Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/UI/WebControls/HiddenField.cs

@@ -0,0 +1,202 @@
+//------------------------------------------------------------------------------
+// <copyright file="HiddenField.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+
+namespace System.Web.UI.WebControls {
+
+    using System.ComponentModel;
+    using System.Collections.Specialized;
+
+
+    /// <devdoc>
+    /// Inserts a hidden field into the web form.
+    /// </devdoc>
+    [
+    ControlValueProperty("Value"),
+    DefaultEvent("ValueChanged"),
+    DefaultProperty("Value"),
+    Designer("System.Web.UI.Design.WebControls.HiddenFieldDesigner, " + AssemblyRef.SystemDesign),
+    ParseChildren(true),
+    PersistChildren(false),
+    NonVisualControl(),
+    SupportsEventValidation,
+    ]
+    public class HiddenField : Control, IPostBackDataHandler {
+
+        private static readonly object EventValueChanged = new object();
+
+        [
+        DefaultValue(false),
+        EditorBrowsable(EditorBrowsableState.Never),
+        ]
+        public override bool EnableTheming {
+            get {
+                return false;
+            }
+            set {
+                throw new NotSupportedException(SR.GetString(SR.NoThemingSupport, this.GetType().Name));
+            }
+        }
+
+        [
+        DefaultValue(""),
+        EditorBrowsable(EditorBrowsableState.Never),
+        ]
+        public override string SkinID {
+            get {
+                return String.Empty;
+            }
+            set {
+                throw new NotSupportedException(SR.GetString(SR.NoThemingSupport, this.GetType().Name));
+            }
+        }
+
+
+        /// <devdoc>
+        /// Gets or sets the value of the hidden field.
+        /// </devdoc>
+        [
+        Bindable(true),
+        WebCategory("Behavior"),
+        DefaultValue(""),
+        WebSysDescription(SR.HiddenField_Value)
+        ]
+        public virtual string Value {
+            get {
+                string s = (string)ViewState["Value"];
+                return (s != null) ? s : String.Empty;
+            }
+            set {
+                ViewState["Value"] = value;
+            }
+        }
+
+
+        /// <devdoc>
+        /// Raised when the value of the hidden field is changed on the client.
+        /// </devdoc>
+        [
+        WebCategory("Action"),
+        WebSysDescription(SR.HiddenField_OnValueChanged)
+        ]
+        public event EventHandler ValueChanged {
+            add {
+                Events.AddHandler(EventValueChanged, value);
+            }
+            remove {
+                Events.RemoveHandler(EventValueChanged, value);
+            }
+        }
+
+
+        protected override ControlCollection CreateControlCollection() {
+            return new EmptyControlCollection(this);
+        }
+
+        [
+        EditorBrowsable(EditorBrowsableState.Never),
+        ]
+        public override void Focus() {
+            throw new NotSupportedException(SR.GetString(SR.NoFocusSupport, this.GetType().Name));
+        }
+
+
+        protected virtual bool LoadPostData(string postDataKey, NameValueCollection postCollection) {
+            ValidateEvent(UniqueID);
+
+            string current = Value;
+            string postData = postCollection[postDataKey];
+            if (!current.Equals(postData, StringComparison.Ordinal)) {
+                Value = postData;
+                return true;
+            }
+            return false;
+        }
+
+
+        protected internal override void OnPreRender(EventArgs e) {
+            base.OnPreRender(e);
+            if (SaveValueViewState == false) {
+                ViewState.SetItemDirty("Value", false);
+            }
+        }
+
+
+        protected virtual void OnValueChanged(EventArgs e) {
+            EventHandler handler = (EventHandler)Events[EventValueChanged];
+            if (handler != null) {
+                handler(this, e);
+            }
+        }
+
+
+        protected virtual void RaisePostDataChangedEvent() {
+            OnValueChanged(EventArgs.Empty);
+        }
+
+
+        protected internal override void Render(HtmlTextWriter writer) {
+            string uniqueID = UniqueID;
+
+            // Make sure we are in a form tag with runat=server.
+            if (Page != null) {
+                Page.VerifyRenderingInServerForm(this);
+                Page.ClientScript.RegisterForEventValidation(uniqueID);
+            }
+
+            writer.AddAttribute(HtmlTextWriterAttribute.Type, "hidden");
+
+            if (uniqueID != null) {
+                writer.AddAttribute(HtmlTextWriterAttribute.Name, uniqueID);
+            }
+
+            if (ID != null) {
+                writer.AddAttribute(HtmlTextWriterAttribute.Id, ClientID);
+            }
+
+            string s;
+            s = Value;
+            if (s.Length > 0) {
+                writer.AddAttribute(HtmlTextWriterAttribute.Value, s);
+            }
+
+            writer.RenderBeginTag(HtmlTextWriterTag.Input);
+            writer.RenderEndTag();
+        }
+
+        /// <devdoc>
+        ///    Determines whether the Value must be stored in view state, to
+        ///    optimize the size of the saved state.
+        /// </devdoc>
+        private bool SaveValueViewState {
+            get {
+                // Must be saved when
+                // 1. There is a registered event handler for EventValueChanged
+                // 2. Control is not visible, because the browser's post data will not include this control
+                // 3. The instance is a derived instance, which might be overriding the OnValueChanged method
+
+                if ((Events[EventValueChanged] != null) ||
+                    (Visible == false) ||
+                    (this.GetType() != typeof(HiddenField))) {
+                    return true;
+                }
+
+                return false;
+            }
+        }
+
+        #region Implementation of IPostBackDataHandler
+
+        bool IPostBackDataHandler.LoadPostData(string postDataKey, NameValueCollection postCollection) {
+            return LoadPostData(postDataKey, postCollection);
+        }
+
+
+        void IPostBackDataHandler.RaisePostDataChangedEvent() {
+            RaisePostDataChangedEvent();
+        }
+        #endregion
+    }
+}