Are you familiar with dictionary and list?

The namespace system. Collections. Generic has two very important and common generic collection classes, which are dictionary <tkey, tvalue> dictionary and list <t> list.The dictionary is usually used to save the data of key/value pairs, while the List list is used to save the list of strong types of objects that can be accessed through the index.The following is a summary.CodeTo demonstrate how to initialize, add, modify, delete, and traverse elements.

Dictionary <tkey, tvalue> dictionary

The Code is as follows:

 Namespace Dictionarydemo1
{
 Class Program
{
 Static   Void Main ( String [] ARGs)
{
//  Create a dictionary <tkey, tvalue> Object  
 Dictionary < String , String > Openwith = New Dictionary < String , String > ();

 //  There are two methods to add elements to an object. Note: The keys in the dictionary cannot be repeated, but the values can be repeated.
  //  Method 1: Use the add () method of the object  
 Openwith. Add ( "  Txt  " , "  Notepad.exe  " );
Openwith. Add ( "  BMP  " , "  Paint.exe  " );
Openwith. Add ( "  DiB " , "  Paint.exe  " );
Openwith. Add ( "  RTF  " , "  Wordpad.exe  " );

 //  Method 2: Use Indexer
  //  Openwith ["TXT"] = "notepad.exe ";
 //  Openwith ["BMP"] = "paint.exe ";
  //  Openwith ["Dib"] = "paint.exe ";
  //  Openwith ["rtf"] = "wordpad.exe ";

  //  Add an element. Before adding a key, check whether the containskey () method is used.  
              If (! Openwith. containskey ( "  HT  " ))
{
Openwith. Add ("  HT  " , "  Hypertrm.exe  " ); //  Or openwith ["ht"] = "hypertrm.exe ";  
 Console. writeline ( "  Element Added! Key = {0}, value = {1}  " , "  HT  " , Openwith ["  HT  " ]);
}

 //  Delete an element and use the remove () method.  
              If (Openwith. containskey ( "  RTF  " ))
{
Openwith. Remove ( "  RTF  " );
Console. writeline ( "  Element deleted! The key is RTF.  " );
}

 If (! Openwith. containskey ( "  RTF  " ))
{
Console. writeline ( "  The key = \ "RTF \" element cannot be found!  " );
}

//  Modify the element and use the indexer.  
              If (Openwith. containskey ( "  Txt  " ))
{
Openwith [ "  Txt  " ] = "  Notepadupdate.exe  " ;
Console. writeline ("  Element modified! Key = {0}, value = {1}  " , "  Txt  " , Openwith [ "  Txt  " ]);
}

 //  This class implements the ienumerable interface, so you can use the foreach statement. Note that the element type is keyvaluepair (of tkey, tvalue)  
              Foreach (Keyvaluepair <String , String > KVp In Openwith)
{
Console. writeline ( "  Key = {0}, value = {1}  " , KVp. Key, kVp. value );
}

Console. writeline ( "  Element traversal is completed!  " );
Console. readkey ();
}
}
}

ProgramOutput result:

List <t> List

The Code is as follows:

 Namespace Listdemo1
{
 Class Program
{
 Static   Void Main ( String [] ARGs)
{
 //  Create a list <t> list object  
 List <String > Din1_urs = New List < String > ();

 //  Add an element to the list (or initialization). Note that the indexer cannot be used during initialization because the list is empty before adding an element.  
 Dinosaurs. Add ( "  Tyrannosaurus  " );
Dinosaurs. Add ( "  Amargasaurus  " );
Dinosaurs. Add ( "  Mamenchisaurus  " );
Dinosaurs. Add ( "  Deinonychus  " );
Dinosaurs. Add ( "  Compsognathus  " );

 //  An important attribute  
 Console. writeline ("  Number of elements in the list: {0}  " , Din1_urs. Count ); //  Obtains the number of actually contained elements in the list.


  //  Insert element, using the insert () method  
 Din1_urs. insert ( 2 , "  Compsognathus  " ); //  Insert the element to the specified index.  
 Console. writeline ( "  Insert element {0} At index 2}  " , Din1_urs [ 2 ]);

 //  Delete an element and use the remove () method.  
 Dinosaurs. Remove ( "  Compsognathus  " ); //  Removes the first matching item of a specific object from the list.  
 Console. writeline ("  Delete the first element named compsognathus!  " );

 //  Modify the element and use the indexer.  
 Din1_urs [ 0 ] = "  Tyrannosaurusupdate  " ;
Console. writeline ( "  Successfully modified the element whose index is 0!  " );

//  Traverse elements using the foreach statement. The element type is string.  
              Foreach ( String Dinosaur In Dinosaurs)
{
Console. writeline (dinw.ur );
}

Console. writeline ( "  Element traversal is completed!  " );
Console. readkey ();
}
}
}

Program output result: