RadControls for ASP.NET AJAX
The RadUpload control uses and extends the existing API of the
browsers and the .NET framework. However, due to some known restrictions, the control has
the limitations listed below:
RadUpload cannot upload files using AJAX calls. This is a limitation of
the XmlHttpRequest component, which is used in the AJAX frameworks for
asynchronous calls to the application. To upload a file you must perform a full page postback.
In most cases, it is possible to disable AJAX for a given submit button, to allow file uploads. Fortunately this is possible in
RadAsyncUpload - check the demo here.
RadUpload cannot check the size and the
mime-type of its selected files before an upload starts. This is because
of a security restriction of the JavaScript engine of popular browsers. You cannot access the client
file system with JavaScript, hence the inability to get the file size,
mime type or content. You can, however,
check the file size when the upload first starts.
Client-side validation is possible with RadAsyncUpload - check the demo here.
RadUpload cannot select multiple files in one file select box. This is a limitation of
the standard <input type=file> elements that RadUpload
uses for file selection. Currently, there are no plans for changing this restriction. You can check this code-library: How to upload multiple files using RadUpload (uploading .zip file and extract it on the server). In addition, this is possible in RadAsyncUpload - check the demo here.
RadUpload does not support initially selected files or allow file selections to persist
across postbacks. This is a security limitation of the standard <input type=file>
elements which it uses internally for file selection.
The file will not upload if you try to open the 'browse for file' window with javascript. Only the user can click
on the Select button and select a file.