I'm using ASP.NET Core 2.2 and I'm using model binding for uploading file.
This is my UserViewModel
public class UserViewModel
{
[Required(ErrorMessage = "Please select a file.")]
[DataType(DataType.Upload)]
public IFormFile Photo { get; set; }
}
This is MyView
@model UserViewModel
<form method="post"
asp-action="UploadPhoto"
asp-controller="TestFileUpload"
enctype="multipart/form-data">
<div asp-validation-summary="ModelOnly" class="text-danger"></div>
<input asp-for="Photo" />
<span asp-validation-for="Photo" class="text-danger"></span>
<input type="submit" value="Upload"/>
</form>
And finally this is MyController
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> UploadPhoto(UserViewModel userViewModel)
{
if (ModelState.IsValid)
{
var formFile = userViewModel.Photo;
if (formFile == null || formFile.Length == 0)
{
ModelState.AddModelError("", "Uploaded file is empty or null.");
return View(viewName: "Index");
}
var uploadsRootFolder = Path.Combine(_environment.WebRootPath, "uploads");
if (!Directory.Exists(uploadsRootFolder))
{
Directory.CreateDirectory(uploadsRootFolder);
}
var filePath = Path.Combine(uploadsRootFolder, formFile.FileName);
using (var fileStream = new FileStream(filePath, FileMode.Create))
{
await formFile.CopyToAsync(fileStream).ConfigureAwait(false);
}
RedirectToAction("Index");
}
return View(viewName: "Index");
}
How can I limit uploaded files to lower than 5MB with specific extensions like .jpeg and .png ? I think both of these validations are done in the ViewModel. But I don't know how to do that.
You could custom validation attribute MaxFileSizeAttribute like below
MaxFileSizeAttribute
public class MaxFileSizeAttribute : ValidationAttribute
{
private readonly int _maxFileSize;
public MaxFileSizeAttribute(int maxFileSize)
{
_maxFileSize = maxFileSize;
}
protected override ValidationResult IsValid(
object value, ValidationContext validationContext)
{
var file = value as IFormFile;
if (file != null)
{
if (file.Length > _maxFileSize)
{
return new ValidationResult(GetErrorMessage());
}
}
return ValidationResult.Success;
}
public string GetErrorMessage()
{
return $"Maximum allowed file size is { _maxFileSize} bytes.";
}
}
AllowedExtensionsAttribute
public class AllowedExtensionsAttribute : ValidationAttribute
{
private readonly string[] _extensions;
public AllowedExtensionsAttribute(string[] extensions)
{
_extensions = extensions;
}
protected override ValidationResult IsValid(
object value, ValidationContext validationContext)
{
var file = value as IFormFile;
if (file != null)
{
var extension = Path.GetExtension(file.FileName);
if (!_extensions.Contains(extension.ToLower()))
{
return new ValidationResult(GetErrorMessage());
}
}
return ValidationResult.Success;
}
public string GetErrorMessage()
{
return $"This photo extension is not allowed!";
}
}
Add MaxFileSize attribute and AllowedExtensions attribute to Photo property
public class UserViewModel
{
[Required(ErrorMessage = "Please select a file.")]
[DataType(DataType.Upload)]
[MaxFileSize(5* 1024 * 1024)]
[AllowedExtensions(new string[] { ".jpg", ".png" })]
public IFormFile Photo { get; set; }
}
You can implement IValidatableObject to validate your model.
public class UserViewModel : IValidatableObject { [Required(ErrorMessage = "Please select a file.")] [DataType(DataType.Upload)] public IFormFile Photo { get; set; } public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) { var photo = ((UserViewModel)validationContext.ObjectInstance).Photo; var extension = Path.GetExtension(photo.FileName); var size = photo.Length; if (!extension.ToLower().Equals(".jpg")) yield return new ValidationResult("File extension is not valid."); if(size > (5 * 1024 * 1024)) yield return new ValidationResult("File size is bigger than 5MB."); } }Following previous comment, you can add this class:
public class ValidateModelStateFilter : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext context)
{
if (context.ModelState.IsValid)
{
return;
}
var validationErrors = context.ModelState
.Keys
.SelectMany(k => context.ModelState[k].Errors)
.Select(e => e.ErrorMessage)
.ToArray();
var json = new JsonErrorResponse
{
Messages = validationErrors
};
context.Result = new BadRequestObjectResult(json);
}
}
Finally, add the filter to the controllers in Startup class:
services.AddControllers(options =>
{
options.Filters.Add(typeof(ValidateModelStateFilter));
})