The RadCloudUpload control does not expose the necessary property when the OnClientFileUploadRemoving event fires (using Azure).
To delete a file from Azure BLOB storage you need the keyname property. At the time of the OnClientFileUploadRemoving event, the only property exposed is the orignalFileName.
Azure creates a keyname to store the file. It consists of a GUID + the original file name, e.g., for a file named "test.txt" the keyname is "554cfa68-ee24-421f-94e8-7080cf70a11f_test.txt."
That's to allow for duplicate original file names in the container. The only way to delete a file from Azure storage is by the keyname property. That property is not exposed at the OnClientFileUploadRemoving event, so to be able to delete the file, you have to save that property in some other way at the time of uploading (in an array or database). That could fail. Obviously the control knows the keyname, as it is exposed when the file is uploaded, so it should store and expose that property.