MMCN_COLUMNS_CHANGED message
The MMCN_COLUMNS_CHANGED notification is introduced in MMC 1.2.
The MMCN_COLUMNS_CHANGED notification is sent to the snap-in's IComponent::Notify method when the user hides columns or makes columns visible in the list view using the Modify Columns dialog box.
The notification tells the snap-in which columns in the list view are visible. The param parameter passed to the snap-in in the IComponent::Notify method is a pointer to the MMC_VISIBLE_COLUMNS structure that contains the visible columns data.
Parameters
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lpDataObject [in]
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A pointer to the data object of the currently selected scope item.
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arg
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Zero.
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param [in]
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A pointer to an MMC_VISIBLE_COLUMNS structure that contains the list of visible columns.
Return value
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S_OK
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The snap-in accepts user changes to the visible/hidden status of columns in the list view, and MMC will apply these changes by updating the column configuration data of the affected column set.
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S_FALSE
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The snap-in does not handle the notification. MMC then performs a default operation for the notification, which is to apply the changes by updating the column configuration data.
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E_UNEXPECTED
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The snap-in rejects the user changes, and MMC will not apply these changes. Be aware that the snap-in is responsible for informing the user why it is refusing the user changes, for example, by means of a message box.
Remarks
MMC only updates and persists new column configuration data after the snap-in returns S_OK in its MMCN_COLUMNS_CHANGED notification handler. Consequently, if the snap-in queries for persisted column configuration data while handling the notification (before returning S_OK), it will retrieve currently persisted data. This data will not reflect the user changes that resulted in the MMCN_COLUMNS_CHANGED notification message to the snap-in.
The MMCN_COLUMNS_CHANGED notification is particularly useful in situations in which there is a concern about the performance impact of populating data in columns that aren't being displayed. A snap-in can choose to update only visible columns and can use information from MMCN_COLUMNS_CHANGED to do so.
Be aware that the MMCN_COLUMNS_CHANGED notification is not generated for column width changes or sorted column and sort direction changes made by the user or by the snap-in (using the IColumnData::SetColumnConfigData and IColumnData::SetColumnSortData methods).
Also, the MMCN_COLUMNS_CHANGED notification is not generated for any changes made by the snap-in using the IHeaderCtrl2::SetColumnWidth, IHeaderCtrl2::InsertColumn, and IHeaderCtrl2::DeleteColumn methods.
Requirements
| Minimum supported client |
Windows Vista |
| Minimum supported server |
Windows Server 2008 |
| Header |
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