This happens only when plugin is setup for an ajax mode for upload by setting the uploadUrl property of the plugin.
The following are the most likely reasons why this error is received.
- Check your server code. For an ajax mode, the bootstrap-fileinput plugin requires the server to send a valid JSON response. So the server action that you set in plugin uploadUrl MUST send a valid JSON. The format of JSON to be sent from server is described in the documentation for asynchronous ajax uploads and synchronous ajax uploads. Note that even if you do not have a valid JSON to send – you must ensure that you return at least an empty JSON object like below:
please how to upload in asp.net web site, using webmethod.what is the method for UploadURL, any exmaple