How do you declare a class in C#?

A class is an abstract representation for some particular type of object. It can be described as a template or blueprint for an object, as opposed to the actual object itself.

[attributes] [modifiers] class identifier [:base-type]
{
  body [;]

}

Reference Link :- Declaring Classes[^]
In addition to this you can get plenty of article after googling for same question.
Link1[^]
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Link3-[How to Create Class][^]
Link4-[Introduction to Class][^]