User defined compiler warning or error in C# [duplicate]

Question

Is it possible to have some code let the compiler generate a compile warning or error?

Maybe with Attributes?

** Having the first answer and a few comments I realize my question is not as a clear as I expected and wanted it to be. I apologize. Hopefully all contributers are still with us.
**

So I am more looking towards an internal DSL.

S.Th. like

[MustAssign]
public string Val {get; set;]

Answer 1

Do you mean #warning ?

#warning lets you generate a level one warning from a specific location in your code. For example:

#warning Deprecated code in this method.

And for errors, there is (you would never guess), #error.