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ControlBuilder Class

Supports the page parser in building a control and the child controls it contains.

Namespace: System.Web.UI
Assembly: System.Web (in system.web.dll)

'Declaration
Public Class ControlBuilder
'Usage
Dim instance As ControlBuilder

public class ControlBuilder
public class ControlBuilder
Not applicable.

By default, every control on a page is associated with a default ControlBuilder class. During parsing, the ASP.NET page framework builds a tree of ControlBuilder objects corresponding to the tree of controls for the page. The ControlBuilder tree is then used to generate page code to create the control tree. In addition to child controls, the ControlBuilder defines the behavior of how the content within control tags is parsed. You can override this default behavior by defining your own custom control builder class. This is done by applying a ControlBuilderAttribute attribute to your control builder class as follows:

[ControlBuilderAttribute(typeof(ControlBuilderType))]

The following code example creates a Table control whose attributes and content are defined at the time the table is built. The following is the command line to use to build the executable.

[Visual Basic]

vbc /r:System.dll /r:System.Web.dll /r:System.Drawing.dll /t:library /out:myWebAppPath/Bin/vb_mycontrolbuilder.dll myControlBuilder.vb

[C#]

csc /t:library /out:myWebAppPath/Bin/cs_mycontrolbuilder.dll myControlBuilder.cs
Imports System
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Collections
Imports System.Drawing
Imports System.Security.Permissions


Namespace CustomControls

    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
    Public Class MyTableCell
        Inherits TableCell
        Implements INamingContainer
    End Class


    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
    Public Class MyCell
        Inherits Control
        Implements INamingContainer
        ' Class Name: MyCell.
        ' Declares the class for the child controls to be included in the control collection.

        Private _id As String
        Private _value As String
        Private _backColor As Color

        Public Property CellID() As String
            Get
                Return _id
            End Get
            Set(ByVal value As String)
                _id = value
            End Set
        End Property

        Public Property Text() As String
            Get
                Return _value
            End Get
            Set(ByVal value As String)
                _value = value
            End Set
        End Property


        Public Property BackColor() As Color
            Get
                Return _backColor
            End Get
            Set(ByVal value As Color)
                _backColor = value
            End Set
        End Property
    End Class

    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _
    Public Class MyControlBuilderVB
        Inherits ControlBuilder

        Public Overrides Function GetChildControlType(ByVal tagName As String, ByVal attribs As IDictionary) As Type

            ' Allows TableRow without "runat=server" attribute to be added to the collection.
            If (String.Compare(tagName, "mycell", True) = 0) Then
                Return GetType(MyCell)
            End If
            Return Nothing
        End Function

        ' Ignores literals between rows.
        Public Overrides Sub AppendLiteralString(ByVal s As String)
            ' Ignores literals between rows.
        End Sub

    End Class

    <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal), ControlBuilderAttribute(GetType(MyControlBuilderVB))> _
        Public Class MyVB_CustomControl
        Inherits Control
        Implements INamingContainer

        ' Class name: MyVB_CustomControl.
        ' Processes the element declarations within a control 
        ' declaration. This builds the actual control.

        ' Custom control to build programmatically.
        Private _table As Table

        Private _cellObjects As New Hashtable()

        ' Variables that must contain the control attributes as defined in the Web page.
        Private _rows As Integer
        Private _columns As Integer
        Private _title As String

        ' Rows property to be used as the attribute name in the Web page.     
        Public Property Rows() As Integer
            Get
                Return _rows
            End Get
            Set(ByVal value As Integer)
                _rows = value
            End Set
        End Property

        ' Columns property to be used as the attribute name in the Web page.

        Public Property Columns() As Integer
            Get
                Return _columns
            End Get
            Set(ByVal value As Integer)
                _columns = value
            End Set
        End Property

        ' Title property to be used as the attribute name in the Web page   
        Public Property Title() As String
            Get
                Return _title
            End Get
            Set(ByVal value As String)
                _title = value
            End Set
        End Property


        Protected Sub createNewRow(ByVal rowNumber As Integer)

            ' Creates a row and adds it to the table.
            Dim row As TableRow

            row = New TableRow()
            _table.Rows.Add(row)

            ' Creates a cell that contains text.
            Dim y As Integer
            For y = 0 To Columns - 1
                appendCell(row, rowNumber, y)
            Next y
        End Sub 'createNewRow


        Protected Sub appendCell(ByVal row As TableRow, ByVal rowNumber As Integer, ByVal cellNumber As Integer)
            Dim cell As TableCell
            Dim textbox As TextBox

            cell = New TableCell()

            textbox = New TextBox()

            cell.Controls.Add(textbox)

            textbox.ID = "r" + rowNumber.ToString() + "c" + cellNumber.ToString()

