There is no "get by URL" method for lists in the client object model that I am aware of.
About the closest thing you have is a GetFolderByServerRelativeUrl on the Web object:
ClientContext.Web.GetFolderByServerRelativeUrl(url)Depending on what you want to do this might work for you...unfortunately you can't get the parent list from the folder object like you can in the .NET api.
Source - Similar question
Since you can't get a list by URL so I would assume you can't get a document by url either, but you can try doing it this way tho,
var fileItem = Web.GetFileByServerRelativeUrl("server/relative/url");
context.Load(fileItem); //you will probably need to load the ListItemAllFields property here.
context.ExecuteQuery();
var listItem = fileItem.ListItemAllFields;
Console.WriteLine(listItem["Title"]);
Source - getlistitemstrurl-equivalent-for-clientcontext
Hope it helps :)
