What is the minimum .NET framework required for OData service development?
Is it possible to develop OData services in .NET Framework 4 & Microsoft ASP.NET Web API
But System.Web.OData is still not available.
Do I have to develop a project using .NET Framweork 4.5 (minimum) & Microsoft ASP.NET Web API 2
WebAPI/OData V4 is using .NET Framework 4.5, if you want to use .NET Framework 4, you can try with System.Web.Http.OData which is WebAPI/OData V3, but it's under maintanance, and won't add new features anymore, my recommandation is to move to use WebAPI/OData V4, or try Restier https://github.com/OData/RESTier if you just start to build an OData service.