            ' Checks for the MyCell child object.
            If Not (_cellObjects(textbox.ID) Is Nothing) Then
                Dim cellLookup As MyCell
                cellLookup = CType(_cellObjects(textbox.ID), MyCell)

                textbox.Text = cellLookup.Text
                textbox.BackColor = cellLookup.BackColor

            Else
                textbox.Text = "Row: " + rowNumber.ToString() + " Cell: " + cellNumber.ToString()
            End If

            row.Cells.Add(cell)
        End Sub 'appendCell

        ' Called at runtime when a child object is added to the collection.
        Protected Overrides Sub AddParsedSubObject(ByVal obj As Object)

            Dim cell As MyCell = CType(obj, MyCell)
            If Not (cell Is Nothing) Then
                _cellObjects.Add(cell.CellID, cell)
            End If
        End Sub 'AddParsedSubObject


        Protected Overrides Sub OnPreRender(ByVal e As EventArgs)
            ' Sub name: OnPreRender.
            ' Carries out changes affecting the control state and renders the resulting UI.

            ' Increases the number of rows if needed.
            While _table.Rows.Count < Rows
                createNewRow(_table.Rows.Count)
            End While

            ' Checks that each row has the correct number of columns.
            Dim i As Integer
            For i = 0 To _table.Rows.Count - 1
                While _table.Rows(i).Cells.Count < Columns
                    appendCell(_table.Rows(i), i, _table.Rows(i).Cells.Count)
                End While

                While _table.Rows(i).Cells.Count > Columns
                    _table.Rows(i).Cells.RemoveAt((_table.Rows(i).Cells.Count - 1))
                End While
            Next i
        End Sub 'OnPreRender


        <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
        Protected Overrides Sub CreateChildControls()
            ' Sub name: CreateChildControls.
            ' Adds the Table and the text controls to the control collection. 


            Dim [text] As LiteralControl

            ' Initializes the text control using the Title property.
            [text] = New LiteralControl("<h5>" + Title + "</h5>")
            Controls.Add([text])


            _table = New Table()

            Controls.Add(_table)
        End Sub
    End Class

End Namespace


package CustomControls;
import System.*;
import System.Web.*;
import System.Web.UI.*;
import System.Web.UI.WebControls.*;
import System.Collections.*;
import System.Drawing.*;
import System.Security.Permissions.*;

/** @attribute AspNetHostingPermission(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
 */
public class MyTableCell extends TableCell implements INamingContainer
{
}

/** @attribute AspNetHostingPermission(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
 */
public class MyCell
{
    /*
        Class name: MyCell.
        Declares the class for the child controls to include in the control
        collection.
    */
    private String _id;
    private String _value;
    private Color _backColor;
    
    /** @property 
     */
    public String get_CellID()
    {
        return _id;
    } //get_CellID

    /** @property 
     */
    public void set_CellID(String value)
    {
        _id = value;
    } //set_CellID

    /** @property 
     */
    public String get_Text()
    {
        return _value;
    } //get_Text

    /** @property 
     */
    public void set_Text(String value)
    {
        _value = value;
    } //set_Text

    /** @property 
     */
    public Color get_BackColor()
    {
        return _backColor;
    } //get_BackColor

    /** @property 
     */
    public void set_BackColor(Color value)
    {
        _backColor = value;
    } //set_BackColor
} //MyCell

/** @attribute AspNetHostingPermission(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
 */
public class MyControlBuilder extends ControlBuilder
{
    public Type GetChildControlType(String tagName, IDictionary attribs)
    {
        // Allows TableRow without "runat=server" attribute to be added
        // to the collection.
		if (String.Compare(tagName, "mycell", true) == 0) {
            return MyCell.class.ToType();
        }
        return null;
    }

    public void AppendLiteralString(String s)
    {
        // Ignores literals between rows.
    }
}

/** @attribute ControlBuilderAttribute(MyControlBuilder.class)
 */
/** @attribute AspNetHostingPermission(SecurityAction.InheritanceDemand, Level = AspNetHostingPermissionLevel.Minimal)]
 */
public class MyJSL_CustomControl extends Control implements INamingContainer
{
    /*
        Class name: MyJSL_CustomControl.
        Processes the element declarations within a control declaration. 
        This builds the actual control.
    */
    // Declares the custom control that must be built programmatically.
    private Table _table;
    private String _title;
    private int _rows;
    private int _columns;
    private Hashtable _cellObjects = new Hashtable();

    // Rows property to be used as the attribute name in the Web page.  
    /** @property 
     */
    public int get_Rows()
    {
        return _rows;
    }

    /** @property 
     */
    public void set_Rows(int value)
    {
        _rows = value;
    }

    // Columns property to be used as the attribute name in the Web page.
    /** @property 
     */
    public int get_Columns()
    {
        return _columns;
    }

