这是我要序列化/反序列化的类。publicclassMyDic{...[XmlElement(IsNullable=true)]publicListWebDefinitions;...}它是结构WebDefinition的完整定义。publicstructWebDefinition{publicstringDefinition;publicstringURL;publicWebDefinition(stringdef,stringurl){Definition=def;URL=url;}publicoverridestringToString(){returnthis.Definiti

exist用法示例：selectA.IsNullableattrfromUM_M_TableColumnAwhereEXISTS(selectidfromUM_METADATAwhereTENANT_CODE='META2021')groupbyA.IsNullable;--510msin用法示例：selectA.IsNullableattrfromUM_M_TableColumnAwheremeta_data_idIN(selectidfromUM_METADATAwhereTENANT_CODE='META2021')groupbyA.IsNullable;--3.3s关联用法：selec

exist用法示例：selectA.IsNullableattrfromUM_M_TableColumnAwhereEXISTS(selectidfromUM_METADATAwhereTENANT_CODE='META2021')groupbyA.IsNullable;--510msin用法示例：selectA.IsNullableattrfromUM_M_TableColumnAwheremeta_data_idIN(selectidfromUM_METADATAwhereTENANT_CODE='META2021')groupbyA.IsNullable;--3.3s关联用法：selec