How to make a default value for the struct in C#?

Question

I'm trying to make default value for my struct. For example default value for Int - 0, for DateTime - 1/1/0001 12:00:00 AM. As known we can't define parameterless constructor in structure.

struct Test {     int num;     string str; }  class Program {     static void Main(string[] args)     {         Console.WriteLine(default(Test)); // shows namespace and name of struct test.Test         Console.WriteLine(new Test()); // same          Console.ReadKey(true);     } } 

How can I make a default value for struct?

Answer 1

You can't. Structures are always pre-zeroed, and there is no guarantee the constructor is ever called (e.g. new MyStruct[10]). If you need default values other than zero, you need to use a class. That's why you can't change the default constructor in the first place (until C# 6) - it never executes.

The closest you can get is by using Nullable fields, and interpreting them to have some default value if they are null through a property:

public struct MyStruct {   int? myInt;    public int MyInt { get { return myInt ?? 42; } set { myInt = value; } } } 

myInt is still pre-zeroed, but you interpret the "zero" as your own default value (in this case, 42). Of course, this may be entirely unnecessary overhead :)

As for the Console.WriteLine, it simply calls the virtual ToString. You can change it to return it whatever you want.