Validation in custom handler

[Joe Terhune]

I have a custom handler that I am using to encrypt and store  uploaded tiff files to a database.  I want to add validation that would check the file to see if it is corrupt before saving. How do I send an error message back to the client?

[Hristo Valyavicharski]

Hi Joe,

You could return an error message as you change the result returned by the Handler's process method

protected override IAsyncUploadResult Process(UploadedFile file, HttpContext context, IAsyncUploadConfiguration configuration, string tempFileName)
{
    var queryStringParam1 = context.Request.QueryString["saveToFolder"];
    string targetFolder = context.Server.MapPath(configuration.TargetFolder);
    string fileName = file.GetName();

    CustomAsyncUploadResult result = CreateDefaultUploadResult<CustomAsyncUploadResult>(file);
    //file.SaveAs(targetFolder + "/" + fileName);

    if (true)
    {
        //Success
        result.ErrorMessage = String.Empty;
    }
    else
    {
        // Error. Set error message
        result.ErrorMessage = "File failed to upload in DB";
    }

    return result;
}

and then handle it on the client in OnClientFileUploaded event:

function OnClientFileUploaded(sender, args) {
    var msg = args.get_fileInfo().ErrorMessage;

    if (msg) {
        //Display error message
        $('#msg').text(msg);
        //Remove selected file
        $('.ruButton.ruRemove').click();
    }
}

For your reference I'm attaching small sample demonstrating how this code works. Additionally you could take a look at this online demo which implements the same approach.

Kind regards,
Hristo Valyavicharski
the Telerik team