C # collection class: arraylist, stringcollection, hashtable, list

1. array set
In fact, this concept is already included in the array section. In fact, the array set is new int [2];
Http://msdn.microsoft.com/zh-cn/library/57yac89c (vs.80). aspx
2. arraylist
The difference between arraylist and array: http://msdn.microsoft.com/zh-cn/library/41107z8a (vs.80). aspx
Instance:

Using... system;
Using system. Collections. Generic;
Using system. LINQ;
Using system. text;
Using system. collections;

Namespace CSHARP
...{
Public class testarraylist
...{
Public testarraylist ()
...{
// Create an empty arraylist, and add some elements.
Arraylist stringlist = new arraylist ();

Stringlist. Add ("");
Stringlist. Add ("ABC ");
Stringlist. Add ("abcdef ");
Stringlist. Add ("abcdefg ");
Stringlist. Add (20 );

// Index or array subscript is a number, so no name is required.
Console. writeline ("element... {0} is \" {1} \ "", 2, stringlist [2]);

// Assign a value to the element whose subscript is 2
Stringlist [2] = "ABCD ";
Console. writeline ("element... {0} is \" {1} \ "", 2, stringlist [2]);

// Output the total element elements of the stringlist
Console. writeline ("number of elements in the list:... {0 }",
Stringlist. Count );

Try
...{
// Array subscript ranges from 0 to count-1. If you try to output a subscript smaller than 0 or greater than or equal to count, an exception is thrown.
Console. writeline ("element... {0} is \" {1 }\"",
Stringlist. Count, stringlist [stringlist. Count]);
}
Catch (argumentoutofrangeexception aoore)
...{
Console. writeline ("stringlist (... {0}) is out of range (out of bounds ).",
Stringlist. Count );
}

// You cannot use this method to add elements. You can only use stringlist. Add ("AA") to add elements.
Try
...{
Stringlist [stringlist. Count] = "42 ";
}
Catch (argumentoutofrangeexception aoore)
...{
Console. writeline ("stringlist (... {0}) is out of range (out of bounds ).",
Stringlist. Count );
}

Console. writeline ();
// Use for For Loop
For (INT I = 0; I <stringlist. Count; I ++)
...{
Console. writeline ("element... {0} is \" {1} \ "", I,
Stringlist [I]);
}

Console. writeline ();
// Use foreach For Loop
Foreach (Object o in stringlist)
...{
Console. writeline (O );
}

Console. Readline ();
}
}
}

The stringcollection is similar to arraylist, but stringcollection can only receive character types.
Official Address: http://msdn.microsoft.com/zh-cn/library/system.collections.specialized.stringcollection (vs.80). aspx

3. List <t>, which is the most commonly used one.
Http://msdn.microsoft.com/zh-cn/library/6sh2ey19 (vs.80). aspx
This is actually an example of combining generics with arrays.

Using... system;
Using system. Collections. Generic;
Using system. LINQ;
Using system. text;

Namespace CSHARP
...{
Public class testlist
...{
// Default constructor
Public testlist ()
...{
// Declaration syntax. In other words, it defines the syntax of the objapplelist-set variable.
List <Apple> objapplelist = new list <Apple> ();

// Define three apple instances (also called objects)
Apple objapple1 = new Apple ();
Objapple1.color = "red ";
Objapple1.weight = 10;

Apple objapple2 = new Apple ();
Objapple2.color = "green ";
Objapple2.weight = 12;

Apple objapple3 = new Apple ();
Objapple3.color = "black ";
Objapple3.weight = 8;

// Add the three apple instances to the objapplelist file.

Objapplelist. Add (objapple1 );
Objapplelist. Add (objapple2 );
Objapplelist. Add (objapple3 );

// Traverse the objapplelist set.
Foreach (Apple o in objapplelist)
...{
Console. writeline ("color is... {0}, weight is {1}", O. Color, O. weight );
}

// Total number:
Console. writeline ("the total number of objapplelist files is:... {0}", objapplelist. Count );

Console. Readline ();
}
}

Public class Apple
...{
// Define Fields
Private string _ color = "";
Private decimal _ Weight = 0;

// Define the attribute corresponding to the field
Public String color
...{
Get... {return _ color ;}
Set... {_ color = value;} // The value here is the C # keyword. Indicates the value passed out.
}

Public decimal weight
...{
Get... {return _ weight ;}
Set... {_ Weight = value ;}
}
}
}

Here: List <Apple> objapplelist = new list <Apple> (); in fact, we can use arrays, for example, Apple [] objaapparray = new Apple [3]; however, the array size is fixed. Cannot be added dynamically.
Why not use arraylist here? In principle, arraylist can also be used, for example:

Arraylist obapplearraylist = new arraylist ();
Obapplearraylist. Add (objapple1 );
Obapplearraylist. Add (objapple2 );
Obapplearraylist. Add (objapple2 );

The purpose of the arraylist we don't need is to ensure type security. Because at this time, you can also obapplearraylist. Add ("string");, obapplearraylist. Add ("Heihei");, so that the elements of obapplearraylist are not simply Apple classes.
List <t>.

4. hashtable,
Official Address: http://msdn.microsoft.com/zh-cn/library/system.collections.hashtable (vs.80). aspx
Instance:

Using... system;
Using system. Collections. Generic;
Using system. LINQ;
Using system. text;
Using system. collections;

Namespace CSHARP
...{
Public class testhashtable
...{
Public testhashtable ()
...{
Hashtable objhashtable = new hashtable ();

// It should be noted that the add here is a bit different from the arraylist. here we need to specify two values: Key and value.
// And must all be objects
Objhashtable. Add ("key", "value ");
Objhashtable. Add (1, 2 );
Objhashtable. Add (2.1, 3.2 );

// Obtain all keys
Icollection keys = objhashtable. Keys;
Foreach (Object key in keys)
...{
Console. writeline ("key is... {0}, values is {1}", key, objhashtable [Key]);
}

Console. writeline ();

// Use another Traversal method:
Foreach (dictionaryentry de in objhashtable)
...{
Console. writeline ("key is... {0}, values is {1}", De. Key, De. value );
}

Console. Readline ();
}
}
}