A detailed description of the use of dictionary in C #

1. To use the dictionary collection, you need to import the C # generic namespace

System.Collections.Generic//assembly: mscorlib

Description of 2.Dictionary

A mapping from a set of keys (key) to a set of values (value), each of which is composed of a value and its associated key

Any key must be unique

The key cannot be a null reference null (Nothing in VB), and if the value is a reference type, a null value can be

Key and value can be of any type (String,int,custom class, etc.)

3.Dictionary common usage: type of key is int, type of value is string for example

Create and initialize

Dictionary<int,string> mydictionary=new dictionary<int,string> ();

adding elements

Mydictionary.add (1, "C #"), Mydictionary.add (2, "C + +"), Mydictionary.add (3, "ASP"), Mydictionary.add (4, "MVC");

Find elements by key

if (Mydictionary.containskey (1)) {Console.WriteLine ("Key:{0},value:{1}", "1", mydictionary[1]);}

Traversing elements through KeyValuePair

foreach (keyvaluepair<int,string> kvp in mydictionary) {    Console.WriteLine ("Key = {0}, Value = {1}", kvp. Key, kvp. Value);}

Traverse key Keys Property only

Dictionary<int,string>. KeyCollection KeyCol = Mydictionary.keys;foreach (Intkeyinkeycol) {Console.WriteLine ("key = {0}", key);}

Traverse only the Value Valus property

Dictionary<int,string>. ValueCollection Valuecol = Mydictionary.values;foreach (Stringvalueinvaluecol) {Console.WriteLine ("value = {0}", value );}

Remove the specified key value from the Remove method

Mydictionary.remove (1), if (Mydictionary.containskey (1)) {Console.WriteLine ("Key:{0},value:{1}", "1", myDictionary[ 1]);} else{    Console.WriteLine ("Does not exist key:1");  }

4. description of other common properties and methods:

 comparer://Gets the IEqualityComparer used to determine whether the keys in the dictionary are equal.  Count://Gets the number of key/value pairs contained in the dictionary.  Item://Gets or sets the value associated with the specified key.  Keys://Gets the collection that contains the keys in the dictionary.  Values://Gets the collection that contains the values in the dictionary.  Add://Adds the specified key and value to the dictionary.  Clear://Remove all keys and values from the dictionary.  ContainsKey://Determines whether the dictionary contains the specified key.               Containsvalue://Determines whether the dictionary contains a specific value.  GetEnumerator://Returns an enumerator that iterates through the dictionary. GetType://Gets the Type of the current instance. (Inherit from Object.)  Remove://Removes the value of the specified key from the dictionary. ToString://Returns a String that represents the current object. (Inherit from Object.) ) TryGetValue://Gets the value associated with the specified key.