Double.Equals() Method in C# with Examples

The Double.Equals() method in C# is used to determine whether two instances of Double represent the same value. This method provides a reliable way to compare double values and handles special cases like NaN (Not a Number) values correctly.

Syntax

The Double.Equals() method has two overloads −

public bool Equals(double obj);
public override bool Equals(object obj);

Parameters

• obj (first overload) − A Double value to compare to the current instance.

• obj (second overload) − An object to compare with the current instance.

Return Value

Returns true if the specified value is equal to the current instance; otherwise, false. For the object overload, it returns true only if the object is a Double and represents the same value.

Using Double.Equals() with Double Values

Example

using System;

public class Demo {
    public static void Main() {
        double d1 = 150.0;
        double d2 = 150.0;
        double d3 = 150.1;
        
        Console.WriteLine("Double1 Value = " + d1);
        Console.WriteLine("Double2 Value = " + d2);
        Console.WriteLine("Double3 Value = " + d3);
        Console.WriteLine("d1.Equals(d2) = " + d1.Equals(d2));
        Console.WriteLine("d1.Equals(d3) = " + d1.Equals(d3));
    }
}

The output of the above code is −

Double1 Value = 150
Double2 Value = 150
Double3 Value = 150.1
d1.Equals(d2) = True
d1.Equals(d3) = False

Using Double.Equals() with Object Parameter

Example

using System;

public class Demo {
    public static void Main() {
        double d1 = 150.0;
        object obj1 = 150.0;  // Boxing a double
        object obj2 = 150;    // Boxing an int
        object obj3 = "150";  // String object
        
        Console.WriteLine("Double Value = " + d1);
        Console.WriteLine("Object1 (double) = " + obj1);
        Console.WriteLine("Object2 (int) = " + obj2);
        Console.WriteLine("Object3 (string) = " + obj3);
        
        Console.WriteLine("d1.Equals(obj1) = " + d1.Equals(obj1));
        Console.WriteLine("d1.Equals(obj2) = " + d1.Equals(obj2));
        Console.WriteLine("d1.Equals(obj3) = " + d1.Equals(obj3));
    }
}

The output of the above code is −

Double Value = 150
Object1 (double) = 150
Object2 (int) = 150
Object3 (string) = 150
d1.Equals(obj1) = True
d1.Equals(obj2) = False
d1.Equals(obj3) = False

Handling Special Values

The Double.Equals() method correctly handles special double values like NaN, PositiveInfinity, and NegativeInfinity −

Example

using System;

public class Demo {
    public static void Main() {
        double nan1 = Double.NaN;
        double nan2 = Double.NaN;
        double posInf = Double.PositiveInfinity;
        double negInf = Double.NegativeInfinity;
        
        Console.WriteLine("NaN equals NaN: " + nan1.Equals(nan2));
        Console.WriteLine("PositiveInfinity equals PositiveInfinity: " + 
                         Double.PositiveInfinity.Equals(posInf));
        Console.WriteLine("PositiveInfinity equals NegativeInfinity: " + 
                         posInf.Equals(negInf));
    }
}

The output of the above code is −

NaN equals NaN: True
PositiveInfinity equals PositiveInfinity: True
PositiveInfinity equals NegativeInfinity: False

Double.Equals() vs == Operator

Conclusion

The Double.Equals() method provides a robust way to compare double values, especially when dealing with special values like NaN. It offers type-safe comparison and handles object comparisons by checking the type before comparing values, making it more reliable than the equality operator in certain scenarios.