怎么说C＃中的数字是长或小数？

Question

You can specify that a number is a double using the below code ('d' letter):

 double hi = 12d;

How to say a number is a long or decimal?

decimal dcml = 12?;
long lng = 12?;

Answer 1

The type suffix for long is L
The type suffix for decimal is M

decimal dcml = 12M;
long lng = 12L;

This is a simple article as a reference (simple meaning easier to read and digest, not simplistic)
This is the reference for integers and for real numbers from the C# Language Specifications

Answer 2

Like this

decimal dcml = 12M;
long lng = 12L;