The use of the C#Dictionary

The primary purpose of Dictionary in C# is to provide fast part-time-based element lookups. T he structure of The Dictionary is generally like this: Dictionary-lt; B efore you can use Dictionary, you must declare its key type and value type.

To make it easier and more effective to learn the C-tutorial, we recommend that you take the C-micro-course

To use the Dictionary collection, you need to import the C-generic namespace

System.Collections.Generic (Assembly: mscorlib)

Description of Dictionary

1, from a set of keys (Key) to a set of values (Value) mapping, each addition is composed of a value and its associated keys

2. Any key must be unique

3, the key can not be an empty reference null (nothing in VB), if the value is a reference type, you can be an empty value

4, Key and Value can be any type (string, int, custom class, etc.)

Dictionary is commonly used: the type of key is int, the type of value is stringing, for example

1, creation and initialization

Dictionary<int,string>myDictionary=newDictionary<int,string>();

2, add elements

myDictionary.Add(1,"C#");
myDictionary.Add(2,"C++");
myDictionary.Add(3,"ASP.NET");
myDictionary.Add(4,"MVC");

3, find elements through Key

if(myDictionary.ContainsKey(1))
{
Console.WriteLine("Key:{0},Value:{1}","1", myDictionary[1]);
 }

4, traversing elements through KeyValuePair

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

5, only traversing the key Keys property

Dictionary<int,string>.KeyCollection keyCol=myDictionary.Keys;
foreach(intkeyinkeyCol)
...{
Console.WriteLine("Key = {0}", key);
}

6, only traversing the value Valus properties

Dictionary<int,string>.ValueCollection valueCol=myDictionary.Values;
foreach(stringvalueinvalueCol)
...{
Console.WriteLine("Value = {0}", value);
}

7, through the Remove method to remove the specified key value

myDictionary.Remove(1);
if(myDictionary.ContainsKey(1))
...{
　　Console.WriteLine("Key:{0},Value:{1}","1", myDictionary[1]);
}
else
{
Console.WriteLine("不存在 Key : 1"); 
 }

Description of other common properties and methods: