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
190 views
in Technique[技术] by (71.8m points)

c# - What's wrong with casting 0.0 to double?

I have InvalidCastException when I try to cast 0.0 to double, why is that so? It's fine when I do (float)value instead.

alt text

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)

In general, when you put a value type into an object (called boxing) you need to unbox it to the exact same value type. You cannot do a conversion to another type instead. This is what happens here.

If you really want to convert the object, you first need to unbox it. Say your original value was a float before you boxed it in an object:

double d = (double) (float) value;

Or use the method proposed by others, which uses Convert. This has the advantage that the original type doesn’t have to be known.


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

...