Hashma - cywongg/2025 GitHub Wiki

For a quick and clean solution in C# that is both efficient and readable, you can use LINQ with built-in dictionary methods like TryGetValue and FirstOrDefault. Here's how you can do it:

Efficient and Clean LINQ-Based Approach

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        // Example dictionary where keys are strings and values are lists of objects
        var hashMap = new Dictionary<string, List<object>>
        {
            { "key1", new List<object> { "value1", "value2" } },
            { "key2", new List<object> { "value3", "value4" } },
            { "key3", new List<object> { "value5", "value6" } }
        };

        // List of keys to search for
        var keysToFind = new List<string> { "key1", "key3" };

        // Use LINQ to get the first values for matching keys
        var firstValues = keysToFind
            .Select(key => hashMap.TryGetValue(key, out var values) ? values.FirstOrDefault() : null)
            .Where(value => value != null)
            .ToList();

        // Output the results
        Console.WriteLine("First values of matching keys:");
        foreach (var value in firstValues)
        {
            Console.WriteLine(value);
        }
    }
}

Key Points:

TryGetValue: Efficiently retrieves the values for a key without throwing exceptions if the key doesn't exist.
FirstOrDefault: Retrieves the first value from the list or null if the list is empty.
Where(value => value != null): Filters out any null results, ensuring only valid values are returned.
LINQ: Makes the code succinct and easier to read by chaining operations.

Why This Is Efficient:

Minimized Loops: Instead of manually iterating and checking keys, LINQ handles this in a single pipeline.
Efficient Access: TryGetValue avoids the overhead of using ContainsKey followed by an indexer lookup.
Short-Circuiting: Operations like FirstOrDefault stop as soon as the first value is found, making it faster for large lists.

Sample Output:

For the dictionary:

{
    "key1": ["value1", "value2"],
    "key2": ["value3", "value4"],
    "key3": ["value5", "value6"]
}

And the list of keys:

["key1", "key3"]

The output will be:

First values of matching keys:
value1
value5

Summary:

This LINQ-based approach is clean, concise, and avoids excessive boilerplate code, making it both efficient and easy to maintain.