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Adds or moves columns to the beginning of an existing table.
Client applications and service providers
The properties passed to HrAddColumnsEx using the lpproptagColumnsNew parameter become the first properties exposed on subsequent calls to the IMAPITable::QueryRows method. Any properties previously in the table that were not specified in the lpproptagColumnsNew parameter are exposed after all the added and moved properties.
If any table properties are undefined when QueryRows is called, they are returned with property type PT_NULL and property identifier PROP_ID_NULL.
The HrAddColumnsEx function allows the caller to furnish a callback function to filter the columns that were already in the table, for example to convert strings from property type PT_UNICODE to PT_STRING8. HrAddColumnsEx passes a pointer to the previously existing column set as the parameter to the callback function. The callback function can change data in the property tag array but cannot add new tags.
HrAddColumnsEx first calls the callback function if one is furnished, then adds or moves the specified columns, and finally calls IMAPITable::SetColumns.
The lpAllocateBuffer and lpFreeBuffer input parameters point to the MAPIAllocateBuffer and MAPIFreeBuffer functions, respectively. The exact values of the pointers passed to HrAddColumnsEx depend on whether the caller is a client application or a service provider. A client passes pointers to the MAPI functions with the specified names. A service provider passes the pointers it received in its initialization call or retrieved by calling the IMAPISupport::GetMemAllocRoutines method.