C# Dictionary Example

The Dictionary is related to System.Collections.Generic namespace. Dictionary contains on key-value pairs. Where each key is associated with a unique value. Dictionary can store specific type value for example if you are making a dictionary of int type then it can only store integer type values. On other hand hashtable can store any data type value.

Features with dictionary in C#:

• Creating a Dictionary:

  You need to import the System.Collections.Generic namespace to work with a Dictionary. To create a Dictionary, you can use the following code:

  Example

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  using System;

  using System.Collections.Generic;

  Dictionary<string,int> dictfruitprices = new Dictionary<string,int>();

  Dictionary<string,string> dictfruitnames = new Dictionary<string,string>();

  using System;

  using System.Collections.Generic;

  Dictionary<string,int> dictfruitprices = new Dictionary<string,int>();

  Dictionary<string,string> dictfruitnames = new Dictionary<string,string>();

• Adding Key-Value Pairs:

  You can add key-value pairs to a Dictionary using the Add method or by using the indexer:

  Example

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  // inserting fruit items in key-value pair

  dictfruitprices.Add("Apple",16);

  dictfruitprices.Add("Orange",12);

  dictfruitprices.Add("Cherry",18);

  dictfruitprices["Papaya"] = 20;

  dictfruitprices["Grape"] = 6;

  // inserting fruit items in key-value pair

  dictfruitnames.Add("Apple","Red");

  dictfruitnames.Add("Mango","Yellow");

  dictfruitnames.Add("Cherry","Red");

  dictfruitnames.Add("Orange","Dark Orange");

  dictfruitnames["Grape"] = "Violet";

  dictfruitnames.["Kiwi"] = "Spring Green";

  // inserting fruit items in key-value pair

  dictfruitprices.Add("Apple",16);

  dictfruitprices.Add("Orange",12);

  dictfruitprices.Add("Cherry",18);

  dictfruitprices["Papaya"] = 20;

  dictfruitprices["Grape"] = 6;

  // inserting fruit items in key-value pair

  dictfruitnames.Add("Apple","Red");

  dictfruitnames.Add("Mango","Yellow");

  dictfruitnames.Add("Cherry","Red");

  dictfruitnames.Add("Orange","Dark Orange");

  dictfruitnames["Grape"] = "Violet";

  dictfruitnames.["Kiwi"] = "Spring Green";

• Accessing Values:

  You can retrieve values from the Dictionary using their associated keys:

  Example

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  // Returns 20

  int fruitprice = dictfruitprices["Papaya"];

  // Returns Violet

  int fruitcolor = dictfruitnames["Grape"];

  // Returns 20

  int fruitprice = dictfruitprices["Papaya"];

  // Returns Violet

  int fruitcolor = dictfruitnames["Grape"];

• Checking for Key Existence:

  You can check if a key exists in the Dictionary using the ContainsKey method:

  Example

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  // Returns true

  bool containsAlice = dictfruitprices.ContainsKey("Papaya");

  // Returns true

  bool containsAlice = dictfruitnames.ContainsKey("Grape");

  // Returns true

  bool containsAlice = dictfruitprices.ContainsKey("Papaya");

  // Returns true

  bool containsAlice = dictfruitnames.ContainsKey("Grape");

• Iterating through a Dictionary:

  You can use a foreach loop or LINQ to iterate through the key-value pairs in a Dictionary:

  Example

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  foreach (var item1 in dictfruitprices)

  {

  Console.WriteLine($"{item1.Key}: {item1.Value}");

  }

  foreach (var item2 in dictfruitnames)

  {

  Console.WriteLine($"{item2.Key}: {item2.Value}");

  }

  foreach (var item1 in dictfruitprices)

  {

  Console.WriteLine($"{item1.Key}: {item1.Value}");

  }

  foreach (var item2 in dictfruitnames)

  {

  Console.WriteLine($"{item2.Key}: {item2.Value}");

  }

• Removing Key-Value Pairs:

  You can remove key-value pairs from the Dictionary using the Remove method:

  Example

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  dictfruitprices.Remove("Orange");

  dictfruitnames.Remove("Orange");

  dictfruitprices.Remove("Orange");

  dictfruitnames.Remove("Orange");

• Count of Key-Value Pairs:

