Path, boxing unboxing, file stream, polymorphic

1. Absolute path and relative path absolute path: This file can be found directly on my computer by the given path. Relative path: The path of the file relative to the application. Conclusion: We should try to use relative paths in development.

2, boxing, unboxing: that is, the value type is converted to a reference type. Unboxing: Converts a reference type to a value type. Look at whether the two types have occurred boxing or unpacking, to see whether there is an inheritance relationship between the two types.

3, the process of creating a file stream object is written in the using, it will automatically help us to release the resources occupied by the stream.

4, the means of realizing polymorphism

1), virtual method Step: 1, the method of the parent class is marked as a virtual method, using the keyword virtual, this function can be re-write the quilt class again.

2), abstract class when a method in the parent class does not know how to implement it, consider writing the parent class as an abstract class and writing the method as an abstract method.

Path, boxing unboxing, file stream, polymorphic