Hi,
You need to test if
li_Make.Items.FindByText("Maruti Suzuki")
is null before using one of its properties.
If you use an object property and the object is null then it will throw an exception object reference not found.
To avoid throwing the exception you could do a test before using your object, for example in that way:
if (li_Make.Items.FindByText("Maruti Suzuki")!= null)
li_Make.Items.FindByText("Maruti Suzuki").Selected = true;
you can see details about his exception here:
http://msdn.microsoft.com/en-us/library/system.data.objectnotfoundexception.aspx[
^]
Valery.