This article is inspired by the fact that the icallbackeventhandler callback event JS has never been successful during development.
Microsoft processes the returned informationCodeIt is function webform_executecallback (callbackobject). If an error occurs in the call background, the first letter of the returned information must be e,
If no error occurs and the first letter is not "S", the returned message must contain one |, | the first digit is a number, the number of characters starting from | will be used as the value of the _ eventvalidation control of the page, and the remaining characters will be used as the return value,
The test shows that if response. Write ("ddddddddd") is used to output data in the Code implementing icallbackeventhandler, the data output from response will be placed at the beginning of the page callback.
Format: Response Data | data to be called back
In this way, webform_executecallback cannot be identified and null is returned.
Conclusion: Avoid using response. Write () when using icallbackeventhandler ()