//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 DifferentNonNullReferencesReturnNull()
{
// Just to be extra careful, make two different references to equal strings.
// That way we know we're not actually doing comparisons!
string x1 = new string(new [] { 'x' });
string x2 = new string(new [] { 'x' });
Assert.AreNotSame(x1, x2);
Assert.IsNull(PartialComparer.ReferenceCompare(x1, x2));
}
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 DefaultEqualReturnsNull()
{
Assert.IsNull(PartialComparer.Compare(4, 4));
}
public void DefaultGreaterThanReturnsGreaterThanZero()
{
Assert.IsTrue(PartialComparer.Compare(5, 3) > 0);
}
public void DefaultLessThanReturnsLessThanZero()
{
Assert.IsTrue(PartialComparer.Compare(3, 5) < 0);
}
public void NonNullGreaterThanNull()
{
Assert.AreEqual(1, PartialComparer.ReferenceCompare("x", null).Value);
}
public void TwoNullReferencesReturnZero()
{
Assert.AreEqual(0, PartialComparer.ReferenceCompare <string>(null, null).Value);
}
public void NullLessThanNonNull()
{
Assert.AreEqual(-1, PartialComparer.ReferenceCompare(null, "x").Value);
}
public void DifferentNonNullReferencesReturnMaybe()
{
Assert.IsNull(PartialComparer.Equals("first", "second"));
}
public void NonNullAndNullAreUnequal()
{
Assert.IsFalse(PartialComparer.Equals("non-null", null).Value);
}
public void EqualNonNullReferencesReturnZero()
{
Assert.AreEqual(0, PartialComparer.ReferenceCompare("x", "x").Value);
}
public void NullAndNonNullAreUnequal()
{
Assert.IsFalse(PartialComparer.Equals <string>(null, "non-null").Value);
}
public void TwoNullReferencesAreEqual()
{
Assert.IsTrue(PartialComparer.Equals <string>(null, null).Value);
}