HtmlHead.cs source code in C# .NET

                        
Code:
                         / 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / xsp / System / Web / UI / HtmlControls / HtmlHead.cs / 1305376 / HtmlHead.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Web.UI.HtmlControls { 
    using System; 
    using System.Collections;
    using System.Collections.Specialized; 
    using System.ComponentModel;
    using System.Globalization;
    using System.Web;
    using System.Web.UI; 
    using System.Web.UI.WebControls;
    using System.Security.Permissions; 
 
    public class HtmlHeadBuilder : ControlBuilder {
 

        public override Type GetChildControlType(string tagName, IDictionary attribs) {
            if (String.Equals(tagName, "title", StringComparison.OrdinalIgnoreCase))
                return typeof(HtmlTitle); 

            if (String.Equals(tagName, "link", StringComparison.OrdinalIgnoreCase)) 
                return typeof(HtmlLink); 

            if (String.Equals(tagName, "meta", StringComparison.OrdinalIgnoreCase)) 
                return typeof(HtmlMeta);

            return null;
        } 

 
        public override bool AllowWhitespaceLiterals() { 
            return false;
        } 
    }

    /// 
    /// Represents the HEAD element. 
    /// 
    [ 
    ControlBuilderAttribute(typeof(HtmlHeadBuilder)) 
    ]
    public sealed class HtmlHead : HtmlGenericControl { 

        private StyleSheetInternal _styleSheet;
        private HtmlTitle _title;
        private String _cachedTitleText; 
        private HtmlMeta _description;
        private String _cachedDescription; 
        private HtmlMeta _keywords; 
        private String _cachedKeywords;
 
        /// 
        /// Initializes an instance of an HtmlHead class.
        /// 
        public HtmlHead() : base("head") { 
        }
 
        public HtmlHead(string tag) : base(tag) { 
            if (tag == null) {
                tag = String.Empty; 
            }
            _tagName = tag;
        }
 
        public IStyleSheet StyleSheet {
            get { 
                if (_styleSheet == null) { 
                    _styleSheet = new StyleSheetInternal(this);
                } 

                return _styleSheet;
            }
        } 

        public String Title { 
            get { 
                if (_title == null) {
                    return _cachedTitleText; 
                }

                return _title.Text;
            } 
            set {
                if (_title == null) { 
                    // Side effect of adding a title to the control assigns _title 
                    _cachedTitleText = value;
                } 
                else {
                    _title.Text = value;
                }
            } 
        }
 
        public String Description { 
            get {
                if (_description == null) { 
                    return _cachedDescription;
                }

                return _description.Content; 
            }
            set { 
                if (_description == null) { 
                    // Side effect of adding a description to the control assigns _description
                    _cachedDescription = value; 
                }
                else {
                    _description.Content = value;
                } 
            }
        } 
 
        public String Keywords {
            get { 
                if (_keywords == null) {
                    return _cachedKeywords;
                }
 
                return _keywords.Content;
            } 
            set { 
                if (_keywords == null) {
                    // Side effect of adding a title to the control assigns _title 
                    _cachedKeywords = value;
                }
                else {
                    _keywords.Content = value; 
                }
            } 
        } 

        protected internal override void AddedControl(Control control, int index) { 
            base.AddedControl(control, index);

            if (control is HtmlTitle) {
                if (_title != null) { 
                    throw new HttpException(SR.GetString(SR.HtmlHead_OnlyOneTitleAllowed));
                } 
 
                _title = (HtmlTitle)control;
            } 
            else if (control is HtmlMeta) {
                // We will only use the first matching meta tag per, and ignore any others
                HtmlMeta meta = (HtmlMeta)control;
                if (_description == null && string.Equals(meta.Name, "description", StringComparison.OrdinalIgnoreCase)) { 
                    _description = meta;
                } 
                else if (_keywords == null && string.Equals(meta.Name, "keywords", StringComparison.OrdinalIgnoreCase)) { 
                    _keywords = meta;
                } 
            }
        }

        ///  
        /// 
        /// Allows the HEAD element to register itself with the page. 
        ///  
        protected internal override void OnInit(EventArgs e) {
            base.OnInit(e); 

            Page p = Page;
            if (p == null) {
                throw new HttpException(SR.GetString(SR.Head_Needs_Page)); 
            }
            if (p.Header != null) { 
                throw new HttpException(SR.GetString(SR.HtmlHead_OnlyOneHeadAllowed)); 
            }
            p.SetHeader(this); 
        }

        internal void RegisterCssStyleString(string outputString) {
            ((StyleSheetInternal)StyleSheet).CSSStyleString = outputString; 
        }
 
        protected internal override void RemovedControl(Control control) { 
            base.RemovedControl(control);
 
            if (control is HtmlTitle) {
                _title = null;
            }
            // There can be many meta tags, so we only clear it if its the correct meta 
            else if (control == _description) {
                _description = null; 
            } 
            else if (control == _keywords) {
                _keywords = null; 
            }
        }

        ///  
        /// 
        /// Notifies the Page when the HEAD is being rendered. 
        ///  
        protected internal override void RenderChildren(HtmlTextWriter writer) {
            base.RenderChildren(writer); 

            if (_title == null) {
                // Always render out a