Interface, which defines a generalized method that a value type or class implements to create a type-specific method for determining equality of instances.
Questions tagged [iequatable]
165 questions
229
votes
4 answers
What's the difference between IEquatable and just overriding Object.Equals()?
I want my Food class to be able to test whenever it is equal to another instance of Food. I will later use it against a List, and I want to use its List.Contains() method. Should I implement IEquatable or just override Object.Equals()? From…
devoured elysium
- 101,373
- 131
- 340
- 557
179
votes
5 answers
What is the difference between IEqualityComparer and IEquatable?
I want to understand the scenarios where IEqualityComparer and IEquatable should be used.
The MSDN documentation for both looks very similar.
Tilak
- 30,108
- 19
- 83
- 131
150
votes
11 answers
Distinct not working with LINQ to Objects
class Program
{
static void Main(string[] args)
{
List books = new List
{
new Book
{
Name="C# in Depth",
Authors = new List
{
…
Tanmoy
- 44,392
- 16
- 45
- 55
113
votes
5 answers
What's the difference between IComparable & IEquatable interfaces?
Both the interfaces seem to compare objects for equality, so what are the major differences between them?
SoftwareGeek
- 15,234
- 19
- 61
- 78
57
votes
4 answers
When To Use IEquatable And Why
What does IEquatable buy you, exactly? The only reason I can see it being useful is when creating a generic type and forcing users to implement and write a good equals method.
What am I missing?
Jack Kada
- 24,474
- 29
- 82
- 106
55
votes
5 answers
Is there a complete IEquatable implementation reference?
Many of my questions here on SO concerns IEquatable implementation. I found it being extremely difficult to implement correctly, because there are many hidden bugs in the naïve implementation, and the articles I found about it are quite incomplete.…
Jader Dias
- 88,211
- 155
- 421
- 625
53
votes
2 answers
Understanding IEquatable
When I implement objects that I want to compare using the IEquatable interface:
Why do I have to override Equals(object) method if I already implemented Equals(T)?
Can I use == and != operators once I implement IEquatable?
leora
- 188,729
- 360
- 878
- 1,366
38
votes
4 answers
Should IEquatable, IComparable be implemented on non-sealed classes?
Anyone have any opinions on whether or not IEquatable or IComparable should generally require that T is sealed (if it's a class)?
This question occurred to me since I'm writing a set of base classes intended to aid in the implementation of…
Phil
- 2,675
- 1
- 25
- 27
27
votes
3 answers
What should GetHashCode return when object's identifier is null?
Which of the following is correct/better, considering that identity property could be null.
public override int GetHashCode()
{
if (ID == null) {
return base.GetHashCode();
}
return ID.GetHashCode();
}
OR
public override int…
Dienekes
- 1,548
- 1
- 16
- 24
22
votes
2 answers
GetHashCode on null fields?
How do I deal with null fields in GetHashCode function?
Module Module1
Sub Main()
Dim c As New Contact
Dim hash = c.GetHashCode
End Sub
Public Class Contact : Implements IEquatable(Of Contact)
Public Name As String
Public…
Shimmy Weitzhandler
- 101,809
- 122
- 424
- 632
20
votes
5 answers
Can I overload an == operator on an Interface?
I have an interface like this:
public interface IFoo
{
int A {get;}
int B {get;}
}
and I have multiple classes implementing IFoo.
I want to check equality, not based on ReferenceEquality, but two IFoos should be considered equal, if both A and…
TDaver
- 7,164
- 5
- 47
- 94
20
votes
2 answers
Why does Equals(object) win over Equals(T) when using an inherited object in Hashset or other Collections?
I am aware of the fact that I always have to override Equals(object) and GetHashCode() when implementing IEquatable.Equals(T).
However, I don't understand, why in some situations the Equals(object) wins over the generic Equals(T).
For example why…
Marwie
- 3,177
- 3
- 28
- 49
19
votes
2 answers
Key comparisons for Linq GroupBy using Default EqualityComparer
I'm trying to do a Linq GroupBy on some objects using an explicit key type. I'm not passing an IEqualityComparer to the GroupBy, so according to the docs:
The default equality comparer Default is used to compare keys.
It explains the…
dan-gph
- 16,301
- 12
- 61
- 79
15
votes
4 answers
Should I use a concatenation of my string fields as a hash code?
I have an Address class in C# that looks like this:
public class Address
{
public string StreetAddress { get; set; }
public string RuralRoute { get; set; }
public string City { get; set; }
public string Province { get;…
cdmckay
- 31,832
- 25
- 83
- 114
10
votes
2 answers
How should I go about implementing Object.GetHashCode() for complex equality?
Basically, I have the following so far:
class Foo {
public override bool Equals(object obj)
{
Foo d = obj as Foo ;
if (d == null)
return false;
return this.Equals(d);
}
#region IEquatable…
Matthew Scharley
- 127,823
- 52
- 194
- 222