iequalitycomparer

I happened to have seen some code where this guy passed a lambda expression to a ArrayList.Sort(IComparer here) or a IEnumerable.SequenceEqual(IEnumerable list, IEqualityComparer here) where an IComparer or an IEqualityComparer was expected. I can't be sure if I saw it though, or I am just dreaming. And I can't seem to find an extension on any of these collections that accepts a Func<> or a delegate in their method signatures. Is there such an overload/extension method? Or, if not, is it possible to muck around like this and pass an algorithm (read delegate) where a single-method interface is

I am trying to implement an IEqualityComparer that has a tolerance on a date comparison. I have also looked into this question . The problem is that I can't use a workaround because I am using the IEqualityComparer in a LINQ .GroupJoin() . I have tried a few implementations that allow for tolerance. I can get the Equals() to work because I have both objects but I can't figure out how to implement GetHashCode() . My best attempt looks something like this: public class ThingWithDateComparer : IEqualityComparer<IThingWithDate> { private readonly int _daysToAdd; public ThingWithDateComparer(int

If I have an object of type MyBull and a List<MyBull> orig : // Just an example MyBull x = getMeTheObjectWithIdFromDB(9); orig.add(x); // Again same? data object MyBull y = getMeTheObjectWithIdFromDB(9); Why is this false then? // This is false, even though all the properties // of x and y are the same. orig.Contains<MyBull>(y); By default objects will expose reference based equality. If you want custom rules, such as equality based on id fields, you need to override the Equals and GetHashCode methods. If you can use LINQ then you can class Vessel { public int id { get; set; } public string

I have this var n = ItemList.Select(s => new { s.Vchr, s.Id, s.Ctr, s.Vendor, s.Description, s.Invoice }).ToList(); n.AddRange(OtherList.Select(s => new { s.Vchr, s.Id, s.Ctr, s.Vendor, s.Description, s.Invoice }).ToList();); I would like to do this if it where allowed n = n.Distinct((x, y) => x.Vchr == y.Vchr)).ToList(); I tried using the generic LambdaComparer but since im using anonymous types there is no type associate it with. "Help me Obi Wan Kenobi, you're my only hope" JaredPar The trick is to create a comparer that only works on inferred types. For instance: public class Comparer<T> :

I want to understand the scenarios where IEqualityComparer<T> and IEquatable<T> should be used. The MSDN documentation for both looks very similar. IEqualityComparer<T> is an interface for an object that performs the comparison on two objects of the type T . IEquatable<T> is for an object of type T so that it can compare itself to another. When deciding whether to use IEquatable<T> or IEqualityComparer<T> , one could ask: Is there a preferred way of testing two instances of T for equality, or are there several equally valid ways? If there is only one way of testing two instances of T for

Again this sample is a very simplified version of my actual problem involving a custom comparer for linq grouping. What have I done wrong? The code below produces the result below (1.2, 0), (4.1, 0), (4.1, 0), (1.1, 0), however I was expecting the following since 1.1 and 1.2 are < 1.0 apart. (1.2, 0), (1.1, 0), (4.1, 0), (4.1, 0), class Program { static void Main(string[] args) { IEnumerable<Point> points = new List<Point> { new Point(1.1, 0.0) , new Point(4.1, 0.0) , new Point(1.2, 0.0) , new Point(4.1, 0.0) }; foreach (var group in points.GroupBy(p => p, new PointComparer())) { foreach (var