iequalitycomparer

Is this the best way to create a comparer for the equality of two dictionaries? This needs to be exact. Note that Entity.Columns is a dictionary of KeyValuePair(string, object) : public class EntityColumnCompare : IEqualityComparer<Entity> { public bool Equals(Entity a, Entity b) { var aCol = a.Columns.OrderBy(KeyValuePair => KeyValuePair.Key); var bCol = b.Columns.OrderBy(KeyValuePAir => KeyValuePAir.Key); if (aCol.SequenceEqual(bCol)) return true; else return false; } public int GetHashCode(Entity obj) { return obj.Columns.GetHashCode(); } } Also not too sure about the GetHashCode

I am writing this neat class implementing IEqualityComparer, so that I can just pass any anonymous type to it (or actually any type with properties) and it will automatically compare the types by comparing the property values of the types. public class CompareProperty<T> : IEqualityComparer<T> { private Type type; private PropertyInfo propInfo; private string _fieldName; public string fieldName { get; set; } public CompareProperty(string fieldName) { this.fieldName = fieldName; } public bool Equals<T>(T x, T y) { if (this.type == null) { type = x.GetType(); propInfo = type.GetProperty

I have an entity that I'd like to compare with a subset and determine to select all except the subset. So, my query looks like this: Products.Except(ProductsToRemove(), new ProductComparer()) The ProductsToRemove() method returns a List<Product> after it performs a few tasks. So in it's simplest form it's the above. The ProductComparer() class looks like this: public class ProductComparer : IEqualityComparer<Product> { public bool Equals(Product a, Product b) { if (ReferenceEquals(a, b)) return true; if (ReferenceEquals(a, null) || ReferenceEquals(b, null)) return false; return a.Id == b.Id; }

the 'Equal' and 'GetHashcode' method are exist in the object class, and our type inherit the object base class. what's the different between implement the two methods of the object directly and using the IComparer interface? if we overriding object's Equal and GetHashCode , and push to a hashtable , it will use the overring 's equal method? what' the differents of new a hashtable with the IEqualityComparer constructor? The IComparable interface is used when you need to be able to "sort" objects, and it gives you a method ( CompareTo ) that tells you if two objects are <, = or > . The

I was reading the source code of EqualityComparer<T>.Default and found that it's not so clever. Here is an example: enum MyEnum : int { A, B } EqualityComparer<MyEnum>.Default.Equals(MyEnum.A, MyEnum.B) //is as fast as EqualityComparer<int>.Default.Equals(0, 1) enum AnotherEnum : long { A = 1L, B = 2L } //is 8x slower than EqualityComparer<long>.Default.Equals(1L, 2L) The reason is obvious from the source code of the private method in EqualityComparer. private static EqualityComparer<T> CreateComparer() { //non-important codes are ignored if (c.IsEnum && (Enum.GetUnderlyingType(c) == typeof

Suppose I've got a generic MyClass<T> that needs to compare two objects of type <T> . Usually I'd do something like ... void DoSomething(T o1, T o2) { if(o1.Equals(o2)) { ... } } Now suppose my MyClass<T> has a constructor that supports passing a custom IEqualityComparer<T> , similar to Dictionary<T> . In that case I'd need to do ... private IEqualityComparer<T> _comparer; public MyClass() {} public MyClass(IEqualityComparer<T> comparer) { _comparer = comparer; } void DoSomething(T o1, T o2) { if((_comparer != null && _comparer.Equals(o1, o2)) || (o1.Equals(o2))) { ... } } To remove this