What does default(object); do in C#?

Question

Googling is only coming up with the keyword, but I stumbled across some code that says

MyVariable = default(MyObject);

and I am wondering

Answer 1

Specifies the default value of the type parameter.This will be null for reference types and zero for value types.

See default

Answer 2

The default keyword returns the "default" or "empty" value for a variable of the requested type.

For all reference types (defined with class, delegate, etc), this is null. For value types (defined with struct, enum, etc) it's an all-zeroes value (for example, int 0, DateTime 0001-01-01 00:00:00, etc).

It's mostly used with generic code that can be applied to both reference and value types, because you can't assign null to a value type variable.

Answer 3

Another good use of default(T) is when compiler can't determine returning type, like in here

class X
{
    public int? P {get; set;}
}

// assigning in code

var x = new X();

// consider coll["key"] returns object boxed value
// data readers is one such case
x.P = myReader["someColumn"] == DbNull.Value ? default(int?) : (int)myReader["someColumn"];