The referenced assembly “Microsoft.SharePoint.Client.Runtime, …” could not be resolved…
You may see this error when you compile
The referenced assembly “Microsoft.SharePoint.Client.Runtime, Version=126.96.36.199, Culture=neutral, PublicKeyToken=71e9bce111e9429c, processorArchitecture=MSIL” could not be resolved because it has a dependency on “System.Web, Version=188.8.131.52, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a” which is not in the currently targeted framework “.NETFramework,Version=v4.0,Profile=Client”.
Go into the project settings. They are probably set to .NET 4.0 Framework. In order to use the ClientOM, set them the Framework to 3.5. The project will be unloaded and reloaded, so be sure to save your work before going into the properties canvas.
Next time you build an application intending to use the ClientOM, set the .NET Framework to 3.5 when creating the project.