How to use the source generators from CommunityToolkit.Mvvm for a .NET Framework 4.7.2 WPF Application

Question

I recently tested the WPF UI library ( https://wpfui.lepo.co/ ). I created a sample project, and that project targeted .NET 6.0. The sample project contained some basic Models and ViewModels, and in those files I found properties declared using the [ObservableProperty] attribute. I really liked how that reduced the amount of code needed for simple properties, so I wanted to use that for an existing project which targets .NET Framework 4.7.2.

But I don't know how or if it is even possible. Existing information that I find online is very confusing, but the accepted answer to this question sounds like it is possible: Roslyn Source Generator not generating any source in a .net framework 4.7.2

I tried the following, but the application won't build:

using CommunityToolkit.Mvvm.ComponentModel;

namespace MatlogUtility
{
    public partial class HeatListEntry : ObservableObject
    {
        [ObservableProperty]
        private int? heatListId;

    }
}

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Threading.Tasks;
using System.Windows;
using MatlogUtility.Models;


namespace MatlogUtility
{
    public static class SqlQueries
    {
        public static List<HeatListEntry> GetHeatList()
        {
            List<HeatListEntry> heatList = new List<HeatListEntry>();

            string queryString = "SELECT a as heatListId FROM someTable;";

            using (SqlConnection connection = new SqlConnection(Globals.ConnectionString))
            {
                SqlCommand command = new SqlCommand(queryString, connection);
                connection.Open();
                var reader = command.ExecuteReader();
                try
                {
                    while (reader.Read())
                    {
                        heatList.Add(new HeatListEntry
                        {
                            HeatListId = reader["heatListId"] == DBNull.Value ? null : (int?)reader["heatListId"]
                        });
                    }
                }
                finally
                {
                    // Always call Close when done reading.
                    reader.Close();
                }
            }

            return heatList;
        }
    }
}

The error list shows that 'HeatListEntry' does not contain a definition for HeatListId'

I also tried installing a bunch of NuGet-packages related to 'Roslyn', for example Microsoft.CodeAnalysis.CSharp and Microsoft.CSharp, but it still doesn't work.

Is what I am trying to do even possible? Thanks in advance, any pointers are appreciated!

Answer 1

I also got into the same issue. It seems MVVM Source Generators don't support older .net frameworks (till 4.8). I changed my project framework from 4.8 to .net 6 and it worked fine.
You can also try, Upgrade a WPF App to .NET 6 with the .NET Upgrade Assistant

Answer 2

Worked with CommunityToolkit.Mvvm 8.0.0 for me in .NET 4.8:

1. Right click the packages.config-File.
2. Choose "Migrate packages.config to PackageReference..."

Also, you need to set the LangVersion to a minimum of 8.0