Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
365 views
in Technique[技术] by (71.8m points)

c# - Casting between two types derived from the (same) interface

I have an interface and two types that derive from it.

However, I cannot do the following:

B objectB = (B) objectA

Where B derives from Interface1 (I am making up the name of classes but the point still stands), and likewise for objectA (which is of type A). I get the following error message:

Cannot cast expression of type A to B.

Both types are deriving from the interface, what am I missing?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)
  1. Types do not derive from an interface. They implement an interface.
  2. The fact that both an Elephant and a Spider are Animals doesn't mean that you can convert one to the other.

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...