Errors assigning config to variables

Code:

using System.Collections.Generic;
using System;
using System.Reflection;
using System.Data;
using UnityEngine;
using Oxide.Core;
using Oxide.Core.Configuration;
using Oxide.Core.Plugins;namespace Oxide.Plugins
{
    [Info("NameRewards", "Kappasaurus", "1.0.0")]
    [Description("Give players permissions based on phrases in their name.")]    class NameRewards : RustPlugin
    {
        string Perm = Config["PermName"].ToString();
        string Phrase = Config["NamePhrase"].ToString();
        void OnPlayerInit(BasePlayer player)
        {
            if (BasePlayer.displayName.Contains(Phrase))
            {
                permission.GrantUserPermission(player.UserIDString, Perm, this);
            }
            else
            {
                permission.RevokeUserPermission(player.UserIDString, Perm, this);
            }
        }        protected override void LoadDefaultConfig()
        {
            PrintWarning("Generating your config file!");
            Config.Clear();
            Config["NamePhrase"] = "";
            Config["PermName"] = "";
            SaveConfig();
        }
    }
}

I keep getting this error, along with the one under.




Can anyone spot the cause of the errors?