HOWTO: Tell if UserControl is in Design-Time or Run-Time

• Microsoft Visual Basic Control Creation, Professional, and Enterprise Editions for Windows, version 5.0

SUMMARY

When creating a UserControl in Visual Basic you may have code that you don't what to run when the control is on a Form at design-time, but you do want to run when the Form is in run-time. This article shows how to use the AmbientProperties Object to tell when a host container of a control is in design or run-time.

MORE INFORMATION

When a UserControl is placed on a form, any constituent controls that are in the control are in run-time mode, not design-time mode. Usually this does not cause any trouble for the developer. But there are cases where you need to have an event happen only when the container for the UserControl is in run-time. The following example shows how to enable or disable a Timer control by testing to see if the container is in design-time or run-time.

Step-by-Step Example

1. Create a New Standard EXE project.

2. From the Project Menu, select Add UserControl.

3. Add a Timer and a Label control to the UserControl.

4. Add the Following Code to the UserControl:

         Private Sub Timer1_Timer()
            Label1.Caption = Time()
         End Sub
   
         Private Sub UserControl_Show()
            If Ambient.UserMode Then 'We are in run-time
               Timer1.Interval = 1000
               Timer1.Enabled = True
            Else 'We are in design-time
               Timer1.Enabled = False
               Label1.Caption = "design time"
            End If
         End Sub
   
   

5. Close the UserControl.

6. Add the UserControl to Form1.

7. Run the Form.

8. Close the Form.

REFERENCES

Visual Basic Component Tools Guide, Chapter 9.