According to the .NET Framework library for Silverlight, a schema Urican be 1024, and a full one Urican be up to 65519 characters. This is true for both v3 and v4.
Hope this gives you some tips.
EDIT
Ok, ok, after a lot of testing, I was able to track the limit for the image URL.
The scheme refers to the part http.
The whole Uricannot be longer than 2047 , after which it seems that it no longer uploads the image. However, I could not find any official arguments.
The fact that you get exceptions AG_E_NETWORK_ERRORhas nothing to do with length Uri.
However, you can check to see if there are any illegal characters in your URI:
, XAML, '&' "% 26".