在构造函数C＃中使用静态只读字段

Question

下面是我的类，带有静态只读字段：

public class Stats
{
    public static readonly int MinPoints = 900;
    public static readonly int MaxPoints = 1500;

    public int Points { get; }

    private Stats()
    {
    }

    public Stats(int points) : this()
    {
        if (points < Stats.MinPoints || points > Stats.MaxPoints)
        {
            throw new InvalidOperationException();
        }

        Points = points;
    }
}

编译时，我没有任何错误。但是，当我尝试实例化Stats对象时，却得到了TypeInitializationException。当用适当的值替换构造函数中的PlayerStatistics.MaxPoints时，代码将起作用。

这是单元测试构造函数时出现的错误：

Expected a <System.InvalidOperationException> to be thrown, but found <System.TypeInitializationException>: "
"System.TypeInitializationException with message "The type initializer for 'League.Domain.Player.Stats' threw an exception."
     at League.Domain.Player.Stats..ctor(Int32 points) in C:\dev\repos\League\League.Domain\Player\Stats.cs:line 24
     at League.Tests.StatsSpecs.<>c__DisplayClass1_0.<Create_stats_with_incorrect_points_should_throw_exception>b__0() in C:\dev\repos\League\League.Tests\StatsSpecs.cs:line 36
     at FluentAssertions.Specialized.ActionAssertions.InvokeSubject()
     at FluentAssertions.Specialized.DelegateAssertions`1.InvokeSubjectWithInterception()
.
   at FluentAssertions.Execution.XUnit2TestFramework.Throw(String message)
   at FluentAssertions.Execution.TestFrameworkProvider.Throw(String message)
   at FluentAssertions.Execution.DefaultAssertionStrategy.HandleFailure(String message)
   at FluentAssertions.Execution.AssertionScope.FailWith(Func`1 failReasonFunc)
   at FluentAssertions.Execution.AssertionScope.FailWith(Func`1 failReasonFunc)
   at FluentAssertions.Execution.AssertionScope.FailWith(String message, Object[] args)
   at FluentAssertions.Specialized.DelegateAssertions`1.Throw[TException](Exception exception, String because, Object[] becauseArgs)
   at FluentAssertions.Specialized.DelegateAssertions`1.Throw[TException](String because, Object[] becauseArgs)
   at League.Tests.StatsSpecs.Create_stats_with_incorrect_points_should_throw_exception(Int32 points) in C:\dev\repos\League\League.Tests\StatsSpecs.cs:line 38

这是我的单元测试，用XUnit编写：

[Theory]
[InlineData(899)]
[InlineData(1501)]
public void Create_stats_with_incorrect_points_should_throw_exception(int points)
{
    Action action = () => new Stats(points);

    action.Should().Throw<InvalidOperationException>();
}

有没有办法在构造函数中仍然使用静态只读字段？

Answer 1

我能够找到解决方案...

我试图简化我的代码，而在类中省略一行：

public class Stats
{
    // I didn't put this line of code, so it was working without it
    public static readonly Stats New = new Stats(1000);

    public static readonly int MinPoints = 900;
    public static readonly int MaxPoints = 1500;

    public int Points { get; }

    private Stats()
    {
    }

    public Stats(int points) : this()
    {
        if (points < Stats.MinPoints || points > Stats.MaxPoints)
        {
            throw new InvalidOperationException();
        }

        Points = points;
    }
}

因此，如Dmitry Bychenko所述，在编译时不会分配静态只读字段。因此，如果我将这些行放在我省略的行之前，就像这样：

public static readonly int MinPoints = 900;
public static readonly int MaxPoints = 1500;

public static readonly Stats New = new Stats(1000);

会很好。

感谢他的评论，使用const代替静态的readonly字段使我的代码在任何地方都可以将这两个常量放在我的类中。