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copied!<p>It seems to depend on the sequence of lines. This code works:</p> <pre><code>static private List<int> a = new List<int>() { 1 }; static private List<int> b = new List<int>() { a[0] }; </code></pre> <p>while this code does not work (it throws a <code>NullReferenceException</code>)</p> <pre><code>static private List<int> a = new List<int>() { b[0] }; static private List<int> b = new List<int>() { 1 }; </code></pre> <p>So, obviously no rules for cyclical dependency exist. It's peculiar however that the compiler does not complain...</p> <hr> <p>EDIT - What's happening "across files"? If we declare these two classes:</p> <pre><code>public class A { public static List<int> a = new List<int>() { B.b[0] }; } public class B { public static List<int> b = new List<int>() { A.a[0] }; } </code></pre> <p>and try to access them with this code:</p> <pre><code>try { Console.WriteLine(B.b); } catch (Exception e) { Console.WriteLine(e.InnerException.Message.); } try { Console.WriteLine(A.a); } catch (Exception e) { Console.WriteLine(e.InnerException.Message); } try { Console.WriteLine(B.b); } catch (Exception e) { Console.WriteLine(e.InnerException.Message); } </code></pre> <p>we are getting this output:</p> <pre><code>The type initializer for 'A' threw an exception. Object reference not set to an instance of an object. The type initializer for 'A' threw an exception. </code></pre> <p>So the initialization of <code>B</code> causes an exception in static constructor <code>A</code> and lefts field <code>a</code> with the default value (null). Since <code>a</code> is <code>null</code>, <code>b</code> can not also be initialized properly.</p> <p>If we do not have cyclical dependencies, everything works fine.</p> <hr> <p>EDIT: Just in case you didn't read the comments, <a href="https://stackoverflow.com/users/22656/jon-skeet">Jon Skeet</a> provides a very interesting reading: <a href="http://csharpindepth.com/Articles/General/Beforefieldinit.aspx" rel="nofollow noreferrer">The differences between static constructors and type initializers</a>.</p>

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