CodeContracts：ccrewrite失败，Object引用未设置为对象的实例

Question

以下代码使ccrewrite爆炸！想法？ 顺便说一句，如果你注释掉ActualClass，ccrewrite会成功......

    [ContractClass(typeof(TestContracts))]
    interface ITestInterface
    {
        bool IsStarted { get; set; }
        void Begin();
    }

    class ActualClass : ITestInterface
    {
        public bool IsStarted { get; set; }
        public void Begin()
        {
            this.IsStarted = true;
        }
    }

    [ContractClassFor(typeof(ITestInterface))]
    class TestContracts : ITestInterface
    {
        ITestInterface Current { get; set; }

        private TestContracts()
        {
            Current = this;
        }

        #region ITestInterface Members

        bool ITestInterface.IsStarted
        {
            get; set;
        }

        void ITestInterface.Begin()
        {
            Contract.Requires(!Current.IsStarted);
            Contract.Ensures(Current.IsStarted);
        }

提前致谢！

Answer 1

好吧，为了不让Jon Skeet读得很好，这对我来说是正确的;）关于重写者如何接受合同并将它们放入实际班级的一点......

   [ContractClassFor(typeof(ITestInterface))] 
    class TestContracts : ITestInterface 
    { 

        private TestContracts() 
        { 
        } 

        #region ITestInterface Members 

        bool ITestInterface.IsStarted 
        { 
            get; set; 
        } 

        void ITestInterface.Begin() 
        { 
            ITestInterface iface = this;
            Contract.Requires(!iface.IsStarted); 
            Contract.Ensures(iface.IsStarted); 
        } 
    }

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