c# - 对具有不同参数的相同方法调用的最小起订量期望

Question

我正在尝试在一个循环中设置一个模拟对象，该循环将为具有不同参数的函数调用返回不同的值:

var myMock= new Mock<IInterface>();
for (int i = 0; i < fromKeys.Count; ++i)
{
    var value= new[] {new[] {1.0 + i}};
    _values.Add(value);
    myMock.Setup(x => x.Provide(fromKeys[i])).Returns(new Sth(fromKeys[i], value));
}
_myObject = myMock.Object;

但是当我用生产代码中的第一个键调用 Provide 时它崩溃了(而不是在测试设置期间):

System.Reflection.TargetInvocationException : Exception has been thrown by the target of an invocation.
  ----> System.ArgumentOutOfRangeException : Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
   at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, ref SignatureStruct sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
   at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Delegate.DynamicInvokeImpl(Object[] args)
   at Moq.Evaluator.SubtreeEvaluator.Evaluate(Expression e)
   at Moq.Matchers.LazyEvalMatcher.Matches(Object value)
   at Moq.MethodCall.Matches(ICallContext call)
   at System.Linq.Enumerable.LastOrDefault(IEnumerable`1 source, Func`2 predicate)
   at Moq.ExtractProxyCall.HandleIntercept(ICallContext invocation, InterceptStrategyContext ctx)
   at Moq.Interceptor.Intercept(ICallContext invocation)
   at Castle.DynamicProxy.AbstractInvocation.Proceed()
   at Castle.Proxies.IBrownianProviderProxy.Provide(BrowniansKey keys)
   at MyCode.....

如何设置？

Answer 1

这是一个闭包问题。 x => x.Provide(fromKeys[i]) 直到稍后才被评估。等到后面求值的时候，i == fromKeys.Count，已经越界了。如果这没有意义，我建议阅读更多关于闭包的内容。不过，简单的解决方案是添加一行，使您的代码看起来像这样(在 for 循环中)

for (int i = 0; i < fromKeys.Count; ++i)
{
    int j = i;
    myMock.Setup(x => x.Provide(fromKeys[j])).Returns(new Sth(fromKeys[j], _values[j]));
}