What is the use of partial class?
a). reduction in file contention in shared development environments. The forms designer and the developer are both trying to change the same file.
b). isolation of low-level details. You don't have to worry about the details of how the individual controls are instantiated and initialized.
c). protection for generated code through changes. You are less likely to change the generated code, and any code that you add will not be in the designer file and is protected.
d). all the above