What are the ways to check equality in C#

Chethan Jk

4y844C#

2 Replies

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Rajanikant Hawaldar4y ago
Accepted answer
The ReferenceEquals() method - checks if two reference type variables(classes, not structs) are referred to the same memory address.

The virtual Equals() method. (System.Object) - checks if two objects are equivalent.

The static Equals() method - is used to handle problems when there is a null value in the check.

The Equals method from IEquatable interface.

The comparison operator == - usually means the same as ReferenceEquals, it checks if two variables point to the same memory address. The gotcha is that this operator can be override to perform other types of checks. In strings, for instance, it checks if two different instances are equivalent.
Sachin Singh4y ago
'==" (for value types like int, double etc ) and Equals() method (for Complex type/Reference types)
are the two approach.
But if you are talking about reference type like classes then for reference type, as equals() method only compares the reference so you will always get false.
To overcome this you can override the equals() and GetHasCode method.
public class Employee
{
public int Id{get;set;}
public string Name {get;set;}

public override bool Equals(object obj)
    {
        var emp= obj as Employee;
        if(emp== null) return false;
        return Id== emp.Id && Name== emp.Name;
    }
}

public override int GetHashCode()
    {
        return Name.GetHasCode()*Id;
    }

Employee  emp1= new Employee()
{
Name="Sachin", Id=1
}

Employee  emp2= new Employee()
{
Name="Sachin", Id=1
}

bool isEqual=emp1.Equals(emp2); // true