What Chao Ge said

During statistics, values are transferred from one page to another. Because Ajax exists, the second page needs to go through page_load twice, the headache is that the value sent from the first page cannot be obtained for the second time.

Super brother said: When Ajax requests to the server, there is no page refresh, and there are random parameters, the server considers it to be two pages. Therefore, if the parameter value passed for the first time is not included, it will not be displayed, because it is considered to be two different pages, the label is a client control, viewstate can also be stored on the client, the server side has not passed the value, so it will not be obtained, the session is the entire lifecycle. You can obtain the value in it unless it is released or exceeds the lifecycle.

I hope I understand it!