="true"
           AllowedFileTypes="@allowedFileTypes"
           MaxFileSize="5242880"
           HintText="Any extension is accepted because the allowed-extension collection is empty; the 5 MB size limit still applies." />

@code {
    private readonly string[] allowedFileTypes = [];
}