public string DbTest([FromBody] DbTest req) { var param = new DynamicParameters(); //param.Add("ThirdPartyCode", null, DbType.String); param.AddDynamicParams(new { ThirdPartyCode = default(string) }); var result = _testDb.C_Test("[Back].[s_ThirdParty_Get]", param, CommandType.StoredProcedure); return(JsonConvert.SerializeObject(result)); }