ASP. NET startkit timetracker (custom collection class sorting () method)

Many custom collection classes are defined in ASP. NET startkit timetracker.
For example:
Userscollection
Timeentriescollection
And so on.

They are all subclasses of the arraylist class.

For example:
Timeentriescollection stores custom timeentry classes

These custom collection classes all implement the sorting method sort

First read the section I wroteCode:

Using System;
Using System. collections;

Namespace Arraylistsort
{
Class Class1
{
[Stathread]
Static   Void Main ( String [] ARGs)
{
Arraylist = New Arraylist ( 8 );
A. Add ( 111 );
A. Add ( 2 );

A. Sort ();

Ienumerator = A. getenumerator ();
While (Ienumerator. movenext ())
{
Console. writeline (ienumerator. Current. tostring ());
}

Arraylist B = New Arraylist ( 8 );
B. Add ( New Class2 ( " Wo " ));
B. Add ( New Class2 ( " AI " ));
B. Add ( New Class2 ( " I " ));

B. Sort ();

Ienumerator iienumerator = B. getenumerator ();
While (Iienumerator. movenext ())
{
Console. writeline (class2) iienumerator. Current). );
}

Console. Readline ();
}
}

Public   Class Class2
{

Public Class2 ( String Str)
{
This.=STR;
}

String A;

Public   String A
{< br> Get
{< br> return A;
}
}

}


}

The running result is

The sorting result of A is displayed.
An error occurred while sorting B.

Why is such a result?
Arraylist's sort method uses the icomparable API for sorting.
This means that each object in the arraylist needs to implement the icomparable interface.
Int, string, and other system-defined types have implemented the icomparable interface.
A. Sort () method runs correctly
B. Sort (); an error occurs because the icomparable interface is not implemented.

Modify the class2 code,ProgramYou can run it correctly.

Public   Class Class2: icomparable
{

Public Class2 ( String Str)
{
This.=STR;
}

String A;

Public   String A
{< br> Get
{< br> return A;
}
}


Public   Int Compareto ( Object O)
{
Return This. A. compareto (class2) O). );
}

}

In fact, there is another way to achieve sorting
Use sort (icomparer)
Define the class implementation interface system. Collections. icomparer
The Code is as follows:

Public   Class Class2_sort: system. Collections. icomparer
{
// Ascending or not
Bool Isasc;

// The default sorting method is ascending.
Public Class2_sort ()
{
Isasc=True;
}

Public Class2_sort ( Bool B)
{
Isasc=B;
}

Public Int Compare ( Object X, Object Y)
{
If (Isasc)
{
//Ascending
Return(Class2) x). A. compareto (class2) Y). );
}
Else
{
//Descending Order
Return(Class2) Y). A. compareto (class2) x). );
}
}
}

B. Sort (New class2_sort (false ));
You can sort data in descending order.

I personally think this method is highly flexible.
Recommended

Summary:
1. to sort the arrays of your own objects, implement the icomparable interface on this object.
A compareto method must be defined in the object to specify the method for comparing the object.
2. to define a specific method for comparing objects, create a class that implements the icomparer interface.
This class must contain a compare method that accepts the two objects to be compared.
It helps you understand how you want to compare objects and what objects are allowed to use the defined interfaces.

 

I hope the Knowledge mentioned above will prompt you.
Of course, you are welcome to contact us and correct us.

Author: aierong
Blog: http://www.cnblogs.com/aierong
Email: aierong@126.com