combobox.cs

ASP C#代码实例 适合初学人士学习使用

		protected internal virtual string ClientFormID {
			get {
				Control parent = this;

				while (parent != null) {
					if (parent is System.Web.UI.HtmlControls.HtmlForm)
						break;

					parent = parent.Parent;
				}
				return parent.ClientID;
			}
		}
		#endregion

		#region Render Methods
		/// <summary>
		/// This member overrides Control.AddParsedSubObject.
		/// </summary>
		/// <param name="obj"></param>
		protected override void AddParsedSubObject(object obj) {
			if (obj is ListItem) {
				this.Items.Add((ListItem) obj);
				return;
			}
			throw new HttpException("ComboBox Cannot Have Children Of Type " + obj.GetType().Name);
		}
		/// <summary>
		/// This member overrides Control.Render.
		/// </summary>
		/// <param name="writer"></param>
		protected override void Render(HtmlTextWriter writer) {
			this.RenderBeginTag(writer);
			this.RenderChildren(writer);
			this.RenderEndTag(writer);
		}

		/// <summary>
		/// This member supports the .NET Framework infrastructure and is not intended to be used directly from your code.
		/// </summary>
		/// <param name="writer"></param>
		public override void RenderBeginTag(HtmlTextWriter writer) {
			writer.Write("<?XML:NAMESPACE PREFIX=\"" + TagNamespace
				+ "\" />\n<?IMPORT NAMESPACE=\"" + TagNamespace + "\" IMPLEMENTATION=\""
				+ this.GetFilePath() + "combobox.htc" + "\" />");
			writer.WriteLine();
			writer.WriteBeginTag(TagNamespace + ":" + ComboBoxTagName);
			this.RenderAttributes(writer);
			writer.Write(">");
		} 

		/// <summary>
		/// This member overrides Control.RenderChildren.
		/// </summary>
		/// <param name="writer"></param>
		protected override void RenderChildren(HtmlTextWriter writer) {
			ListItem item;
			writer.WriteLine();
			writer.Indent = writer.Indent + 1;
			if (this.Items.Count > 0) {
				for (int i=0; i < this.Items.Count; i++) {
					item = this.Items[i];
					writer.WriteBeginTag("option");
					if (item.Selected) {
						writer.WriteAttribute("selected", "true");
					}
					writer.WriteAttribute("value", item.Value, true);
					item.Attributes.Render(writer);
					writer.Write('>');
					HttpUtility.HtmlEncode(item.Text, writer);
					writer.WriteEndTag("option");
					writer.WriteLine();
				} 
			}
			writer.Indent = writer.Indent - 1;
		}

		/// <summary>
		/// This member supports the .NET Framework infrastructure and is not intended to be used directly from your code.
		/// </summary>
		/// <param name="writer"></param>
		protected virtual void RenderAttributes(HtmlTextWriter writer) {
			if (base.ID != null) {
				writer.WriteAttribute("id", base.ClientID);
				writer.WriteAttribute("name", this.UniqueID);
			}
			if (!this.Enabled)
				writer.WriteAttribute("Enabled","false");
			if (this.AutoValidate)
				writer.WriteAttribute("AutoValidate","true");
			writer.WriteAttribute("ParentFormID", this.ClientFormID);
			writer.WriteAttribute("ResourcesDirectory",this.GetFilePath());
			if (this.AutoPostBack) {
				string sOnChangeCmd = this.Attributes["onchange"];
				if (sOnChangeCmd != null) {
					this.Attributes["onchange"] = (sOnChangeCmd.EndsWith(";")) ? sOnChangeCmd + Page.GetPostBackEventReference(this, String.Empty)+ ";" : sOnChangeCmd + ";" + Page.GetPostBackEventReference(this, String.Empty);
				} else {
					this.Attributes.Add("onchange", Page.GetPostBackEventReference(this, String.Empty));
				}
			}
			this.Attributes.Render(writer);
		} 

		/// <summary>
		/// This member supports the .NET Framework infrastructure and is not intended to be used directly from your code.
		/// </summary>
		/// <param name="writer"></param>
		public override void RenderEndTag(HtmlTextWriter writer) {
			writer.WriteEndTag(TagNamespace + ":" + ComboBoxTagName);
		}
		#endregion

		/// <summary>
		/// Overridden. Creates an EmptyControlCollection to prevent controls from
		/// being added to the ControlCollection.
		/// </summary>
		/// <returns>An EmptyControlCollection object.</returns>
		protected override ControlCollection CreateControlCollection() {
			return new EmptyControlCollection(this);
		}

		
		/// <summary>
		/// This member supports the .NET Framework infrastructure and is not intended to be used directly from your code.
		/// </summary>
		protected virtual void ClearSelection() {
			foreach (ListItem item in this.Items) {
				item.Selected = false;
			}
		}

		/// <summary>
		/// This member supports the .NET Framework infrastructure and is not intended to be used directly from your code.
		/// </summary>
		/// <param name="index"></param>
		protected virtual void Select(int index) {
			if (index < -1 || index >= this.Items.Count)
				throw new ArgumentOutOfRangeException("index");
			else {
				this.ClearSelection();
				this.Items[index].Selected = true;
			}
		}


