My.Application.DoEvents Method
Processes all Windows messages currently in the message queue.
' Usage
My.Application.DoEvents()
' Declaration
Public Sub DoEvents()
Remarks
The My.Application.DoEvents method allows your application to handle other events that might be raised while you code runs. The My.Application.DoEvents method has the same behavior as the DoEvents method.
When you run a Windows Forms application, it creates a new form, which then waits for events to be handled. Each time the form handles an event, such as a button click, it processes all the code associated with that event. All other events wait in the queue. While your code handles the event, your application does not respond. For example, the window does not repaint if another window is dragged on top.
If you call My.Application.DoEvents in your code, your application can handle the other events. For example, if your code adds data to a ListBox in a loop, and after each step of the loop it calls My.Application.DoEvents, your form repaints when another window is dragged over it. If you remove My.Application.DoEvents from your code, your form will not repaint until the click event handler of the button is finished executing.
Typically, you use this method in a loop to process messages.
Note
The My.Application.DoEvents method does not process events in exactly the same way as the form does. Use multithreading to make the form directly handle the events. For more information, see Multithreading in Visual Basic.
Warning
If a method that handles a user interface (UI) event calls the My.Application.DoEvents method, the method might be re-entered before it finishes. This can happen because the My.Application.DoEvents method processes Windows messages, and Windows messages can raise events.
Tasks
The following table lists an example of a task involving the My.Application.DoEvents method.
To |
See |
|---|---|
Allow a form to respond to UI input while busy |
Example
This example uses the My.Application.DoEvents method to allow the UI for TextBox1 to update.
Private Sub TestDoEvents()
For i As Integer = 0 To 10000
TextBox1.Text = i.ToString
My.Application.DoEvents()
Next
End Sub
This code should be in a form that has a TextBox1 component with a Text property.
Requirements
Namespace:Microsoft.VisualBasic.ApplicationServices
Class:WindowsFormsApplicationBase
Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)
Availability by Project Type
Project type |
Available |
|---|---|
Windows Application |
Yes |
Class Library |
No |
Console Application |
No |
Windows Control Library |
No |
Web Control Library |
No |
Windows Service |
No |
Web Site |
No |
Permissions
The following permissions may be necessary:
Permission |
Description |
|---|---|
Controls the ability to access files and folders. Associated enumeration: Unrestricted. |
|
Controls the permissions related to user interfaces and the clipboard. Associated enumeration: AllWindows. |
For more information, see Code Access Security and Requesting Permissions.