AUTHOR: Marin Bratanov
DATE MODIFIED : September 21, 2017
DATE POSTED: December 12, 2016
500 (internal server error) in response to callbacks when Microsoft OWIN startup class code for authentication is used together with Telerik RadWindowManager for ASP.NET AJAX.
This also applies to controls that use RadWindowManager internally, like RadFileExplorer or some RadEditor dialogs.
The following two GitHub issues indicate that this may be an issue with the OWIN provider itself that may be fixed in later versions:
The issue stems from additional validation that the OWIN classes perform. If the page contains <input> elements without a name attribute, an error is thrown.
RadWindowManager contains an HTML template for RadPrompt that contains an <input> without a name attribute because the controls themselves do not add data to it, and it cannot be a part of the POST request, because any RadPrompt clones the template and does not use it in place.
Edit the PromptTemplate to add a desired name attribute or to remove the input entirely in case you application does not use the RadPrompt feature.
A small sample is attached that explains how to reproduce the issue so you can test out the solution for your setup. Note that you should keep the browser console open and monitor the network requests and that the site must be deployed to IIS.
For composite controls like RadFileExplorer, you can override the templates from the server. An additional sample is available that demonstrates the approach.
For the RadEditor dialogs, you will need to apply the approach from the Displaying single upload control in the FileBrowser Upload manager KB article to change the settings of the RadFileExplorer control inside. A sample is also available below. Versions prior to R1 2017 may still exhibit this issue because of several other input element whose name attributes need to be added from the server code.