DictionaryTKey TValue
suggest changeDictionary<TKey, TValue> is a map. For a given key there can be one value in the dictionary.
using System.Collections.Generic;
var people = new Dictionary<string, int>
{
{ "John", 30 }, {"Mary", 35}, {"Jack", 40}
};
// Reading data
Console.WriteLine(people["John"]); // 30
Console.WriteLine(people["George"]); // throws KeyNotFoundException
int age;
if (people.TryGetValue("Mary", out age))
{
Console.WriteLine(age); // 35
}
// Adding and changing data
people["John"] = 40; // Overwriting values this way is ok
people.Add("John", 40); // Throws ArgumentException since "John" already exists
// Iterating through contents
foreach(KeyValuePair<string, int> person in people)
{
Console.WriteLine("Name={0}, Age={1}", person.Key, person.Value);
}
foreach(string name in people.Keys)
{
Console.WriteLine("Name={0}", name);
}
foreach(int age in people.Values)
{
Console.WriteLine("Age={0}", age);
}
Duplicate key when using collection initialization
var people = new Dictionary<string, int>
{
{ "John", 30 }, {"Mary", 35}, {"Jack", 40}, {"Jack", 40}
}; // throws ArgumentException since "Jack" already exists
Found a mistake? Have a question or improvement idea?
Let me know.
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