		#region PostBack Methods
		public virtual void RaisePostDataChangedEvent() {
			this.OnServerChange(EventArgs.Empty);
		}
		public virtual bool LoadPostData(string postDataKey, NameValueCollection postCollection) {
			string sValue = this.Value;
			string sPostedValue = postCollection.GetValues(postDataKey)[0];
			if (sPostedValue != null && !sValue.Equals(sPostedValue)) {
				this.Value = sPostedValue;
				return true; 
			}
			return false;
		}
		protected override void LoadViewState(object savedState) {
			if (savedState != null) {
				object[] State = (object[])savedState;
				this.Value = (string) State[0];
				ArrayList ItemsList = (ArrayList) State[1];
				foreach (object obj in ItemsList) {
					Triplet trip = (Triplet) obj;
					if (this.Items.FindByValue((string)trip.First)==null) {
						ListItem item = new ListItem();
						item.Value = (string) trip.First;
						item.Text = (string) trip.Second;
						item.Selected = (bool) trip.Third;
						this.Items.Add(item);
					}
				}
			}
		}
		protected override object SaveViewState() {
			ArrayList ItemsList = new ArrayList();
			foreach (ListItem item in this.Items) {
				ItemsList.Add(new Triplet(item.Value, item.Text, item.Selected));
			}
			object[] savedState = new object[2];
			savedState[0] = this.Value;
			savedState[1] = ItemsList;
			return savedState;
		}
		#endregion

		/// <summary>
		/// This member overrides Control.OnPreRender
		/// </summary>
		/// <param name="e"></param>
		protected override void OnPreRender(EventArgs e) {
			if (base.Page != null) {
				base.Page.RegisterRequiresPostBack(this);
			}
		} 

		/// <summary>
		/// Raises the ServerChange event of the ComboBox control. This allows you to provide a custom handler for the event.
		/// </summary>
		/// <param name="e">A System.EventArgs that contains the event data.</param>
		protected virtual void OnServerChange(EventArgs e) {
			EventHandler handler = (EventHandler) this.Events[this.EventServerChange];
			if (handler != null)
				handler.Invoke(this, e);
		}

		/// <summary>
		/// This member overrides Control.OnDataBinding.
		/// </summary>
		/// <param name="e">A System.EventArgs that contains the event data.</param>
		protected override void OnDataBinding(EventArgs e) {
			base.OnDataBinding(e);
			IEnumerable eDataSource = GetResolvedDataSource();
			if (eDataSource != null) {
				this.Items.Clear();
				if (eDataSource is ICollection) {
					this.Items.Capacity = ((ICollection)eDataSource).Count;
				}
				try {
					for(IEnumerator ie = eDataSource.GetEnumerator() ; ie.MoveNext();) {					
						ListItem item = new ListItem();
						item.Text = (this.DataTextField.Length > 0)?DataBinder.GetPropertyValue(ie.Current, this.DataTextField, null):ie.Current.ToString();
						item.Value = (this.DataValueField.Length > 0)?DataBinder.GetPropertyValue(ie.Current, this.DataValueField, null):ie.Current.ToString();
						this.Items.Add(item);
					}
				} 
				catch {}
			}
			if (this.cachedSelectedIndex != -1) {
				this.SelectedIndex = this.cachedSelectedIndex;
				this.cachedSelectedIndex = -1;
			}
		}

		#region Private Methods
		private IEnumerable GetResolvedDataSource() {
			if (this.DataSource == null) {
				return null; 
			}
			if (this.DataSource is IListSource) {
				IListSource iListSource = (IListSource)this.DataSource;
				IList iList = iListSource.GetList();
				if (!iListSource.ContainsListCollection) {
					return iList; 
				}
				if (iList != null && iList is ITypedList) {
					ITypedList iTypeList = ((ITypedList) iList);
					PropertyDescriptorCollection collection = iTypeList.GetItemProperties(new PropertyDescriptor[0]);
					if ((collection != null) && (collection.Count != 0)) {
						PropertyDescriptor discriptor = null;
						if ((this.DataMember == null) || (this.DataMember.Length == 0)) {
							discriptor = collection[0];
						}
						else {
							discriptor = collection.Find(this.DataMember, true);
						}
						if (discriptor != null) {
							object key = iList[0];
							object val = discriptor.GetValue(key);
							if ((val != null) && val is IEnumerable) {
								return ((IEnumerable) val); 
							}
						}
						throw new HttpException("The datasource does not contain a member named " + this.DataMember);
					}
					throw new HttpException("Datasource does not contain any members.");
				}
			}
			if (this.DataSource is IEnumerable) {
				return ((IEnumerable) this.DataSource);
			}
			return null;
		}
		private string GetFilePath() {
			// Look at the current configuration for the path
			
			string sFilePath = ConfigurationSettings.AppSettings["PROGWEBCONTORLS_COMMONFILEPATH"];
			if (sFilePath != null) {
				if (sFilePath.Length > 0) {
					if (sFilePath[sFilePath.Length - 1] != '/') {
						sFilePath += "/";
					}
				}
				return sFilePath;
			}

			// Return the default path with version number
			System.Reflection.Assembly assembly = typeof(ComboBox).Assembly;
			Version version = assembly.GetName().Version;

			return DefaultCommonFilesRoot + version.Major.ToString() + "_" + version.Minor.ToString() + "/";
		}

		#endregion
	}
}