Unique Tags with HashSet in C# - Example You Can Run Online

Introduction

HashSet<T> expresses uniqueness directly and supports fast membership tests.

A case-insensitive comparer prevents differently cased spellings from becoming separate tags.

See how it works

Pick an operation to highlight its result in the diagram. Add a value that is already in the set to see that duplicates are ignored.

Runnable C# example

C#

Run code →

Program.cs

using System;
using System.Collections.Generic;
class Program
{
    static void Main()
    {
        var tags = new HashSet<string>(StringComparer.OrdinalIgnoreCase) { "C#", "dotnet", "c#" };
        Console.WriteLine(tags.Count);
    }
}

Result of running the code

Practice with the debugger

Set a breakpoint on an important assignment or condition, click Debug, and inspect the local values before stepping to the next line.

Practice with a challenge

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