I suggest you using the OnClientFileSelected
for more details about this client-side event and a sample code-snippet demonstrating its use.
to get the input field of the selected file which the eventArgs of the OnClientFileSelected
provide. However, if you want to avoid someone type a path in the file input field instead of using the Browse dialog for selecting a file you can set the ReadOnlyFileInputs
property of the RadUpload control to true
the Telerik team