Webpart usage Problems

Download the webpart demo from Microsoft webcast.
After reading the video, I did it myself. When using dropdownlist to change the displaymode of webpartmanage,
The following error occurs:

"/Demowebpart" Application Program Server error.

This page currently disables the specified display mode. Make sure that personalized settings are enabled for the current user.
Parameter Name: Value

Note:An error occurred while executing the current Web request. Check the stack trace information to learn about this error andCodeDetailed information about the cause of the error.

Exception details:System. argumentexception: This page currently disables the specified display mode. Make sure that personalized settings are enabled for the current user.
Parameter Name: Value

Source error:

Row 26: break; Row 27: Case "D": row 28: webpartmanager1.displaymode = webpartmanager. designdisplaymode; row 29: break; row 30: Case "B ":

Source file:E: \ demowebpart \ default. aspx. CSRow:28

Open the downloaded demo with vs2005 and run it after modifying the database connection of Web. config. The same error is reported, which was found at Google,
One person has encountered such a problem, but no one can solve it after it is sent. I want to send it to the garden to see if any of my friends have met and solved it.

The error code returned when running is as follows (in red ):

Protected void dropdownlistincluselectedindexchanged (Object sender, eventargs E)
{
Switch (dropdownlist1.selectedvalue)
{
Case "C ":
Webpartmanager1.displaymode = webpartmanager. catalogdisplaymode ;
Break;
Case "E ":
Webpartmanager1.displaymode = webpartmanager. editdisplaymode;
Break;
Case "D ":
Webpartmanager1.displaymode = webpartmanager. designdisplaymode;
Break;
Case "B ":
Webpartmanager1.displaymode = webpartmanager. browsedisplaymode;
Break;
Default:
Webpartmanager1.displaymode = webpartmanager. browsedisplaymode;
Break;
}
}
Appendix: Demo http://files.cnblogs.com/szflying/DemoWebPart.rar downloaded from webcast