Question

I have a file upload feature in my MVC 3 web application and I’m trying to validate FileSize and FileType using those attributes:

[FileSize(1048576, ErrorMessage = "The image is too big. It should be up to 1MB")]
[FileType(MimeTypes.Image.Jpg, MimeTypes.Image.Jpeg, MimeTypes.Image.Png, "image/pjpeg", "image/x-png", ErrorMessage = "Your image must be a JPG/JPEG or PNG up to 1MB.")]
public HttpPostedFileBase File { get; set; }

HTML is as follows:

<input type="file" size="20" name="File" />
@Html.ValidationMessageFor(x => x.File)

Everything works perfect when the file is selected. But if there is no file selected, I still get FileSize or FileType validation fired and validation errors. How can I avoid this since I don’t want File to be required on POST?

Answer 1

You will have to modify the FileSize and FileType custom validation attributes so that do not perform any validation if the value is null. For example:

public class FileSizeAttribute : ValidationAttribute
{
    protected override ValidationResult IsValid(object value, ValidationContext validationContext)
    {
        if (value == null)
        {
            // don't validate if value is null
            return null;
        }

        // TODO: do whatever validation you were supposed to do
        ...
    }
}

And it is via the [Required] attribute that you could make the file required.