When mater page is used in Asp.net 2.0, form defaultbutton cannot be set.

Questions

I tried the following methods on the pageProgramAdd:

1 Protected   Override   Void Oninit (eventargs E)
2 {
3Base. Oninit (E );
4Page. Form. defaultbutton= "Btnsearch";
5}

However, an error is prompted on the page and an error is reported.
 

The defaultbutton of 'form1 'must be the ID of a control of Type ibuttoncontrol.

Description:An unhandled exception occurred during the execution of the current Web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception details:System. invalidoperationexception: The defaultbutton of 'form1 'must be the ID of a control of Type ibuttoncontrol.

Source error:

An unhandled exception was generated during the execution of the current Web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack trace:

Do you know which senior personnel have a good solution?