Question

Every now and then, I bump into syntax that I’ve seen before, but never used. This is one of those times.

Can someone explain the purpose of ‘:this’ or ‘:base’ following a C# constructor method?

For example:

public MyClass(SomeArg arg) : this(new SomethingElse(), arg) { } 

My gut feeling is that it is used to map a default argument onto another constructor method.

Answer 1

You’re basically right. this() calls a constructor on the current instance, base() calls the supertype’s constructor on current instance. They’re generally used to handle constructor overloads so you can add additional options without breaking things out into a separate method.