How to convert a dictionary to a list in C#

Converting a dictionary to a list is a common task, and C# provides a few simple ways to achieve this using LINQ or loops.

1. Convert a Dictionary to a List of KeyValuePair

The simplest way to convert a dictionary to a list is by using the LINQ ToList() method. This method will convert each key-value pair into a KeyValuePair<TKey, TValue> in a list.

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

var dictionary = new Dictionary<int, string>()
{
    [100] = "Bob",
    [101] = "Tom",
    [102] = "Teddy"
};

var list = dictionary.ToList();

foreach(var kvp in list)
{
    Console.WriteLine($"{kvp.Key}={kvp.Value}");
}

Output:

100=Bob
101=Tom
102=Teddy

When used on a dictionary, the ToList() method returns a list of KeyValuePair objects, where each KeyValuePair contains a key and its corresponding value from the dictionary.

2. Convert Dictionary Keys to a List

If you only need the keys from the dictionary, you can use ToList() on the Dictionary.Keys collection.

var list = dictionary.Keys.ToList();
foreach(var key in list)
{
    Console.WriteLine(key);
}

Output:

100
101
102

3. Convert Dictionary Values to a List

If you are only interested in the values of the dictionary, you can use ToList() on the Dictionary.Values collection.

var list = dictionary.Values.ToList();
foreach(var val in list)
{
    Console.WriteLine(val);
}

Output:

Bob
Tom
Teddy

4. Convert Dictionary to a List of Tuples

To convert a dictionary to a list of tuples, you can use LINQ's Select() method to project each key-value pair as a tuple. The result can then be converted to a list using ToList().

var list = dictionary.Select(kvp => (Id: kvp.Key, Name: kvp.Value)).ToList();

foreach(var tuple in list)
{
    Console.WriteLine($"{tuple.Name} has id {tuple.Id}");
}

Output:

Bob has id 100
Tom has id 101
Teddy has id 102

5. Using a Loop to Convert Dictionary to a List

Sometimes you might want more control over how the dictionary is converted to a list. You can manually loop through the dictionary and add items to a list as needed.

var list = new List<KeyValuePair<int, string>>();

foreach(var kvp in dictionary)
{
    if (kvp.Key > 100)
    {
        list.Add(kvp);
    }
}
Console.WriteLine($"List has {list.Count} items");

Output:

List has 2 items