.NET dictionary with two keys and one value

.NET dictionary with two keys and one value

In .NET, you can implement a dictionary with two keys and one value by creating a custom class that represents a composite key and using it as the key in a standard dictionary.

Here's an example of how to do this:

public class TwoKey { public int Key1 { get; set; } public int Key2 { get; set; } public override bool Equals(object obj) { if (obj == null || GetType() != obj.GetType()) { return false; } TwoKey other = (TwoKey)obj; return Key1 == other.Key1 && Key2 == other.Key2; } public override int GetHashCode() { unchecked { int hash = 17; hash = hash * 23 + Key1.GetHashCode(); hash = hash * 23 + Key2.GetHashCode(); return hash; } } } Dictionary<TwoKey, string> dictionary = new Dictionary<TwoKey, string>(); // Adding values to the dictionary dictionary.Add(new TwoKey { Key1 = 1, Key2 = 2 }, "Value 1"); dictionary.Add(new TwoKey { Key1 = 3, Key2 = 4 }, "Value 2"); // Retrieving a value from the dictionary string value = dictionary[new TwoKey { Key1 = 1, Key2 = 2 }];

In this example, the TwoKey class represents a composite key with two integer values, Key1 and Key2. The Equals and GetHashCode methods are overridden to provide equality comparison and hashing based on both keys.

The TwoKey class is then used as the key type in a standard Dictionary with a string value type. Values can be added to the dictionary using instances of the TwoKey class as keys, and retrieved using the same.

Examples

  1. "How to create a .NET dictionary with two keys and one value?"

    Description: This query seeks information on creating a dictionary in .NET that can be indexed by two keys to retrieve a single value. This requirement often arises in scenarios where data needs to be efficiently organized and accessed using multiple identifiers.

    Code:

    using System; using System.Collections.Generic; class Program { static void Main(string[] args) { // Create a dictionary with Tuple<int, int> as the key type Dictionary<Tuple<int, int>, string> dualKeyDictionary = new Dictionary<Tuple<int, int>, string>(); // Add values to the dictionary dualKeyDictionary.Add(Tuple.Create(1, 2), "Value1"); dualKeyDictionary.Add(Tuple.Create(3, 4), "Value2"); // Retrieve values using dual keys Console.WriteLine(dualKeyDictionary[Tuple.Create(1, 2)]); // Output: Value1 Console.WriteLine(dualKeyDictionary[Tuple.Create(3, 4)]); // Output: Value2 } }

  2. "C# dictionary with composite key example"

    Description: This query is looking for examples or tutorials demonstrating how to implement a dictionary in C# with a composite key, where the key consists of multiple values.

    Code:

    using System; using System.Collections.Generic; class Program { static void Main(string[] args) { // Define a class for the composite key public class CompositeKey { public int FirstKey { get; set; } public int SecondKey { get; set; } // Implement equality members for use as a dictionary key public override bool Equals(object obj) { if (obj == null || GetType() != obj.GetType()) return false; var other = (CompositeKey)obj; return FirstKey == other.FirstKey && SecondKey == other.SecondKey; } public override int GetHashCode() { return FirstKey.GetHashCode() ^ SecondKey.GetHashCode(); } } // Create a dictionary with CompositeKey as the key type Dictionary<CompositeKey, string> compositeKeyDictionary = new Dictionary<CompositeKey, string>(); // Add values to the dictionary compositeKeyDictionary.Add(new CompositeKey { FirstKey = 1, SecondKey = 2 }, "Value1"); compositeKeyDictionary.Add(new CompositeKey { FirstKey = 3, SecondKey = 4 }, "Value2"); // Retrieve values using composite keys Console.WriteLine(compositeKeyDictionary[new CompositeKey { FirstKey = 1, SecondKey = 2 }]); // Output: Value1 Console.WriteLine(compositeKeyDictionary[new CompositeKey { FirstKey = 3, SecondKey = 4 }]); // Output: Value2 } }

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