How to compare Enum values in C#?

Enum.CompareTo(Object) Method is used to compare the current instance to a specified object and returns an indication of their relative values.

Syntax:

public int CompareTo (object target);

Here, the target is an object to compare or it may be null.

Returns: This method returns a signed number which shows the relative values of the current instance and target as follows:

• Less than zero: If the value of the current instance is less than the value of target.
• Zero: If the value of the current instance is equal to the value of the target.
• Greater than zero: If the value of the current instance is greater than the value of the target or the target is null.

Exceptions:

• ArgumentException: If the target and current instance are not the same types.
• InvalidOperationException: If the instance is not type SByte, Int16, Int32, Int64, Byte, UInt16, UInt32, or UInt64.
• NullReferenceException: If the current instance is null.

Below programs illustrate the use of the above-discussed method:

Example 1:

// C# program to demonstrate the
// Enum.CompareTo(Object) Method
using System;

public class GFG
{

    enum Color
    {
        RED, GREEN, BLUE
    };

    // Driver method
    public static void Main(String[] args)
    {
        Color c1 = Color.RED;
        Color c2 = Color.GREEN;
        Color c3 = Color.RED;
        Color c4 = Color.BLUE;

        Console.Write("Comparing {0} with {1} : ", c1, c2);

        // CompareTo method
        Console.WriteLine(c1.CompareTo(c2));

        Console.Write("Comparing {0} with {1} : ", c1, c3);

        // CompareTo method
        Console.WriteLine(c1.CompareTo(c3));

        Console.Write("Comparing {0} with {1} : ", c4, c2);

        // CompareTo method
        Console.WriteLine(c4.CompareTo(c2));

    }
}

Output:

Comparing RED with GREEN : -1
Comparing RED with RED : 0
Comparing BLUE with GREEN : 1

Example 2:

// C# program to demonstrate the
// Enum.CompareTo(Object) Method
using System;

public class GFG
{

    enum Color{Red, Blue};

    enum Seasons {Winter, Summer};

    // Driver method
    public static void Main(String[] args)
    {
        Color c1 = Color.Red;
        Color c2 = Color.Blue;

        Seasons s1 = Seasons.Winter;
        Seasons s2 = Seasons.Summer;

        Console.Write("Comparing {0} with {1} : ", c1, c2);

        // CompareTo method
        Console.WriteLine(c1.CompareTo(c2));

        Console.Write("Comparing {0} with {1} : ", c1, s1);

        // using CompareTo method
        // it will give exception
        // as target and the current
        // instance are not the same
        // types
        Console.WriteLine(c1.CompareTo(s1));


    }
}

Runtime Error:

Unhandled Exception:
System.ArgumentException: Object must be the same type as the enum. The type passed in was ‘GFG+Seasons’; the enum type was ‘GFG+Color’.
at System.Enum.CompareTo (System.Object target) in :0

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.enum.compareto?view=netframework-4.8