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Dictionary Class in C#
Dictionary in C# is a collection of keys and values. It is a generic collection class in the System.Collection.Generics namespace.
Syntax
Following is the syntax −
public class Dictionary<TKey,TValue>
Above, the key parameter is the type of keys in the dictionary, whereas TValue is the type of values.
Example
Let us now create a Dictionary and add some elements −
using System;
using System.Collections.Generic;
public class Demo {
public static void Main(){
Dictionary<string, string> dict = new Dictionary<string, string>();
dict.Add("One", "John");
dict.Add("Two", "Tom");
dict.Add("Three", "Jacob");
dict.Add("Four", "Kevin");
dict.Add("Five", "Nathan");
Console.WriteLine("Key/value pairs...");
foreach(KeyValuePair<string, string> res in dict){
Console.WriteLine("Key = {0}, Value = {1}", res.Key, res.Value);
}
}
}Output
This will produce the following output −
Key/value pairs... Key = One, Value = John Key = Two, Value = Tom Key = Three, Value = Jacob Key = Four, Value = Kevin Key = Five, Value = Nathan
Example
Now, let us see an example and remove some keys −
using System;
using System.Collections.Generic;
public class Demo {
public static void Main(){
Dictionary<string, string> dict = new Dictionary<string, string>();
dict.Add("One", "Kagido");
dict.Add("Two", "Ngidi");
dict.Add("Three", "Devillers");
dict.Add("Four", "Smith");
dict.Add("Five", "Warner");
Console.WriteLine("Count of elements = "+dict.Count);
Console.WriteLine("Removing some keys...");
dict.Remove("Four");
dict.Remove("Five");
Console.WriteLine("Count of elements (updated) = "+dict.Count);
Console.WriteLine("
Key/value pairs...");
foreach(KeyValuePair<string, string> res in dict){
Console.WriteLine("Key = {0}, Value = {1}", res.Key, res.Value);
}
Console.Write("
All the keys..
");
Dictionary<string, string>.KeyCollection allKeys = dict.Keys;
foreach(string str in allKeys){
Console.WriteLine("Key = {0}", str);
}
}
}Output
This will produce the following output −
Count of elements = 5 Removing some keys... Count of elements (updated) = 3 Key/value pairs... Key = One, Value = Kagido Key = Two, Value = Ngidi Key = Three, Value = Devillers All the keys.. Key = One Key = Two Key = Three
Updated on: 06-Nov-2019
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