Error of Webpart
#1. Error shown after add webpart: nullreferenceexception: object reference not set to an instance of an object
Cause :
1. Check the function in cs file if there is any null return.
2. Check variable defined correctly. Eg: checkbox field type is boolean, not string.
#2. Webpart is there but no data shown and no error shown.
Cause: Check logic of ifelse statement.
#3. Webpart for carousel using Owl Carousel, all items appears in 1 row and ignore the option of items.
Cause: The webpart zone is wider the carousel.
Solution: If using with bootstrap theme, webpart zone is in row > col, and webpart for carousel is in container > row (again) > col (again). Weird huh? If it still happen, need to check the styling.
#4. Web Part appears to be causing a problem. Value cannot be null. Parameter name: source
Cause: Field name in Lists related to the webpart is wrong. Or, the Lists have no data.
