Description
What is the expected way of handling validation of a form field that is of type <input type="file">? Suppose that the form is bound to a model that has such a field and the form should display a validation message, when certain criteria is nto met, e.g. the file size exceeds a limit or the file has an invalid extension. Furthermore, what is the expected type of the model field that corresponds to <input type="file"> as things like IFormFIle
<EditForm
OnSubmit="@HandleSubmit"
EditContext="@_editContext">
<DataAnnotationsValidator />
<ValidationSummary />
<p>
<input type="file" @bind-value="_starship.File" />
</p>
<button type="submit">Submit</button>
</EditForm>
@code {
private Starship _starship = new Starship();
private EditContext _editContext;
protected override void OnInitialized()
{
_editContext = new EditContext(_starship);
}
private async Task HandleSubmit()
{
...
}
public class Starship
{
// custom validation attribute
[AllowedExtensionsAttribute(new string[] { ".txt" })]
public IFormFile File { get; set; }
}
}
fail with an exception (this is expected, but what should be the correct type):
The type 'Microsoft.AspNetCore.Http.IFormFile' does not have an
associated TypeConverter that supports conversion from a string.
Apply 'TypeConverterAttribute' to the type to register a converter.
Currently, there isn't a built in <InputFile> component and the blog post from @SteveSandersonMS doesn't mention form validation. In addition, will there be any built-in support for anti-forgery tokens as it is the case with MVC forms or should this be manually handled by the developer?
Will there be a difference whether wasm or server-side blazor is used?
Additional context
Building a custom <InputFile> component requires some type of validation when used in a form. Using a fully custom validation, e.g. manually displaying a message is possible, but this does not work with validation attributes at all.