//合并操作符用于多级比较
public int Compare(Product first, Product second)
{
return(PartialComparer.Compare(first, second) ??
PartialComparer.Compare(first.Price, second.Price) ??
PartialComparer.Compare(first.SupplierID, second.SupplierID) ??
PartialComparer.Compare(first.Name, second.Name) ?? 0);
}
public void CompareReturnsNullWhenSpecifiedComparerReturnsZero()
{
MockRepository factory = new MockRepository();
IComparer <string> comparer = factory.CreateMock <IComparer <string> >();
Expect.Call(comparer.Compare("first", "second")).Return(0);
factory.ReplayAll();
Assert.IsNull(PartialComparer.Compare(comparer, "first", "second"));
factory.VerifyAll();
}
public void DefaultGreaterThanReturnsGreaterThanZero()
{
Assert.IsTrue(PartialComparer.Compare(5, 3) > 0);
}
public void DefaultEqualReturnsNull()
{
Assert.IsNull(PartialComparer.Compare(4, 4));
}
public void DefaultLessThanReturnsLessThanZero()
{
Assert.IsTrue(PartialComparer.Compare(3, 5) < 0);
}