need to help retrieve numeric values with dot

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
using System.Text.RegularExpressions;

namespace CLRPlay
{
    public partial class UserDefinedFunctions
    {
	static readonly Regex _regex = new Regex(@"[^0-9]*", RegexOptions.Compiled);
        static readonly string _nR = @"";
       
        [Microsoft.SqlServer.Server.SqlFunction]
        public static SqlString Indexkey(SqlString val)
        {
            if (val.IsNull) return SqlString.Null;
            return _regex.Replace(val.ToString(), _nR);
        }
    };
}