"The input is not a valid Base-64 string.." error when using file upload

Question

I need to have a file upload on my view. To not mess with HttpPostedFileBase but rather to be able to use byte array for model binding I decided to extend ByteArrayModelBinder and implement it so that it automatically conerts HttpPostFileBase to byte[]. Here's how I did this:

public class CustomByteArrayModelBinder : ByteArrayModelBinder
{
    public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            var file = controllerContext.HttpContext.Request.Files[bindingContext.ModelName];
     
            if (file != null)
            {
                if (file.ContentLength > 0)
                {
                    var fileBytes = new byte[file.ContentLength];
                    file.InputStream.Read(fileBytes, 0, fileBytes.Length);
                    return fileBytes;
                }
     
                return null;
            }
     
            return base.BindModel(controllerContext, bindingContext);
        }
    }

    protected void Application_Start()
    {
        ...
        ModelBinders.Binders.Remove(typeof(byte[]));
        ModelBinders.Binders.Add(typeof(byte[]), new CustomByteArrayModelBinder());
    }

After doing above I was supposed to be able to have a ViewModel like this:

    public class Profile
{
    public string Name {get; set;}
    public int Age{get; set;}
    public byte[] photo{get; set;}
}

In the view I create the corresponding html element like this:

@using (Html.BeginForm(null,null,FormMethod.Post,new { enctype = "multipart/form-data" })){
.........    
@Html.TextBoxFor(x=>x.photo,new{type="file"})
<input type="submit" valaue="Save">
}

But when I submit the form I get the following error:

The input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or a non-white space character among the padding characters.

In fact it's not my idea, I following th guide in this link. Don't know what to do because the execution stops at this line:

 return base.BindModel(controllerContext, bindingContext);

Any ideas what to do?

EDIT: Controller action method:

 [HttpPost]
 public ActionResult Save(Profile profile){
     if(ModelIsValid){
        context.SaveProfile(profile);
     }
 }

But the action method is not even reached. The problem occurs prior to the action method.

@Overmachine, please see the edit, I've added the action method. but the error occurs prior to the action method. — Mikayil Abdullayev
– Mikayil Abdullayev, Commented Jul 21, 2014 at 18:35
I just tested the code on the linl and everything works fine, the only thing that comes up to my mind are the typos on the html you provided :/ like @Html.TextBox|For should be @TextBoxFor() — Overmachine
– Overmachine, Commented Jul 21, 2014 at 18:58

Kartikeya Khosla · Accepted Answer · 2014-07-22 04:37:30Z

1

Sometimes while converting base64, the + and / characters are changed to - and _. So u have to replace them as :

string converted = base64String.Replace('-', '+');
converted = converted.Replace('_', '/');

in ur BindModel class.

answered Jul 22, 2014 at 4:37

Kartikeya Khosla

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