I troubleshooted a piece of CSOM code in SharePoint 2013. I got the following error:
Method “GetList” does not exist
The reason was that the method GetList was not imlemented until March 2015 CU (15.0.4701.1001), and the SharePoint farm I had was SharePoint 2013 SP1 (15.0.4569.1000). So the solution is to install the Cumulative Update or use web.Lists.GetByTitle. GetByTitle has one aweful shortcoming: it doesn’t work in multilingual environments. So I have recommended to install the March 2015 CU.