help needed ! sql query

my app contains one form (aspx) and it has different controls to be filled by user (textbox,radiobutton ..etc)
it has one button which i want to use to pass values entered in these controls to other page and do some queries to sql server there (2nd page)
Now the thing is ...my controls can have NULL values ...like user could enter just one parameter and hit button
or user can fill 2 parameter and hit enter
so on the other hand (2nd page) how should i query the database accordingly ...

Example:
if (myTextBox.Text == String.Empty)
{
myParameter.Value = DBNull.Value;
}
else
{
myParameter.Value = myTextBox.Text;
}
|||

You can always use an If Else loop to write the query.
If IsDbNull(parameter) Then
parameter = (Whatever default value or just null)
Else
parameter = Request.Form("name of parameter")
End If
I hope this is clear enough.