Instantiate a List inside of type initializer

Question

Say I have a struct like so

public struct MyStruct
{
     string StructConfig { get; set; }
     List<string> Details { get; set; }

     public MyStruct
     {
         Details = new List<string>();
     }
}

And I instantiate this struct using:

MyStruct s = new MyStruct() 
{
    StructConfig = "Some config details"
}

I'm wondering how I could add a foreach loop that will add the details into the Details property, rather than doing:

MyStruct s = new MyStruct() 
{
    StructConfig = "Some config details"
}
s.Details = new List<string>();
foreach (var detail in someArray)
    s.Details.Add(detail);

Is this even possible? Am I dreaming of code-luxury?

Answer 1

You can do it like this:

MyStruct s = new MyStruct() 
{
    StructConfig = "Some config details",
    Details = new List<string>(someArray)
}

This works because List<T> supports initialization from IEnumerable<T> through this constructor.

If you need to do additional preparations on the elements of someArray, you could use LINQ and add a Select. The example below adds single quotes around each element:

Details = new List<string>(someArray.Select(s => string.Format("'{0}'", s)))

Answer 2

How about?

s.Details = new List<string>(someArray);

Answer 3

Assuming that you don't want to initialize the list from an array but really want to be able to write the list elements directly in your initializer you can use a collection initializer:

var myStruct = new MyStruct() {
  StructConfig = "Some config details",
  Details = new List<string>() { "a", "b", "c" }
};

^{Now, having a struct containing a string and a list of strings looks slightly weird but that doesn't affect how to answer the question.}

Answer 4

can do something like this

MyStruct s = new MyStruct
{
    StructConfig = "Some config details",
    Details = someArray.ToList()
};

Answer 5

You could call the extension method ToList() on the "someArray" collection, which will create a copy of it that you could assign to your struct property, like so:

MyStruct s = new MyStruct() 
{
    StructConfig = "Some config details",
    Details = someArray.ToList()
}

Answer 6

Something along the lines of:

s.Details = someArray.Select(detail=> detail.ToString()).ToList()

Would prevent an exception being thrown were your array not a string[]. Of course, you may wish for the exception to be thrown in this case.

Also, it's worth considering why you are using a struct with a property that is a List; it may be better to have a class instead of a struct.