C # Cross-thread controls,

C # Cross-thread controls,

The Invoke and BeginInvoke methods are always used when you look at other people's code. Although you have a general understanding of what it means, it cannot be used very well. I checked a lot of information online, I happened to have reposted a blog post during my studies:

C # differences between Invoke and BeginInvoke

The blog post focuses on some theoretical knowledge. This article introduces several common problems:

On the. net platform, Winform and wpf prohibit cross-thread direct access to controls. Therefore, the asynchronous method is used when controls must be accessed across threads.

 

1. Cross-thread access control in the winform project:

Compile a Winform small instance: In a winform project, sometimes to display the running status of the system to the Form in real time, add a RichTextbox Control to display the system running logs in real time. In this example, logs are written to the RichTextbox Control in the form of strings. Because logs are displayed in real time, cross-thread input is involved.

Private delegate void setRichTexBox (string s); public void setText (string txt) {if (this. t_revmsg.InvokeRequired) // wait for asynchronous {setRichTexBox fc = new setRichTexBox (Set); this. invoke (fc, new object [] {txt});} else {this. t_revmsg.AppendText (txt );}}
Private void Set (string txt) {t_revmsg.AppendText (txt );}

When the InvokeRequired value of the control is true, it indicates that a thread that does not belong to its creation needs to access it. At this time, it needs to be operated asynchronously.

 

2. Cross-thread access control in the wpf project:

Add a button control and textbox Control to the page of wpf, and click "button" to add the content in the textbox Control.

private void button2_Click(object sender, RoutedEventArgs e)        {            this.textBox1.Dispatcher.Invoke(new WriteDelegate(WriteMethod), "asdf");        }        private delegate void WriteDelegate(string str);        private void WriteMethod(string str)        {            this.textBox1.AppendText(str);        }

 

3. Cross-thread acquisition of content in the textbox Control in the wpf Project

This example provides the following functions: click the button control to enable the socket listening service. The listening port needs to be obtained from textbox In the UI interface, because it is not accessed by the thread that created it, so there is a Dispatcher. Invoke asynchronous operation. Supplement: When the listener is enabled, a while (true) endless loop exists. Putting it directly into the main thread will cause the thread to fail, the solution is to enable a new thread to enable the listener.

private void button1_Click(object sender, RoutedEventArgs e)        {            Thread thread = new Thread(new ThreadStart(StartServer));            thread.Start();        }public void StartServer()        {            int port = Convert.ToInt32(GetText(this.tbPort));            ServerSocket serverSocket = new ServerSocket(port);            serverSocket.Start();        }private delegate string GetTextHandle(Control control);        private string GetText(Control control)        {            if (this.Dispatcher.Thread != System.Threading.Thread.CurrentThread)            {                return (string)this.Dispatcher.Invoke(new GetTextHandle(this.GetText), control);            }            else            {                if (control.GetType() == typeof(TextBox))                {                    return ((TextBox)control).Text;                }                else                {                    return string.Empty;                }            }        }

 

Summary:

From the above several instances, we can see that the cross-thread call requires the use of Invoke and BeginInvoke (not used for the time being). In some systems where the requirements are not very strict, they are considered universal for the moment. (Do not know, right? Hope you have a finger)

These are the only common problems you have encountered so far. Please try again later.

A simple program of C language Bubble Sorting

Main ()
{
Int I, j, temp;
Int a [10];
For (I = 0; I <10; I ++)
Scanf ("% d,", & a [I]);
For (j = 0; j <= 9; j ++)
{For (I = 0; I <10-j; I ++)
If (a [I]> a [I + 1])
{Temp = a [I];
A [I] = a [I + 1];
A [I + 1] = temp ;}
}
For (I = 1; I <11; I ++)
Printf ("% 5d,", a [I]);
Printf ("\ n ");
}

--------------
Bubble Algorithm
Algorithm Analysis and Improvement of Bubble Sorting
The basic idea of exchanging sorting is to compare the keywords of the records to be sorted in pairs. If the order of the two records is the opposite, the two records are exchanged until there is no reverse order record.
The basic concepts of application exchange sorting include Bubble sorting and quick sorting.

Bubble Sorting

1. Sorting Method
Vertically arrange the sorted record array R [1. n]. Each record R is considered as a bubble with the weight of R. key. According to the principle that a Light Bubble cannot be under a heavy bubble, scan the array R from the bottom up: Any Light Bubble scanned to a violation of this principle will make it "float" up ". This is repeated until the last two bubbles are light and heavy.
(1) initial
R [1. n] is an unordered area.

(2) First scan
The weights of two adjacent bubbles are compared from the bottom of the unordered area to the top. If the light bubbles are found to be in the lower and severe bubbles, the positions of the two bubbles are exchanged. That is, compare (R [n], R [n-1]), (R [n-1], R [N-2]),…, (R [2], R [1]); for each pair of bubbles (R [j + 1], R [j]), if R [j + 1]. key <R [j]. key, then the contents of R [j + 1] and R [j] are exchanged.
When the first scan is complete, the "lightest" bubble floated to the top of the interval, that is, the record with the smallest keyword is placed on the highest position R [1.

