C#•11mo ago

C++ struct initializing in C#

in C++, we can do this -

struct Foo
{
  int A;
  int B;
};
Foo a = { 5, 7 };
std::cout << a.A; // 5
std::cout << a.B; // 7

struct Foo
{
  int A;
  int B;
};
Foo a = { 5, 7 };
std::cout << a.A; // 5
std::cout << a.B; // 7

But I found that I can't do this in C#. Do I have to assign values by each one like this?

a.A = 5;
a.B = 7;

a.A = 5;
a.B = 7;

I want to know how to assign member values simply in C#.

7 Replies

TheRanger•11mo ago

Foo a = new Foo{ A = 5, B = 7 }; however you can do Foo a = (5, 7); if you defined an implicit operator that has a parameter of a specific ValueTuple

yzOP•11mo ago

So I have to make an operator if I don't want new?

MODiX•11mo ago

TheRanger

REPL Result: Success

struct Foo
{
  public int A;
  public int B;
    
    public static implicit operator Foo((int a, int b) v)
    {
        return new Foo{ A = v.a, B = v.b };
    }
};

        Foo a = (5,7);
        Console.WriteLine($"{a.A} {a.B}");

struct Foo
{
  public int A;
  public int B;
    
    public static implicit operator Foo((int a, int b) v)
    {
        return new Foo{ A = v.a, B = v.b };
    }
};

        Foo a = (5,7);
        Console.WriteLine($"{a.A} {a.B}");

Console Output

5 7

5 7

Compile: 530.825ms | Execution: 42.423ms | React with ❌ to remove this embed.

TheRanger•11mo ago

yes C# probably didnt allow this syntax Foo a = { 5, 7 }; due to safety reasons

yzOP•11mo ago

I see Thanks!

sibber•11mo ago

Foo a = new() { A = 5, B = 7 };

Foo a = new() { A = 5, B = 7 };

is also valid

Jester•11mo ago

i think new struct means that it gets allocated on the heap in c++? in c# thats not always the case. it allocates on the stack in your method but ofc if you assign it to a field in a class which is on the heap then its on the heap but thats the same as in c++

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C++ struct initializing in C#