I'm having in issue where a certain piece of code is running as expected in .NET 4.0 but not in Mono 2.6 (in Unity3D). Please have a look:
void Test()
{
Func<string, MemberInfo> get = name => typeof(HSTest).GetField(name, BindingFlags.Public | BindingFlags.Instance);
var m1 = new TestMember { MemberInfo = get("x") };
var m2 = new TestMember { MemberInfo = get("y") };
var m3 = new TestMember { MemberInfo = get("x") };
var m4 = new TestMember { MemberInfo = get("x") };
var m5 = new TestMember { MemberInfo = get("a") };
var m6 = new TestMember { MemberInfo = get("b") };
var l1 = new List<TestMember> { m1, m2, m3 };
var l2 = new List<TestMember> { m4, m5, m6 };
var ll = new List<List<TestMember>> { l1, l2 };
var comparer = new TestMemberComparer();
var res = IntersectAll(ll, comparer);
res.Foreach(Debug.Log); // In .NET this prints "x" in Mono it doesn't print anything
}
// Credits to Jon Skeet
public static List<T> IntersectAll<T>(List<List<T>> lists, IEqualityComparer<T> comparer)
{
HashSet<T> hashSet = null;
foreach (var list in lists)
{
if (hashSet == null)
{
hashSet = new HashSet<T>(list, comparer);
}
else
{
hashSet.IntersectWith(list);
}
}
return hashSet == null ? new List<T>() : hashSet.ToList();
}
}
public class TestMember
{
public MemberInfo MemberInfo { get; set; }
}
public class TestMemberComparer : IEqualityComparer<TestMember>
{
public bool Equals(TestMember x, TestMember y)
{
return x.MemberInfo.Equals(y.MemberInfo);
}
public int GetHashCode(TestMember obj)
{
return obj.MemberInfo.GetHashCode();
}
}
public class HSTest
{
public int x;
public int y;
public int z;
public int a;
public int b;
public int c;
}
In .NET I'm getting 'x' as the result of the intersection, in Mono I'm not getting anything back.
Any ideas?
EDIT:
Using the name instead of the actual MemberInfo object doesn't help either
public class TestMemberComparer : IEqualityComparer<TestMember>
{
public bool Equals(TestMember x, TestMember y)
{
return x.MemberInfo.Name.Equals(y.MemberInfo.Name);
}
public int GetHashCode(TestMember obj)
{
return obj.MemberInfo.Name.GetHashCode();
}
}
I should also mention that using a different way to intersect doesn't cause any issues (Both when using MemberInfo
and MemberInfo.Name
in the GetHashCode
and Equals
):
var res = ll.Aggregate((p, n) => p.Intersect(n, comparer).ToList());
EDIT: Here's a test with some logs inside the comparer
void Test()
{
// ... define everything like in previous code
var comparer = new TestMemberComparer();
var hs = new HashSet<TestMember>(l1, comparer);
hs.IntersectWith(l2);
hs.ToList().Foreach(Debug.Log);
}
public class TestMemberComparer : IEqualityComparer<TestMember>
{
public bool Equals(TestMember left, TestMember right)
{
bool result = left.MemberInfo.Name.Equals(right.MemberInfo.Name);
Debug.Log("Comparing `" + left.MemberInfo.Name + "` with `" + right.MemberInfo.Name + "` Result: " + result);
return result;
}
public int GetHashCode(TestMember obj)
{
int hc = obj.MemberInfo.Name.GetHashCode();
Debug.Log("Hash code: " + hc);
return hc;
}
}
All I got when executing is:
Hash code: 120
Hash code: 120
Hash code: 121
Comparing `x` with `x` Result: True
Hash code: 120
Hash code: 120
Hash code: 120
Comparing `x` with `x` Result: True
Hash code: 121
Comparing `y` with `y` Result: True
Hash code: 97
Hash code: 97
Hash code: 98
Hash code: 98
I suspect that it's just a matter of MemberInfo.Equals
not working as you expect. That's easy to test:
var m1 = get("x");
var m2 = get("x");
Console.WriteLine(m1.Equals(m2));
If that prints False, then that's the issue, and you should add your own caching.
See more on this question at Stackoverflow