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Visual Basic Reference

Visual Studio 6.0

OLEStartDrag Event

See Also    Example    Applies To

Occurs when a component's OLEDrag method is performed, or when a component initiates an OLE drag/drop operation when the OLEDragMode property is set to Automatic.

This event specifies the data formats and drop effects that the source component supports. It can also be used to insert data into the DataObject object.

Syntax

Private Sub object_OLEStartDrag(data As DataObject, allowedeffects As Long)

The OLEStartDrag event syntax has these parts:

Part Description
object An object expression that evaluates to an object in the Applies To list.
data A DataObject object containing formats that the source will provide and, optionally, the data for those formats. If no data is contained in the DataObject, it is provided when the control calls the GetData method. The programmer should provide the values for this parameter in this event. The SetData and Clear methods cannot be used here.
allowedeffects A long integer containing the effects that the source component supports. The possible values are listed in Settings. The programmer should provide the values for this parameter in this event.

Settings

The settings for allowedeffects are:

Constant Value Description
vbDropEffectNone 0 Drop target cannot accept the data.
vbDropEffectCopy 1 Drop results in a copy of data from the source to the target. The original data is unaltered by the drag operation.
vbDropEffectMove 2 Drop results in data being moved from drag source to drop source. The drag source should remove the data from itself after the move.

Remarks

The source component should use the logical Or operator against the supported values and place the result in the allowedeffects parameter. The target component can use this value to determine the appropriate action (and what the appropriate user feedback should be).

The OLEStartDrag event also occurs if the components OLEDragMode property is set to Automatic. This allows you to add formats and data to the DataObject object after the component has done so. You can also override the default behavior of the component by clearing the DataObject object (using the Clear method) and then adding your data and formats.

You may wish to defer putting data into the DataObject object until the target component requests it. This allows the source component to save time by not loading multiple data formats. When the target performs the GetData method on the DataObject, the sources OLESetData event will occur if the requested data is not contained in the DataObject. At this point, the data can be loaded into the DataObject, which will in turn provide the data to the target.

If the user does not load any formats into the DataObject, then the drag/drop operation is canceled.

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