'partial' keyword in C# is very good for project ,what's the same thing in D?

[FrankLike via Digitalmars-d]

Hello,everyone,
I've written some projects  in  C#,find the 'partial' keyword is 
very userful,which lets the auto codes in another single file,my 
codes are very easy to update.
But  what the same thing in D?

Thank you,every one.