If you know the borrowing date, you can calculate the return date, and when users borrow books, you can limit it. As for borrowing at most three books, you just add a judgment to judge whether the number of books submitted by users is greater than three, and if so, give a prompt;

DateTime DateNow = date time. Now; //Get the current system time;

Date time date = date time. parse(" 20 14- 10-0 1 ")； //Borrowing time; If it is DateTime data, no conversion is needed;

//Judge whether the number of days minus the borrowing time from the current time is more than 60 days;

If (DateNow. Subtract (date). Duration (). Day & gt60)

{

MessageBox。 Show ("borrowing time exceeds 60 days");

}