Assign multiple values of the structure in C#

Question

Suppose I have the following structure in C#

public struct User
{
    public string name;
    public int ID;
    public bool isAlive;
}

and I want to assign all the values for this structure. The only way I know how to do this is through

User Bill;
Bill.ID = 1;
Bill.name = "Bill";
Bill.isAlive = false;

But is there a faster way to do this? Something like

User Bill = {
  ID : 1,
  name : "Bill",
  isAlive : false
};

See http://stackoverflow.com/questions/740658/whats-the-difference-between-an-object-initializer-and-a-constructor — Chris Laplante, Oct 23 '13 at 22:38
@Servy - well, C# is evil, sou you should not use it. The same is true for PHP, Java, C and everything that is NOT either PHP, Java, C or C#. Must be true - I read each of these on the internet. — Eugen Rieck, Oct 23 '13 at 22:43
@SalvadorDali There are many, many situations in which having mutable structs allows for highly confusing code that is very hard to reason about, ranging from very common cases, often involving mutating a copy of a value type without realizing it, to more obscure cases. You really need to be very intimately familiar with the language and how it functions to really confidently use a mutable value type safely, and those who have such knowledge know enough to know that it's not worth the mental effort unless it's really needed. — Servy, Oct 23 '13 at 22:46
@SalvadorDali Your type also doesn't logically represent a single value, is not a particularly small size, isn't immutable, etc. so it really shouldn't be a value type from a conceptual point of view. — Servy, Oct 23 '13 at 22:47
@EugenRieck That is correct. You should use none of those things. It's machine code or bust. — Servy, Oct 23 '13 at 22:48
Put another way, why is `User` a struct and not a class? There are plenty of good arguments as to why, based on what you've shown here, this should be a class, http://programmers.stackexchange.com/questions/92339/when-do-you-use-a-struct-instead-of-a-class for example. — Preston Guillot, Oct 23 '13 at 22:57
I guess the word *faster* in this context means simpler and less statements. — Ken Kin, Oct 23 '13 at 23:30
The fundamental question that should be asked in selecting between a struct and a class is whether the data type is supposed to represent a user, or whether it's supposed to represent three values stuck together with duct tape. If the former, it should be a mutable class. If the latter, it should be an immutable class or an exposed-field structure. — supercat, Oct 24 '13 at 04:58
@Servy: If instances of a data type shouldn't have a persistent identity, the fact that it *doesn't* represent a single unified entity [e.g. a `PointF` represents two `float` values which, though related, are independent] is an argument *in favor* of using an exposed-field struct. I'm not saying the poster's proposed struct is a good one, but mutable class objects should be avoided for things that shouldn't have a composite identity, and immutable types avoided for things which may need to be partially modified. — supercat, Oct 24 '13 at 05:09

score 3 · Accepted Answer · answered Oct 23 '13 at 22:37

3

Yes.

User bill = new User{
  ID = 1,
  name = "Bill",
  isAlive = false
};

answered Oct 23 '13 at 22:37

NomadTraveler

1,086
1
12
37

score 3 · Answer 2 · answered Oct 23 '13 at 22:40

Make a constructor for your struct :

public struct User
{
    public string name;
    public int ID;
    public bool isAlive;

    public User(string name, int ID, bool isAlive)
    {
        this.name = name;
        this.ID = ID;
        this.isAlive = isAlive;
    }
}

Then use it for initialization :

User bill = new User("Bill", 1, false);

score 1 · Answer 3 · answered Oct 23 '13 at 22:38

1

Structs behave exactly like classes (just that they are a value type), so you could - for instance - use constructors and methods.

answered Oct 23 '13 at 22:38

Aurelia

1,052
6
28

Structs and classes are fundamentally different. The notion that they should be expected to work the same is responsible for some people's condemnation of mutable struct semantics, when it is the notion that everything should behave like a class object which is fundamentally wrong. – supercat Oct 24 '13 at 04:56

score 1 · Answer 4 · answered Oct 23 '13 at 22:40

While @Somya's answer is correct and works, I tend not to use this construct. IMHO the correct way to do this is to create a constructor for User, that takes the needed parameters, then call new User (1, "Bill", false).

This could easily be considered a spleen.

score 0 · Answer 5 · answered Oct 23 '13 at 23:11

Suppose you don't have that structure .. you can use anonymous type:

var Bill=new {
    ID=1,
    name="Bill",
    isAlive=false
};

var Gates=new {
    ID=2,
    name="Gates",
    isAlive=true
};

Note the remarks:

If two or more anonymous object initializers in an assembly specify a sequence of properties that are in the same order and that have the same names and types, the compiler treats the objects as instances of the same type. They share the same compiler-generated type information.

Structures are immutable, but an instances of anonymous type is read-only once it's assigned:

Anonymous types provide a convenient way to encapsulate a set of read-only properties into a single object without having to explicitly define a type first. The type name is generated by the compiler and is not available at the source code level. The type of each property is inferred by the compiler.

So you gained both of the benefits with anonymous types.

Assign multiple values of the structure in C#

5 Answers5