slarny4/Demo1/Data/Exceptions/GroupNotFoundException.cs

// C:\Users\adm\Source\Repos\presence1\Demo\Data\Exceptions\GroupNotFoundException.cs
using System;

namespace Demo.Data.Exceptions
{
    public class GroupNotFoundException : Exception
    {
        public GroupNotFoundException(int groupId)
            : base($"Group with ID {groupId} was not found.")
        {
        }
    }
}