IDbCommand PrepareCommand(string cmdText, DbParam[] parameters, CommandType cmdType, out List <OutputParameter> outputParameters) { outputParameters = null; IDbCommand cmd = this._dbConnection.CreateCommand(); cmd.CommandText = cmdText; cmd.CommandType = cmdType; cmd.CommandTimeout = this._commandTimeout; if (this.IsInTransaction) { cmd.Transaction = this._dbTransaction; } if (parameters != null) { for (int i = 0; i < parameters.Length; i++) { DbParam param = parameters[i]; if (param == null) { continue; } if (param.ExplicitParameter != null)/* 如果存在创建好了的 IDbDataParameter,则直接用它。同时也忽视了 DbParam 的其他属性 */ { cmd.Parameters.Add(param.ExplicitParameter); continue; } Type parameterType; if (param.Value == null || param.Value == DBNull.Value) { parameterType = param.Type ?? typeof(object); } else { parameterType = param.Value.GetType(); if (parameterType.IsEnum) { parameterType = Enum.GetUnderlyingType(parameterType); } } IDbDataParameter parameter = null; MappingTypeInfo mappingTypeInfo = MappingTypeSystem.GetMappingTypeInfo(parameterType); if (mappingTypeInfo != null && mappingTypeInfo.MappingType != null) { parameter = mappingTypeInfo.MappingType.CreateDataParameter(cmd, param); } else { parameter = this.CreateDataParameter(cmd, param, mappingTypeInfo); } cmd.Parameters.Add(parameter); OutputParameter outputParameter = null; if (param.Direction == ParamDirection.Output || param.Direction == ParamDirection.InputOutput) { outputParameter = new OutputParameter(param, parameter); if (outputParameters == null) { outputParameters = new List <OutputParameter>(); } outputParameters.Add(outputParameter); } } } return(cmd); }