Используйте API Facebook, доступный на codeplex.com, и попробуйте это,
Facebook.Rest.attachment_media_image image1 = new attachment_media_image();
image1.href = "";
image1.src = "";
Facebook.Rest.attachment a = new Facebook.Rest.attachment();
a.media = new List<Facebook.Rest.attachment_media> { image1 };
a.href = "";
a.name = "";
a.caption = "{*actor*}";
a.properties = null;
if(fbapi.Users.HasAppPermission(Enums.ExtendedPermissions.publish_stream))
fbapi.Stream.Publish(" Your message, a,
new List<action_link>() { new action_link()
{ text = "",
href ="" }
},
null, 0);