❔ Need help with discord command to toggle a task

using DSharpPlus;
using DSharpPlus.Entities;
using DSharpPlus.EventArgs;
using DSharpPlus.SlashCommands;

namespace self_bot.commands
{
    internal class TestCommand : ApplicationCommandModule
    {
        private DiscordClient _clientInstance;

        public TestCommand(DiscordClient client)
        {
            _clientInstance = client;
        }

        private static bool IsOn = false;

        [SlashCommand("ToggleTest", "Toggle test messages to be sent at user after every message")]
        public async Task Toggle(InteractionContext ctx, [Option("user", "Specified user")] DiscordUser user)
        {
            IsOn=!IsOn;

            if (IsOn==true)
            {
                await ctx.CreateResponseAsync(InteractionResponseType.ChannelMessageWithSource, new DiscordInteractionResponseBuilder().WithContent("Test toggle online"));
                _clientInstance.MessageCreated += TestMessage(user, e);
            }

            if (IsOn==false)
            {
                await ctx.CreateResponseAsync(InteractionResponseType.ChannelMessageWithSource, new DiscordInteractionResponseBuilder().WithContent("Test toggle shutting down"));
                _clientInstance.MessageCreated -= TestMessage(user, e);
            }
        }
        public async Task TestMessage(DiscordUser user, MessageCreateEventArgs e)
        {
            if (e.Message.Author.Id == user.Id)
            {
                await e.Message.RespondAsync("Test success");
            }
        }
    }
}