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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)

public class 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
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Collections;
using System.Drawing;
using System.Security.Permissions;

namespace CustomControls
{
	[AspNetHostingPermission(SecurityAction.Demand,
		Level = AspNetHostingPermissionLevel.Minimal)]
	public class MyTableCell : TableCell, INamingContainer { };

	[AspNetHostingPermission(SecurityAction.Demand,
		Level = AspNetHostingPermissionLevel.Minimal)]
	public class MyCell
	/*
	 * Class name: MyCell.
	 * Declares the class for the child controls to include in the control collection.
	 */
	{
		string _id;
		string _value;
		Color _backColor;

		public string CellID
		{
			get
			{ return _id; }
			set
			{ _id = value; }
		}

		public string Text
		{
			get
			{ return _value; }
			set
			{ _value = value; }
		}

		public Color BackColor
		{
			get
			{ return _backColor; }
			set
			{ _backColor = value; }
		}
	};

	[AspNetHostingPermission(SecurityAction.Demand,
	Level = AspNetHostingPermissionLevel.Minimal)]
	public class MyControlBuilder : ControlBuilder
	{

		public override 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 typeof(MyCell);
			return null;
		}

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

	}
	[AspNetHostingPermission(SecurityAction.Demand,
		Level = AspNetHostingPermissionLevel.Minimal)]
	[ControlBuilderAttribute(typeof(MyControlBuilder))]
	public class MyCS_CustomControl : Control, INamingContainer
	/*
	 * Class name: MyCS_CustomControl.
	 * Processes the element declarations within a control declaration. 
	 * This builds the actual control.
	 */
	{
		// Declares the custom control that must be built programmatically.
		Table _table;

		private String _title;
		private int _rows;
		private int _columns;

		Hashtable _cellObjects = new Hashtable();

		// Rows property to be used as the attribute name in the Web page.  
		public int Rows
		{
			get
			{ return _rows; }
			set
			{ _rows = value; }
		}

		// Columns property to be used as the attribute name in the Web page.
		public int Columns
		{
			get
			{ return _columns; }
			set
			{ _columns = value; }
		}

		// Title property to be used as the attribute name in the Web page.
		public string Title
		{
			get
			{ return _title; }
			set
			{ _title = value; }
		}

		protected void createNewRow(int rowNumber)
		{

			// Creates a row and adds it to the table.
			TableRow row;

			row = new TableRow();
			_table.Rows.Add(row);

			// Creates a cell that contains text.

			for (int y = 0; y < Columns; y++)
				appendCell(row, rowNumber, y);

		}

		protected void appendCell(TableRow row, int rowNumber, int cellNumber)
		{
			TableCell cell;
			TextBox 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 (_cellObjects[textbox.ID] != null)
			{
				MyCell cellLookup;
				cellLookup = (MyCell)_cellObjects[textbox.ID];

				textbox.Text = cellLookup.Text;
				textbox.BackColor = cellLookup.BackColor;
			}
			else
				textbox.Text = "Row: " + rowNumber.ToString() + " Cell: " +
				cellNumber.ToString();

			row.Cells.Add(cell);

		}

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

		}

		protected override 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.Rows.Count < Rows)
			{
				createNewRow(_table.Rows.Count);
			}

			// Checks that each row has the correct number of columns.
			for (int i = 0; i < _table.Rows.Count; i++)
			{
				while (_table.Rows[i].Cells.Count < Columns)
				{
					appendCell(_table.Rows[i], i, _table.Rows[i].Cells.Count);
				}

				while (_table.Rows[i].Cells.Count > Columns)
				{
					_table.Rows[i].Cells.RemoveAt(_table.Rows[i].Cells.Count - 1);
				}
			}
		}

		protected override 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>" + Title + "</h5>");
			Controls.Add(text);

			_table = new Table();
			_table.BorderWidth = 2;
			Controls.Add(_table);
		}
	}
}

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="C#" %>
<%@ Register TagPrefix="AspNetSamples" Assembly="cs_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:MyCS_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:MyCS_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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