The type 'CodeActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Activities

Question

im trying to make a simple acivity for uipath in c# , i had used the System.Activties versoin 4.0.0.0

and inside the nuget pakage explorer i had created net461 and net6.0-windows7.0 folders respectedly also in the depenecy section i had added the target framework as the same as the folder names

i dont know why but when im using the activity in windows compatblity (net.6.0 +) project settings in uipath im getting this error

Unexpected error has occurred during the library compilation process:
The assembly compilation returned the following errors:
 * (1,7939): error CS0012: The type 'CodeActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Activities, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.
 * (1,7939): error CS0117: 'ConcatString' does not contain a definition for 'DisplayName'
 * (1,7954): error CS0012: The type 'InArgument<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Activities, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.
 * (1,8181): error CS0012: The type 'OutArgument<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Activities, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.
 * (1,8435): error CS0012: The type 'InArgument<>' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Activities, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.
 * (1,7840): error CS0012: The type 'CodeActivity' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Activities, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.

I dont know what is happening i also had a System.Activties version 6.0.0.0 it works all fine in both windows and windows legacy projects (.net6.0+ and v4.6.1+)

this is the code for the activity

using System.Activities;
using System.ComponentModel;

namespace String_Concatination
{

    public class ConcatString : CodeActivity
    {
        [RequiredArgument]
        [Category("Input")]
        [DisplayName("First String")]
        [Description("Enter First String")]
        public InArgument<string> FirstString { get; set; }

        [RequiredArgument]
        [Category("Input")]
        [DisplayName("Second String")]
        [Description("Enter Second String")]
        public InArgument<string> SecondString { get; set; }

        [Category("Output")]
        [DisplayName("Result")]
        public OutArgument<string> OutputString { get; set; }
        protected override void Execute(CodeActivityContext context)
        {
            var firstString = FirstString.Get(context);
            var secondString = SecondString.Get(context);

            var outString = firstString + secondString;

            OutputString.Set(context,outString);
        }
    }
}

and here is the code of the metadata reference in the NuGet package explorer

<?xml version="1.0" encoding="utf-8"?>
<package xmlns="http://schemas.microsoft.com/packaging/2012/06/nuspec.xsd">
  <metadata>
    <id>ConcatString.Activities</id>
    <version>1.0.5</version>
    <title>ConcatString.Activities</title>
    <authors>Sagar Raval</authors>
    <owners>Feat Systems</owners>
    <requireLicenseAcceptance>false</requireLicenseAcceptance>
    <description>This Activity Helps to Concatinate Two String</description>
    <dependencies>
      <group targetFramework=".NETFramework4.6.1" />
      <group targetFramework="net6.0-windows7.0" />
    </dependencies>
  </metadata>
</package>

im doing a simple string concatenation so i didnt have any dependencies or package , thats the reason in the metadata code you are not able to see any dependencies in there respected target frameworks