从ASP输入到MySQL.净NULL值

所以我试图从asp.net的输入返回一个值。然而问题是，我一直收到null值。但是如果我输入字符串，就好像它是通过查询插入的一样，它工作得很好。

为什么我得到一个空值?

This Works:
 [HttpPost]
        [Route("A3Bans/searchBan")]
        public string oSearchBan(tBan ban)
        {
            {
                tBan bans = new tBan();
                string dbConnection = "datasource=127.0.0.1;port=3306;username=admin;password=00000";
                MySqlConnection conDataBase = new MySqlConnection(dbConnection);
                MySqlDataReader dbReader;
                MySqlCommand selectCommand = new MySqlCommand("SELECT `BanID`, `GUID`, `BanTime`, `Reason`, `BanType`, `Proof` FROM `a3bans`.`bans` WHERE  `GUID`= 'e7af78997ef220a557c97a1a4c11e0c2'", conDataBase);  //@prmGuid, conDataBase); // Returning a null value?!
               // selectCommand.Parameters.AddWithValue("@prmGuid", new tID(ban.GuidOrIP));
                conDataBase.Open();
                dbReader = selectCommand.ExecuteReader();
                try
                {
                    while (dbReader.Read())
                    {
                        tBan searchBan = new tBan();
                        searchBan.BanID = dbReader.GetString("BanID");
                        searchBan.GuidOrIP = dbReader.GetString("GUID");
                        searchBan.BanTime = dbReader.GetString("BanTime");
                        searchBan.BanType = dbReader.GetString("BanType");
                        searchBan.BanReason = dbReader.GetString("Reason");
                        searchBan.BanType = dbReader.GetString("BanType");
                        searchBan.Proof = dbReader.GetString("Proof");
                        bans = searchBan;
                    }
                }
                catch (Exception ex)
                {
                }
                finally
                {
                    dbReader.Close();
                    conDataBase.Close();
                }
                return bans.Proof;
            }
        }

然而，一旦我试图从另一个来源输入它，它是空的。

所以我的问题在这里:

MySqlCommand selectCommand = new MySqlCommand("SELECT `BanID`, `GUID`, `BanTime`, `Reason`, `BanType`, `Proof` FROM `a3bans`.`bans` WHERE  `GUID`= '@prmGuid'", conDataBase); 
selectCommand.Parameters.AddWithValue("@prmGuid", new tID(ban.GuidOrIP));

带构造函数的类这可能是完全错误的。tID

namespace A3Bans.Schemas
{
    public class tID
    {
        public tID(string guidOrIP)
        {
            GuidOrIP = guidOrIP;
        }
        public string GuidOrIP { get; set; }
        public string BanID { get; set; }
    }
}

如果我不得不猜它是我的构造函数…任何想法吗?

编辑

让它部分工作，它只是返回错误的值。

MySqlConnection con = new MySqlConnection(dbConnection);
            MySqlCommand cmd;
            con.Open();
            MySqlDataReader dbReader;
            string cmdText = "SELECT `BanID`, `GUID`, `BanTime`, `Reason`, `BanType`, `Proof` FROM `a3bans`.`bans` WHERE  `GUID` LIKE @pGUID";

            cmd = new MySqlCommand(cmdText, con);
            cmd.Parameters.AddWithValue("@pGUID", "%" + bans.GuidOrIP + "%");

..... WHERE `GUID`= @prmGuid", conDataBase);