ASP.Net 4.0 网站能否在仅支持 ASP.Net 4.8 框架的新服务器上运行

Question

I have an old website which was developed on.Net Framework 4.0 and client wants to move this website to new server which supports.Net 4.8 Framework.

I am afraid if website will work properly on.Net 4.8 framework as i am not sure if there is full backward compatibility.

Unfortunately i cant test it as i don't have access to new server.

My understanding is it should work and i should point framework to 4.8 in below line of cide in web.config <compilation debug="true" targetFramework="4.8" > i hope rest will work such as <add assembly="System.Web.Extensions.Design...... as all of them point to 4.0

<compilation debug="true" targetFramework="4.5" >
  <assemblies>
    <add assembly="System.Web.Extensions.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
    <add assembly="System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A" />
    <add assembly="System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
    <add assembly="System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
    <add assembly="System.Data.Linq, Version=4.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
    <!--  assembly doesnt work on MochaHost
     <add assembly="System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
    <add assembly="stdole, Version=7.0.3300.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
     -->
    <add assembly="System.Web.Abstractions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
    <add assembly="System.Web.Routing, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
    <add assembly="System.Data.Entity, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
    <add assembly="Microsoft.Office.Interop.Excel, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71E9BCE111E9429C" />
    <add assembly="Microsoft.Office.Interop.Word, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71E9BCE111E9429C" />
    <!---->
  </assemblies>
</compilation>

Answer 1

.NET 4.8 is an 'extension' on .NET 4.0. Microsoft tries it's best to be backwards compatible, you can check https://learn.microsoft.com/en-us/do.net/framework/migration-guide/runtime/4.0-4.8 for seeing what can break if you run your website (or any other program compiled in .NET 4.0) on the .NET 4.8 runtime. Most breaking changes have a switch that you can return to the older behavior, see the link above.

You don't even have to change the target framework in the config. Changing the <compilation targetFramework="4.8" > will cause the website to be compiled under 4.8 (if it hasn't been pre-compiled) on the first request, which has it's own set of changes that can be viewed on the page https://learn.microsoft.com/en-us/do.net/framework/migration-guide/retargeting/4.0-4.8 .

In case of doubt, you can install IIS on a test computer or your local computer, configure the website and test before you release on the new server.