Custom Acitivity doesn't work


I’m practicing creation of custom activities in UiPath. In this example, I want to write an activity which extracts numbers and spaces only from a given string. I wrote a code in Visual Studio, built it, loaded the .dll file to the NuGet and then added to UiPath. But as the output it gives no result unfortunately. What am I doing wrong?

Here’s the Main.xaml
Main.xaml (7.5 KB)

Here’s the Activity .nupkg
extractNumbersActivities.1.0.1.nupkg (3.9 KB)

Here’s the Visual Studio code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Activities;
using System.ComponentModel;

namespace extractNumbersActivity
    public class extractNumbers : CodeActivity
    public InArgument<string> inputString { get; set; }
    public InArgument<string> outputString { get; set; }

    protected override void Execute(CodeActivityContext context)
        string _inputString = inputString.Get(context);

        string _outputString = "";

        for(int i = 0; i < _inputString.Length; i++)
            if (_inputString[i] >= '0' && _inputString[i] <= '9')
                _outputString += _inputString[i];
                _outputString += ' ';

        outputString.Set(context, _outputString);

This should be OutArgument

    public InArgument<string> outputString { get; set; }

Yeah, thank you so much. What a stupid mistake!