Check if a HashSet is a proper superset of the specified collection in C#

The IsProperSupersetOf() method in C# checks if a HashSet is a proper superset of the specified collection. A proper superset means the HashSet contains all elements of the other collection plus at least one additional element.

Syntax

Following is the syntax for using the IsProperSupersetOf() method −

public bool IsProperSupersetOf(IEnumerable<T> other)

Parameters

• other − The collection to compare with the current HashSet.

Return Value

Returns true if the HashSet is a proper superset of the specified collection; otherwise, false.

Using IsProperSupersetOf() with Integer HashSet

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      HashSet<int> set1 = new HashSet<int>();
      set1.Add(30);
      set1.Add(60);
      set1.Add(70);
      set1.Add(80);
      set1.Add(100);
      set1.Add(125);
      set1.Add(150);
      set1.Add(200);
      Console.WriteLine("Elements in HashSet1");
      foreach(int val in set1) {
         Console.WriteLine(val);
      }
      HashSet<int> set2 = new HashSet<int>();
      set2.Add(30);
      set2.Add(60);
      set2.Add(70);
      Console.WriteLine("Elements in HashSet2");
      foreach(int val in set2) {
         Console.WriteLine(val);
      }
      Console.WriteLine("Is set1 a proper superset of set2? " + set1.IsProperSupersetOf(set2));
   }
}

The output of the above code is −

Elements in HashSet1
30
60
70
80
100
125
150
200
Elements in HashSet2
30
60
70
Is set1 a proper superset of set2? True

Using IsProperSupersetOf() with String HashSet

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      HashSet<string> set1 = new HashSet<string>();
      set1.Add("AB");
      set1.Add("CD");
      set1.Add("EF");
      set1.Add("GH");
      set1.Add("IJ");
      set1.Add("KL");
      set1.Add("MN");
      set1.Add("OP");
      Console.WriteLine("Elements in HashSet1");
      foreach(string val in set1) {
         Console.WriteLine(val);
      }
      HashSet<string> set2 = new HashSet<string>();
      set2.Add("EF");
      set2.Add("KL");
      Console.WriteLine("Elements in HashSet2");
      foreach(string val in set2) {
         Console.WriteLine(val);
      }
      Console.WriteLine("Is set1 a proper superset of set2? " + set1.IsProperSupersetOf(set2));
   }
}

The output of the above code is −

Elements in HashSet1
AB
CD
EF
GH
IJ
KL
MN
OP
Elements in HashSet2
EF
KL
Is set1 a proper superset of set2? True

Edge Cases with IsProperSupersetOf()

Example

using System;
using System.Collections.Generic;

public class Demo {
   public static void Main() {
      HashSet<int> set1 = new HashSet<int> {1, 2, 3};
      HashSet<int> set2 = new HashSet<int> {1, 2, 3};
      HashSet<int> set3 = new HashSet<int> {1, 2, 3, 4};
      HashSet<int> emptySet = new HashSet<int>();
      
      Console.WriteLine("set1: {1, 2, 3}");
      Console.WriteLine("set2: {1, 2, 3}");
      Console.WriteLine("set3: {1, 2, 3, 4}");
      Console.WriteLine("emptySet: {}");
      Console.WriteLine();
      
      Console.WriteLine("set1.IsProperSupersetOf(set2): " + set1.IsProperSupersetOf(set2));
      Console.WriteLine("set3.IsProperSupersetOf(set1): " + set3.IsProperSupersetOf(set1));
      Console.WriteLine("set1.IsProperSupersetOf(emptySet): " + set1.IsProperSupersetOf(emptySet));
   }
}

The output of the above code is −

set1: {1, 2, 3}
set2: {1, 2, 3}
set3: {1, 2, 3, 4}
emptySet: {}

set1.IsProperSupersetOf(set2): False
set3.IsProperSupersetOf(set1): True
set1.IsProperSupersetOf(emptySet): True

Key Rules

• Returns false if both collections have the same elements (not a proper superset).

• Returns true if the HashSet contains all elements of the other collection plus at least one additional element.

• Any non-empty HashSet is a proper superset of an empty collection.

Conclusion

The IsProperSupersetOf() method determines if a HashSet contains all elements of another collection plus additional elements. It returns false for identical sets and true when the HashSet has extra elements beyond those in the compared collection.