IbsQueryBuilder Abstract Class that Mimics Laravel ORM for IBS Gateway Builder

IbsQueryBuilder.cs

using System;
using System.Text.RegularExpressions;

namespace ConsoleNancySelfHostedNetTest
{
    public abstract class IbsQueryBuilder
    {
        private string _queryCriteria = "";

        public virtual IbsQueryBuilder Where(string col, string arg1, string arg2 = null)
        {
            string op = "=";
            string value = "";

            if (!string.IsNullOrWhiteSpace(arg2))
            {
                op = arg1;
                value = arg2;
            }
            else
            {
                // only 2 args is present then use = as default operator
                value = arg1;
            }

            // format properly strings or characters
            value = IsNumber(value) ? value : $"[{value}]";

            if (string.IsNullOrWhiteSpace(_queryCriteria))
            {
                _queryCriteria = $"{col}{op}{value}";
            }
            else
            {
                _queryCriteria += $" and {col}{op}{value}";
            }

            return this;
        }

        public virtual IbsQueryBuilder OrWhere(string col, string arg1, string arg2 = null)
        {
            string op = "=";
            string value = "";

            if (!string.IsNullOrWhiteSpace(arg2))
            {
                op = arg1;
                value = arg2;
            }
            else
            {
                // only 2 args is present then use = as default operator
                value = arg1;
            }

            // format properly strings or characters
            value = IsNumber(value) ? value : $"[{value}]";

            if (string.IsNullOrWhiteSpace(_queryCriteria))
            {
                _queryCriteria = $"{col}{op}{value}";
            }
            else
            {
                _queryCriteria += $" or {col}{op}{value}";
            }

            return this;
        }

        public virtual IbsQueryBuilder WhereRaw(string criteria)
        {
            return SetRawCriteria("and", criteria);
        }

        public virtual IbsQueryBuilder OrWhereRaw(string criteria)
        {
            return SetRawCriteria("or", criteria);
        }

        private IbsQueryBuilder SetRawCriteria(string comparator, string criteria)
        {
            if (string.IsNullOrWhiteSpace(_queryCriteria))
            {
                _queryCriteria = criteria;
            }
            else
            {
                _queryCriteria += $" {comparator} {criteria}";
            }

            return this;
        }

        private Boolean IsNumber(string input)
        {
            return Regex.IsMatch(input, @"^\d+$");
        }

        public IbsQueryBuilder ClearQuery()
        {
            _queryCriteria = "";

            return this;
        }

        public string ToQuery()
        {
            string temp = _queryCriteria;

            // clear this property since at this point we already built the query
            ClearQuery();

            return temp;
        }
    }
}