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ToolStripItem.QueryContinueDrag Event

Occurs during a drag-and-drop operation and allows the drag source to determine whether the drag-and-drop operation should be canceled.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

[BrowsableAttribute(false)]
public event QueryContinueDragEventHandler QueryContinueDrag

The QueryContinueDrag event is raised when there is a change in the keyboard or mouse button state during a drag-and-drop operation. The QueryContinueDrag event allows the drag source to determine whether the drag-and-drop operation should be canceled.

The following remarks describe how and when events related to drag-and-drop operations are raised.

The DoDragDrop method determines the item under the current cursor location. It then checks to see if the item is a valid drop target.

If the item is a valid drop target, the GiveFeedback event is raised with the drag-and-drop effect specified. For a list of drag-and-drop effects, see the DragDropEffects enumeration.

Changes in the mouse cursor position, keyboard state, and mouse button state are tracked in the following manner:

  • If the user moves out of a window, the DragLeave event is raised.

  • If the mouse enters another item, the DragEnter for that control is raised.

  • If the mouse moves but stays within the same item, the DragOver event is raised.

If there is a change in the keyboard or mouse button state, the QueryContinueDrag event is raised and determines whether to continue the drag, to drop the data, or to cancel the operation based on the value of the Action property of the event's QueryContinueDragEventArgs.

If the value of DragAction is Continue, the DragOver event is raised to continue the operation and the GiveFeedback event is raised with the new effect so appropriate visual feedback can be set. For a list of valid drop effects, see the DragDropEffects enumeration.

The DragOver and GiveFeedback events are paired so that as the mouse moves across the drop target, the user is given the most up-to-date feedback on the mouse's position, as follows:

  • If the value of DragAction is Drop, the drop effect value is returned to the source, so the source application can perform the appropriate operation on the source data; for example, cut the data if the operation was a move.

  • If the value of DragAction is Cancel, the DragLeave event is raised.

The following code example demonstrates the use of this member. In the example, an event handler reports on the occurrence of the QueryContinueDrag event. This report helps you to learn when the event occurs and can assist you in debugging. To report on multiple events or on events that occur frequently, consider replacing MessageBox.Show with Console.WriteLine or appending the message to a multiline TextBox.

To run the example code, paste it into a project that contains an instance of a type that inherits from ToolStripItem, such as a ToolStripButton or ToolStripMenuItem. Then name the instance ToolStripItem1 and ensure that the event handler is associated with the QueryContinueDrag event.

private void ToolStripItem1_QueryContinueDrag(Object sender, QueryContinueDragEventArgs e) {

System.Text.StringBuilder messageBoxCS = new System.Text.StringBuilder();
messageBoxCS.AppendFormat("{0} = {1}", "KeyState", e.KeyState );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "EscapePressed", e.EscapePressed );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "Action", e.Action );
messageBoxCS.AppendLine();
MessageBox.Show(messageBoxCS.ToString(), "QueryContinueDrag Event" );
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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