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Now let's look at the composite control itself. Composite controls are implemented using two independent VB source files: Composite. VB and checkevent. VB.

[Composite. VB]

Imports system Imports system. Web Imports system. Web. UI Imports system. Web. UI. webcontrols Imports system. xml Imports system. Collections Namespace customcontrols Public class Composite Inherits Control Implements inamingcontainer Private _ filename as string = "bad_words.xml" Private label as label Private box1 as textbox Public property filename () as string Get Return _ filename End get Set _ Filename = Value End set End Property 'Use the text content submitted by the user as the input parameter. If the content submitted by the user contains offensive words, ', The modified version is returned, 'Otherwise, the original text is directly returned. Public Function checkstring (inputstring as string) as string Dim alwordlist as new arraylist Dim xmldocpath as string = mappathsecure ("bad_words.xml ") Dim xmlreader as xmltextreader = new xmltextreader (xmldocpath) Dim element as string Dim output as string Dim asterisks as string = "*************************" 'Read the XML file that defines offensive words into an arraylist While (xmlreader. Read ()) If xmlreader. nodetype = xmlnodetype. Text then Alwordlist. Add (xmlreader. value) End if End while Xmlreader. Close () 'Check the text content submitted by the user and replace the offensive words with an appropriate number of asterisks. For each element in alwordlist Inputstring = inputstring. Replace (element, Asterisks. substring (1, (element. Length ))) Next Return inputstring End Function Public property text () as string Get 'This method first checks the current value of the childcontrolscreated attribute. If the value is false, 'Then the createchildcontrols method is called. Ensurechildcontrols () Return label. Text End get Set Ensurechildcontrols () Label. Text = Value End set End Property Public event check as checkeventhandler Protected overridable sub oncheck (Ce as checkeventargs) Raiseevent check (Me, Ce) End sub 'Create a child control of the Composite Control Protected overrides sub createchildcontrols () Controls. Add (New literalcontrol (" 'Text input box Dim box1 as new Textbox () Box1.text = "" Controls. Add (box1) Controls. Add (New literalcontrol (" 'Button Dim button1 as new button () Button1.text = "Submit" Controls. Add (New literalcontrol ("<br> ")) Controls. Add (button1) 'Add an event handle to the newly created Button Object Addhandler button1.click, addressof me. buttonclicked Controls. Add (New literalcontrol ("<br> ")) Label = new label () Label. Height = unit. pixel (50) Label. width = unit. pixel (500) Label. Text = "" Controls. Add (Label) End sub Protected overrides sub onprerender (E as eventargs) Ctype (Controls (1), textbox). Text = "" End sub Private sub buttonclicked (sender as [object], e as eventargs) Oncheck (New checkeventargs (ctype (Controls (1), textbox). Text, Checkstring (ctype (Controls (1), textbox). Text ))) End sub End Class End namespace

The main tasks of the code above are:

(1) first, import the necessary namespace and declare the namespace to which the current class belongs.

(2) define the subject of composite. Composite inherits from the most basic control class, and also implements the inamingcontainer interface. The inamingcontainer interface allows the composite control to forward events to its button subcontrol.

(3) Use the createchildcontrols method (instead of oninit or constructor) to create a child control.

(4) The composite control does not display the Click Event of the button subcontrol. Instead, it processes the Click Event and throws the Custom Event check.

The custom Composite Control exposes the following common attributes: text, that is, the text attribute value of the label sub-control; filename, which allows you to obtain and set the name of an XML file that defines an aggressive word.

The main checking function of the callback is implemented by the checkstring method. Its input parameter is a text string. The checkstring method reads the disabled words from the XML file, puts them into an array list (arraylist), and checks whether the specified string contains the disabled words. All "aggressive" words will be replaced by an appropriate number.

Deleonprerender clears the text of the text box subcontrol.

When the user clicks the button, buttonclicked starts execution. Buttonclicked calls the oncheck sub-process and passes in appropriate parameters (a newly created checkeventargs object, and the parameters for creating the checkeventargs object are pre-check and post-check texts ). Oncheck then triggers an event, which is processed by the Code on the. ASPX page.

[Checkevent. VB]

'The code that contains the Custom Event Data class checkeventargs. 'Also defines the event handle of the check event Imports system Namespace customcontrols Public class checkeventargs Inherits eventargs Private _ match as Boolean = false Public sub new (string1 as string, string2 as string) If string1 = string2 then _ Match = true End if End sub Public readonly property match () as Boolean Get Return _ match End get End Property End Class Public Delegate sub checkeventhandler (sender as object, Ce as checkeventargs) End namespace

The constructor of checkeventargs is two strings, and the matching tag _ match is set based on the value of the string. In addition, the Code above defines the checkeventhandler event handle.

After writing the above Code, if you have not installed the IDE, run the following command to compile it:

Vbc/T: Library/out:./bin/customcontrols. dll/R: system. dll/R: system. Web. dll /R: system. Drawing. dll/R: system. Data. dll/R: system. xml. dll *. VB

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