UPDATE: Nevermind this doesn’t work. It passes the compiler, but gives a runtime error. Sorry.
Today I found an interesting trick you can do with object initializers that I hadn’t noticed before.
1
2 class MyClass
3 {
4 public int Id { get; set; }
5 public string Description { get; set; }
6 public List<string> FirstList { get; set; }
7 public List<string> SecondList { get; set; }
8 }
9
10 class Program
11 {
12 static void Main(string[] args)
13 {
14 var mc = new MyClass
15 {
16 Id = 1,
17 Description = "One",
18 FirstList = new List<string> { "123", "456" },
19 SecondList = { "123", "456" }
20 };
21
22 // works
23 var l1 = new List<string> { "123", "456" };
24
25 // does not work
26 List<string> l2 = { "123", "456" };
27 }
28 }
29
If you noticed when the list of part of class that uses a setter you can use a short cut and leave out the new List<string> portion. There interesting part is that it doesn’t work by normal assignment as shown on line 26.
The other interesting part is that this works with dictionaries.
1
2 class MyClass
3 {
4 public int Id { get; set; }
5 public string Description { get; set; }
6 public Dictionary<string, int> FirstDictionary { get; set; }
7 public Dictionary<string, int> SecondDictionary { get; set; }
8 }
9
10 class Program
11 {
12 static void Main(string[] args)
13 {
14 var mc = new MyClass
15 {
16 Id = 1,
17 Description = "One",
18 FirstDictionary = new Dictionary<string, int> { { "123", 4 }, { "456", 5 } },
19 SecondDictionary = { { "123", 4 }, { "456", 7 } }
20 };
21
22 // works
23 var d1 = new Dictionary<string,int> { {"123",4}, {"456",7} };
24
25 // does not work
26 Dictionary<string,int> d2 = { {"123",4}, {"456",7} };
27 }
28 }
29
Personally I find this useful while writing unit tests. Quite often I setup objects in a particular state, so any shortcut to make this faster and cleaner is better.
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