使用指令预处理器处理多个目标框架

Question

I create a Net Standard class library targeting Net Standard 2.0 and Net Framework 4.6.2 to handle the two frameworks. In Net Framework I need to distinguish if it's a Web API project or Web Application project. This is what I want.

using System;
using System.Linq;

#if (netcoreapp2.0 || netcoreapp2.1)
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
#endif

//net462 || net47 || net471 || net472
#if (NETFX)
using System.Net.Http;
using System.Web;
using System.Web.Mvc;
#endif

namespace TestNetStandard
{
    //FOR NET MVC WEB
    public class ExceptionValidationAttribute : System.Web.Mvc.IExceptionFilter
    {
    }

    //FOR NET MVC API
    public class ExceptionValidationAttribute : System.Web.Http.Filters.ExceptionFilterAttribute
    {
    }

    //For NET CORE
    public class ExceptionValidationAttribute : Microsoft.AspNetCore.Mvc.Filters.ExceptionFilterAttribute
    {
    }
}

So, is it possible to create single class using preprocessor directive while the ExceptionValidationAttribute class inherits different classes? If yes, how to accomplish this scenario?

Answer 1

You can try something like this

#if ASPNETMVC
using ExceptionValidationAttributeParent = System.Web.Mvc.IExceptionFilter;
#elif ASPNETWEBAPI
using ExceptionValidationAttributeParent = System.Web.Http.Filters.ExceptionFilterAttribute;
#elif ASPNETCORE
using ExceptionValidationAttributeParent = Microsoft.AspNetCore.Mvc.Filters.ExceptionFilterAttribute;
#else
// default case but maybe redundant 
using ExceptionValidationAttributeParent = SomeFakeParentClass;
#endif



namespace TestNetStandard
{
    public class ExceptionValidationAttribute : ExceptionValidationAttributeParent
    {
        ...
    }
}