Chapter 5 - Understanding Partial Classes - 6

The partial keyword allows for a single class to be partitioned across multiple code files. Any code that you have written to augment those files is not overwritten, presuming your code is in separate class files marked with the partial keyword.

Employee.Core.cs

partial class Employee
 {
     // Field Data
   // Constructors
 }

Employee.cs

partial class Employee
 {
     // Methods
    // Properties
 }