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Tuesday, January 6, 2009

VB Hangs While Automating Excel Using OLE Control

In this addition i am describe Microsoft excel support to fix when excel using OLE control and VB hangs.This problem occurs while automating an Excel object that is using in-place activation in an OLE control. The problem does not occur with all methods or properties. This problem has been reported with the following method/properties in the Microsoft Excel object library:

PrintOut
Delete
Dialog.Show


A workaround is to not activate the object while running the automation code. However, if you need to activate the object, do so in a separate window instead of using in-place activation. For example, this line activates the object in a separate window:

OLE1.DoVerb vbOLEOpen


Another workaround is to deactivate the object before calling the automation code that causes Visual Basic to hang. For example, the PrintOut and Delete methods cause this problem to occur. Before using these methods, you can deactivate the object prior to calling the method, then optionally reactivate the object after calling the method. See the MORE INFORMATION section later in this article for an example.


Steps to Reproduce Behavior

1. Start a new Standard EXE project in Visual Basic. Form1 is created by default.
2. On the Project menu, click References, and then select the Microsoft Excel 8.0 object library. For Excel 2000, select the version 9.0 object library.
3. Place an OLE control on Form1 and create a new Microsoft Excel worksheet. The OLE control properties should be:


Property Value
Name OLE1
Class Excel.Sheet.8
4. Place a CommandButton on Form1.
5. Copy the following code to the Code Window of Form1:

Private Sub Command1_Click()
Dim xlBook As Excel.Workbook
Set xlBook = OLE1.object
OLE1.DoVerb vbOLEShow 'or OLE1.DoVerb vbOLEUIActivate
xlBook.Worksheets("Sheet1").Range("A1").Value = "Hello"
xlBook.Worksheets("Sheet1").PrintOut
Set xlBook = Nothing
End Sub


6. On the Run menu, click Start, or press the F5 key to start the program.
7. Click the CommandButton. Visual Basic hangs after it encounters the PrintOut method. The object will be correctly printed, but Visual Basic stops responding. You must select End Task in the task list (by pressing the CTRL+ALT+DEL keys) to end the Visual Basic project and Excel. Repeat until both Excel and the Visual Basic project are removed from the task list.
8. Repeat the steps again with the code modified as follows:

Private Sub Command1_Click()
Dim xlBook As Excel.Workbook
Set xlBook = OLE1.object
OLE1.DoVerb vbOLEShow 'or OLE1.DoVerb vbOLEUIActivate
xlBook.Worksheets("Sheet1").Range("A1").Value = "Hello"
Command1.SetFocus 'causes deactivation of object
xlBook.Worksheets("Sheet1").PrintOut
OLE1.DoVerb vbOLEShow 'optional: reactivates object
Set xlBook = Nothing
End Sub


The problem is avoided by deactivating the object before calling the PrintOut method. Setting focus to any control on the form will deactivate the OLE control object.
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