[C # Use the backend to dynamically load data] winform "defense against brute-force attacks"

Nonsense: recently encountered projects found that when winform obtains a large amount of data, the interface is suspended and the experience is very poor. As a tester, we have the obligation and responsibility to raise bugs. Every test is faced with an interface that has been stuck for more than five seconds. It is really a kind of torture and a kind of suicide. You can use multiple threads to process data, or use the background to obtain data. Multi-threading can solve the problem, but it may be more complicated to dynamically load data. Because of multithreading, You need to execute a thread to update the data. The intelligence is not high enough. When using the background, you can report the obtained data at any time, which can be precise to a specific item, and it is easy to use, because it has been encapsulated.

Class used: backgroundworker under using system. componentmodel;

This class has four important methods: dowork, progresschanged, runworkercompleted, runworkerasync, two important attributes workersuppscanscancellation, workerreportsprogress

Method:

1. dowork: indicates what to do with the background. When binding time, the input parameter is the method name.

2. progresschanged: What should I do in the background when the progress changes, and the parameter passed in when the binding time is the method name

3. runworkercompleted

4. runworkerasync: enables backend and starts running in the background.

Attribute:

1. workersuppscanscancellation: whether asynchronous cancellation is supported

2. workerreportsprogress: whether to report progress updates. This attribute is very important and must be enabled to report progress.

The following example shows how to dynamically load data in the background:

Let's first make a simple interface

 

The required function is: Click start to start listing the file names under drive C one by one, and the progress bar shows the progress. The first method is to add the file name to the listview. In this way, thread. Sleep ( 500 ), Sleep for 0.5 seconds: View code

 1    Public   Void Add ( Object Sender, doworkeventargs E)
 2 {
 3 Directoryinfo di = New Directoryinfo ( @" C :/  " );
 4               Foreach (Fileinfo item In Di. getfiles ())
 5 {
 6 Listviewitem lvt = New Listviewitem (); // use listviewitem to store the information of the obtained object.
 7 Lvt. Text = item. fullname;
 8 Lvt. subitems. Add (datetime. Now. tolongtimestring ());
 9 Thread. Sleep ( 500 );
 10 Bw. reportprogress (listview1.items. Count, lvt); // report the current progress and obtain the information of the file and the file.
 11 }
 12             
 13 }

Method 2: report the progress after obtaining the progress: View code

  1   Public   void  progress ( Object  sender, progresschangedeventargs e) 
  2 {< br>  3  progressbar1.value = E. progresspercentage; ///   obtain the objects, used to change the progress of the progress bar   
   4    listviewitem Lv = E. userstate  as  listviewitem; 
  5  listview1.items. add (LV); ///   Add the latest file information to listview   
   6   }

The third method looks like a chicken in this example. The event is executed after the background is completed:

 
1Public VoidEnd (ObjectSender, asynccompletedeventargs E)
2{
3Progressbar1.value =0;//Progress bar cleared 0
4 }
 

Finally, write the following method in the double-click event: View code

 1     Private   Void Button#click (Object Sender, eventargs E)
 2 {
 3 Directoryinfo di = New Directoryinfo ( @"  C :/  " );
 4 Fileinfo [] Fi = Di. getfiles ();
 5 Progressbar1.maximum = Fi. Length- 1 ; // Set the maximum value of the progress bar  
  6    Bw. workersuppscanscancellation = True ;
 7 Bw. workerreportsprogress = True ;
 8 Bw. dowork + = New Doworkeventhandler (ADD ); //  Bind event  
  9   Bw. progresschanged + = New Progresschangedeventhandler (Progress );
 10 Bw. runworkercompleted + = New Runworkercompletedeventhandler (end );
 11 Bw. runworkerasync ();
 12 }

Note: When defining three methods in the background, the format must be a template. You can run the following results. Obviously, this is what the user needs. If you want to retrieve large data volumes at a time or operate them in a single thread, the experience is very poor. If software is to be recognized, the user experience plays a very important role. Although a software uses a very advanced technology, the user experience is very poor, users often weigh the option that is more convenient.

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