Conditional compilation depending on the Framework

Question

VC employment with Winforms, WPF and Asp.Net. All projects use the same dlls in C#.

I am trying to go from .Net framework 4.8 to .Net 8 and I need to include some code in some dlls so that, at compile time, it detects whether 4.8 or .Net is being used and, depending on the type of Framework, compiles certain lines or not . I may even need it to compile one function or another.

Is there any C# code example that shows how to do it?

Answer 1

Hi @zequion , Welcome to Microsoft Q&A,

Make sure that the correct compilation symbol definitions are included in the project file.

.NET Framework 4.8 project file (.csproj):

xmlCopy code
<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">

.NET 8 project file (.csproj):

xmlCopy code
<Project Sdk="Microsoft.NET.Sdk">

Create a class library project and use conditional compilation directives in your code. This class library will generate DLLs containing code for different frameworks.

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFrameworks>net48;net8.0</TargetFrameworks>
  </PropertyGroup>
  <PropertyGroup Condition="'$(TargetFramework)' == 'net48'">
    <DefineConstants>NET48</DefineConstants>
  </PropertyGroup>
  <PropertyGroup Condition="'$(TargetFramework)' == 'net8.0'">
    <DefineConstants>NET8</DefineConstants>
  </PropertyGroup>
</Project>

Use #if directives in shared class library projects to distinguish code from different frameworks.

using System;

public class FrameworkSpecificClass
{
    public void FrameworkSpecificMethod()
    {
        #if NET48
        Console.WriteLine("Running on .NET Framework 4.8");
        #elif NET8
        Console.WriteLine("Running on .NET 8");
        #else
        Console.WriteLine("Running on an unknown framework");
        #endif
    }

    public void SpecificMethod()
    {
        #if NET48
        SpecificMethodForNet48();
        #elif NET8
        SpecificMethodForNet8();
        #endif
    }

    #if NET48
    private void SpecificMethodForNet48()
    {
        Console.WriteLine("Specific method for .NET Framework 4.8");
    }
    #elif NET8
    private void SpecificMethodForNet8()
    {
        Console.WriteLine("Specific method for .NET 8");
    }
    #endif
}

Best Regards,

Jiale

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