How to do use .NET Framework 4.0 project execute .NET 7.0 Project in C#

My company has a solution, the project is a Winforms app running on .NET Framework 4.0.

I add a new project on .NET 7.0 to the solution, and I went to use through Framework 4.0 Project execute Net 7.0 Project .

I include using the net 7.0 dll and I edit Program.cs as follows:

Application.Run(new RunFmNet7());

I get this error:

System.IO.FileNotFoundException: 'Could not load file or assembly 'System.Runtime, Version=7.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'

I edit the config but it still is not working:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>

    <runtime>
        <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
            <dependentAssembly>
                <assemblyIdentity name="System.Windows.Forms" culture="neutral" publicKeyToken="b77a5c561934e089"/>
                <bindingRedirect oldVersion="6.0.0.0-7.0.0.0" newVersion="7.0.0.0"/>
                <codeBase version="7.0.0.0" href="bin\Debug\System.Windows.Forms.dll"/>
            </dependentAssembly>
        </assemblyBinding>
    </runtime>
    <startup> 
        
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.2" />
    </startup>
</configuration>

What can I do to make it work?

Solution

.NET has gone under a substantial renaissance. To that effect, .NET Core (and 5.0 and newer) have a new runtime that isn't compatible with the CLR in .NET Framework. You will have to migrate your old code base to the newer .NET runtime - that includes changing the project structure, identifying incompatible dependencies and rebuilding. Microsoft has extensive documentation on the subject.