C# - DictionaryEntry Example

DictionaryEntry. This C# type is used with Hashtable. The Hashtable collection provides a way to access objects based on a key. We use DictionaryEntry in a foreach-loop.

foreach

Type notes. Usually DictionaryEntry is part of a foreach-loop, but it can be used to store pairs together. This is similar to a KeyValuePair or Tuple.

KeyValuePair

Tuple

Foreach example. This example uses the Hashtable type and instantiates it upon the managed heap. Then 3 key-value pairs are added to the Hashtable instance.

Start We use the foreach-loop construct to loop over the contents of the Hashtable instance.

Hashtable

And The loop gives us a pair of values, encoded in a DictionaryEntry struct value.

struct

Also To access the key and value of a DictionaryEntry, please use the named properties.

using System;
using System.Collections;

// Create Hashtable with some keys and values.
Hashtable hashtable = new Hashtable();
hashtable.Add(1, "one");
hashtable.Add(2, "two");
hashtable.Add(3, "three");

// Enumerate the Hashtable.
foreach (DictionaryEntry entry in hashtable)
{
    Console.WriteLine("{0} = {1}", entry.Key, entry.Value);
}3 = three
2 = two
1 = one

Class example. DictionaryEntry is not tied to the Hashtable collection. You can create an instance to store a key-value pair anywhere.

And Because this type is a value type, it is copied onto the evaluation stack whenever used as a variable or parameter.

Info The DictionaryEntry struct stores 2 object references. Each object reference is 8 bytes on 64-bit systems.

using System;
using System.Collections;

class Program
{
    static DictionaryEntry GetData()
    {
        // Return DictionaryEntry as key-value pair.
        return new DictionaryEntry("cat", "frog");
    }

    static void Main()
    {
        var data = GetData();
        Console.WriteLine(data.Key);
        Console.WriteLine(data.Value);
    }
}cat
frog

A summary. To loop over a C# Hashtable collection, you can use the foreach-loop statement. Then access the properties on each DictionaryEntry.

Final note. The DictionaryEntry struct is not a class, and is stored on the stack when used as a local variable. It can be instantiated anywhere in C# programs.

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This page was last updated on Oct 11, 2023 (edit).

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