  You can find the number of key-value pairs in the Dictionary using the Count property:

  Example

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  int count1 = dictfruitprices.Count;

  int count2 = dictfruitnames.Count;

  int count1 = dictfruitprices.Count;

  int count2 = dictfruitnames.Count;

• Dictionary in C# with Example

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  using System;

  using System.Collections.Generic;

  public class CSharpProgram

  {

  public static void Main(string[] arge)

  {

  Dictionary<string,int> dictfruitprices = new Dictionary<string,int>();

  Dictionary<string,string> dictfruitnames = new Dictionary<string,string>();

  dictfruitprices.Add("Apple",16);

  dictfruitprices.Add("Orange",12);

  dictfruitprices.Add("Cherry",18);

  dictfruitprices["Papaya"] = 20;

  dictfruitprices["Grape"] = 6;

  dictfruitnames.Add("Apple","Red");

  dictfruitnames.Add("Mango","Yellow");

  dictfruitnames.Add("Cherry","Red");

  dictfruitnames.Add("Orange","Dark Orange");

  dictfruitnames["Grape"] = "Violet";

  dictfruitnames["Kiwi"] = "Spring Green";

  foreach (var fruitprice1 in dictfruitprices)

  {

  Console.WriteLine($"{fruitprice1.Key}: {fruitprice1.Value}");

  }

  foreach (var fruitcolor1 in dictfruitnames)

  {

  Console.WriteLine($"{fruitcolor1.Key}: {fruitcolor1.Value}");

  }

  dictfruitprices.Remove("Orange");

  dictfruitnames.Remove("Orange");

  foreach (var fruitprice2 in dictfruitprices)

  {

  Console.WriteLine($"{fruitprice2.Key}: {fruitprice2.Value}");

  }

  foreach (var fruitcolor2 in dictfruitnames)

  {

  Console.WriteLine($"{fruitcolor2.Key}: {fruitcolor2.Value}");

  }

  }

  }

  using System;

  using System.Collections.Generic;

  public class CSharpProgram

  {

  public static void Main(string[] arge)

  {

  Dictionary<string,int> dictfruitprices = new Dictionary<string,int>();

  Dictionary<string,string> dictfruitnames = new Dictionary<string,string>();

  dictfruitprices.Add("Apple",16);

  dictfruitprices.Add("Orange",12);

  dictfruitprices.Add("Cherry",18);

  dictfruitprices["Papaya"] = 20;

  dictfruitprices["Grape"] = 6;

  dictfruitnames.Add("Apple","Red");

  dictfruitnames.Add("Mango","Yellow");

  dictfruitnames.Add("Cherry","Red");

  dictfruitnames.Add("Orange","Dark Orange");

  dictfruitnames["Grape"] = "Violet";

  dictfruitnames["Kiwi"] = "Spring Green";

  foreach (var fruitprice1 in dictfruitprices)

  {

  Console.WriteLine($"{fruitprice1.Key}: {fruitprice1.Value}");

  }

  foreach (var fruitcolor1 in dictfruitnames)

  {

  Console.WriteLine($"{fruitcolor1.Key}: {fruitcolor1.Value}");

  }

  dictfruitprices.Remove("Orange");

  dictfruitnames.Remove("Orange");

  foreach (var fruitprice2 in dictfruitprices)

  {

  Console.WriteLine($"{fruitprice2.Key}: {fruitprice2.Value}");

  }

  foreach (var fruitcolor2 in dictfruitnames)

  {

  Console.WriteLine($"{fruitcolor2.Key}: {fruitcolor2.Value}");

  }

  }

  }

  
  
  

  Output

  Apple: 16

  Orange: 12

  Cherry: 18

  Papaya: 20

  Grape: 6

  Apple: Red

  Mango: Yellow

  Cherry: Red

  Orange: Dark Orange

  Grape: Violet

  Kiwi: Spring Green

  Apple: 16

  Cherry: 18

  Papaya: 20

  Grape: 6

  Apple: Red

  Mango: Yellow

  Cherry: Red

  Grape: Violet

  Kiwi: Spring Green

Summary

Dictionary is collection of Key-Value pairs. In Key-Value pairs, each key must be unique. Dictionary can store specific type (int, float, string, bool) of data.