SharePoint Client Side Object Model - Cannot Contact Site at the Specified URL - Mixed Authentication -

our sharepoint environment uses claims based authentication - using fba external users , ad internal users.

i have not been able connect using default credentials or windows authentication test sharepoint site using sharepoint client side object model (csom). able connect using fba user require connecting using default credentials (assuming app pool id tied sharepoint application) or @ least ad account.

the message when executing clientcontext.executequery - cannot contact site @ specified url. have researched extensively , have tried numerous suggestions including following:

1. using event handler tied clientcontext.executingwebrequest adds webrequest headers. solution found here https://social.technet.microsoft.com/forums/office/en-us/16cd0e26-8f3b-4ef2-bac4-c2c59849ab96/authentication-in-clientcontext-in-sharepoint-2010?forum=sharepointdevelopmentprevious.
2. using system.net.credentialcache.defaultcredentials
3. using system.net.networkcredential passing in ad account

thanks ideas or suggestions.

tom

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i should have mentioned using sharepoint 2010 , i'm trying retrieve , update user profile properties. beginning code solution (using fba connected clientcontext), read in sharepoint 2010, can update user properties using usergroup web service. access denied when trying connect via web service. believe clientcontext sits on top of web services scenario/issue same. again, thoughts or suggestions appreciated.

well, after research, seems there solution. adding header request programmatically first step. issue in addition adding header, must add additional windows authentication zone sharepoint. not want add zone our production environment.

since program i'm putting accesses sharepoint , non-sharepoint databases, run on non-sharepoint server use fba account created purpose.

in case interested, here link explaining how add header web request. receive error - object moved without adding additional zone. here link describes adding zone.