(3) second scan
Scan R [2. n]. When scanning is completed, the "light" bubble floated to the R [2] position ......
Finally, the sequential area R [1. n] can be obtained through n-1 scanning.
Note:
During the I-trip scan, R [1 .. I-1] and R [I.. n] are the current sequential and disordered areas, respectively. The scan continues from the bottom of the unordered area to the top of the area. When scanning is completed, the shortest bubbles in the area float to the top position R. The result is that R [1. I] is changed to a new ordered area.

2. Bubble sorting process example
Bubble Sorting of files whose keyword sequence is 49 38 65 97 76 13 27 49

3. Sorting Algorithm
(1) Analysis
Because each sort adds a bubble to the ordered area, there are n-1 bubbles in the ordered area after N-1 sort, in the disordered area, the bubble weight is always greater than or equal to the bubble weight in the ordered area. Therefore, the entire Bubble sorting process requires at most n-1 sorting.
If no bubble position exchange is found in a sorting, it means that all bubbles in the unordered area to be sorted meet the principle of being light and heavy. Therefore, the Bubble sorting process can be terminated after this sorting. Therefore, in the following algorithm, a Boolean exchange is introduced, which is set to FALSE before each sort starts. If an exchange occurs during the sorting process, set it to TRUE. Check exchange at the end of sorting. If exchange has not occurred, terminate the algorithm and no longer perform the next sorting.

(2) specific algorithms
Void BubbleSort (SeqList R)
{// R (l. n) is the file to be sorted. It uses bottom-up scanning to perform Bubble Sorting on R.
Int I, j;
Boolean exchange; // exchange flag
For (I = 1; I <G id = "1">

A simple program of C language Bubble Sorting

Main ()
{
Int I, j, temp;
Int a [10];
For (I = 0; I <10; I ++)
Scanf ("% d,", & a [I]);
For (j = 0; j <= 9; j ++)
{For (I = 0; I <10-j; I ++)
If (a [I]> a [I + 1])
{Temp = a [I];
A [I] = a [I + 1];
A [I + 1] = temp ;}
}
For (I = 1; I <11; I ++)
Printf ("% 5d,", a [I]);
Printf ("\ n ");
}

--------------
Bubble Algorithm
Algorithm Analysis and Improvement of Bubble Sorting
The basic idea of exchanging sorting is to compare the keywords of the records to be sorted in pairs. If the order of the two records is the opposite, the two records are exchanged until there is no reverse order record.
The basic concepts of application exchange sorting include Bubble sorting and quick sorting.

Bubble Sorting

1. Sorting Method
Vertically arrange the sorted record array R [1. n]. Each record R is considered as a bubble with the weight of R. key. According to the principle that a Light Bubble cannot be under a heavy bubble, scan the array R from the bottom up: Any Light Bubble scanned to a violation of this principle will make it "float" up ". This is repeated until the last two bubbles are light and heavy.
(1) initial
R [1. n] is an unordered area.

(2) First scan
The weights of two adjacent bubbles are compared from the bottom of the unordered area to the top. If the light bubbles are found to be in the lower and severe bubbles, the positions of the two bubbles are exchanged. That is, compare (R [n], R [n-1]), (R [n-1], R [N-2]),…, (R [2], R [1]); for each pair of bubbles (R [j + 1], R [j]), if R [j + 1]. key <R [j]. key, then the contents of R [j + 1] and R [j] are exchanged.
When the first scan is complete, the "lightest" bubble floated to the top of the interval, that is, the record with the smallest keyword is placed on the highest position R [1.

(3) second scan
Scan R [2. n]. When scanning is completed, the "light" bubble floated to the R [2] position ......
Finally, the sequential area R [1. n] can be obtained through n-1 scanning.
Note:
During the I-trip scan, R [1 .. I-1] and R [I.. n] are the current sequential and disordered areas, respectively. The scan continues from the bottom of the unordered area to the top of the area. When scanning is completed, the shortest bubbles in the area float to the top position R. The result is that R [1. I] is changed to a new ordered area.

2. Bubble sorting process example
Bubble Sorting of files whose keyword sequence is 49 38 65 97 76 13 27 49

3. Sorting Algorithm
(1) Analysis
Because each sort adds a bubble to the ordered area, there are n-1 bubbles in the ordered area after N-1 sort, in the disordered area, the bubble weight is always greater than or equal to the bubble weight in the ordered area. Therefore, the entire Bubble sorting process requires at most n-1 sorting.
If no bubble position exchange is found in a sorting, it means that all bubbles in the unordered area to be sorted meet the principle of being light and heavy. Therefore, the Bubble sorting process can be terminated after this sorting. Therefore, in the following algorithm, a Boolean exchange is introduced, which is set to FALSE before each sort starts. If an exchange occurs during the sorting process, set it to TRUE. Check exchange at the end of sorting. If exchange has not occurred, terminate the algorithm and no longer perform the next sorting.

(2) specific algorithms
Void BubbleSort (SeqList R)
{// R (l. n) is the file to be sorted. It uses bottom-up scanning to perform Bubble Sorting on R.
Int I, j;
Boolean exchange; // exchange flag
For (I = 1; I <G id = "1">