    /** @property 
     */
    public void set_Columns(int value)
    {
        _columns = value;
    }

    // Title property to be used as the attribute name in the Web page.
    /** @property 
     */
    public String get_Title()
    {
        return _title;
    }

    /** @property 
     */
    public void set_Title(String value)
    {
        _title = value;
    }

    protected void CreateNewRow(int rowNumber)
    {
        // Creates a row and adds it to the table.
        TableRow row;
        row = new TableRow();
        _table.get_Rows().Add(row);
        // Creates a cell that contains text.
        for (int y = 0; y < get_Columns(); y++) {
            AppendCell(row, rowNumber, y);
        }
    } //CreateNewRow

    protected void AppendCell(TableRow row, int rowNumber, int cellNumber)
    {
        TableCell cell;
        TextBox textbox;

        cell = new TableCell();
        textbox = new TextBox();
        cell.get_Controls().Add(textbox);
        textbox.set_ID("r" + ((Int32)rowNumber).ToString() + "c"
            + ((Int32)cellNumber).ToString());
        // Checks for the MyCell child object.
        if (_cellObjects.get_Item(textbox.get_ID()) != null) {
            MyCell cellLookup;
            cellLookup = (MyCell)_cellObjects.get_Item(textbox.get_ID());

            textbox.set_Text(cellLookup.get_Text());
            textbox.set_BackColor(cellLookup.get_BackColor());
        }
        else {
            textbox.set_Text("Row: " + ((Int32)rowNumber).ToString() + " Cell: "
                + ((Int32)cellNumber).ToString());
        }

        row.get_Cells().Add(cell);
    }

    // Called at runtime when a child object is added to the collection.  
    protected void AddParsedSubObject(Object obj)
    {
        MyCell cell = (MyCell)obj;
        if (cell != null) {
            _cellObjects.Add(cell.get_CellID(), cell);
        }
    }

    protected void OnPreRender(EventArgs e)
    {
        /*
            Function name: OnPreRender.
            Carries out changes affecting the control state and renders the
            resulting UI.
        */
        // Increases the number of rows if needed.
        while (_table.get_Rows().get_Count() < get_Rows()) {
            CreateNewRow(_table.get_Rows().get_Count());
        }
        // Checks that each row has the correct number of columns.
        for (int i = 0; i < _table.get_Rows().get_Count(); i++) {
            while (_table.get_Rows().get_Item(i).get_Cells().
                get_Count() < get_Columns()) {
                AppendCell(_table.get_Rows().get_Item(i), i,
                    _table.get_Rows().get_Item(i).get_Cells().get_Count());
            }

            while (_table.get_Rows().get_Item(i).get_Cells().get_Count() >
                get_Columns()) {
                _table.get_Rows().get_Item(i).get_Cells().RemoveAt(
                    _table.get_Rows().get_Item(i).get_Cells().get_Count() - 1);
            }
        }
    }

    protected void CreateChildControls()
    {
        /*
            Function name: CreateChildControls.
            Adds the Table and the text control to the control collection.
        */
        LiteralControl text;
        // Initializes the text control using the Title property.
        text = new LiteralControl("<h5>" + get_Title() + "</h5>");
        get_Controls().Add(text);

        _table = new Table();
        _table.set_BorderWidth(new Unit(2));
        get_Controls().Add(_table);
    }
}

The following code example uses the previous custom control. In particular, it builds a table whose attributes and content are defined at run time. Notice that the values shown in the @ Register directive reflect the previous command line.

<%@ Page Language="VB" %>
<%@ Register TagPrefix="AspNetSamples" Assembly="vb_mycontrolbuilder" Namespace="CustomControls" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>ControlBuilder Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
       <AspNetSamples:MyVB_CustomControl id="Custom1" 
                                         title="Auto-Generated Table"
                                         columns="3"
                                         rows="3"  
                                         runat="server">
         <mycell cellid="r0c0" BackColor="red" text="red cell"></mycell>
         <mycell cellid="r2c2" BackColor="green" text="green cell"></mycell>
       </AspNetSamples:MyVB_CustomControl>
    </div>
    </form>
</body>
</html>

<%@ Page Language="VJ#" %>
<%@ Register TagPrefix="AspNetSamples" Assembly="js_mycontrolbuilder" Namespace="CustomControls" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>ControlBuilder Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
       <AspNetSamples:MyJSL_CustomControl id="Custom1" 
                                         title="Auto-Generated Table"
                                         columns="3"
                                         rows="3"  
                                         runat="server">
         <mycell cellid="r0c0" BackColor="red" text="red cell"></mycell>
         <mycell cellid="r2c2" BackColor="green" text="green cell"></mycell>
       </AspNetSamples:MyJSL_CustomControl>
    </div>
    </form>
</body>
</html>

System.Object
  System.Web.UI.ControlBuilder
     Derived Classes

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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