there are many ways to do that.one of them is as
follows -

You need to check if the value of the checkbox is
set or not by isset function of php.

its a tricky part to create a php multidimensional array
which will be accessed by javascript function.most of the
time it's confusing.i am going to show how to solve the
problem -

in one of my application i had to refresh a page when the page is
loaded from a click command.so i used javascript to do that but i
had to do it from code behind by registering javascript -

there are different kind of joins available by sql like
inner join,left join,etc.by the following example i will show
how to do left join which i used in my application to
get data from two tables -

in some way these codes will help you very much if you need
to know file extension.
method below returns true if extension are any of the following -

It's a very logical requirement to validate user entered email
address before processing anything.in this way you will
never get a invalid email address when you do something
with email address like send email,etc.

using asp.net membership Probvider you can easily
make a user login using username and password and redirect to
default or any page by the following way -

you may want to show smooth jquery popup when user visited
your site or on a button click in any page,etc... from code behind.

i am here sharing codes for showing popup using jquery properly -

following way a DataTable with data can be used to
populate gridview control in asp.net.following codes get files list
from a file path and adds in DataTable then sets that
DataTable as a DataSource of the GridView grdDirList.

using SMO classes one can backup a sql server database
in .bak extension.It's a programming approach to backup
database.there are other ways but using SMO classes it
is efficient and error free.