Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

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

@@ -0,0 +1,110 @@
+namespace System.Web.UI.WebControls {
+    /// <summary>
+    /// This class tracks the values of SelectMethod parameters of ModelDataSourceView that use a custom value provider across multiple page requests.
+    /// </summary>
+    internal sealed class MethodParameterValue : IStateManager {
+
+        private MethodParametersDictionary _owner;
+        private bool _tracking;
+        private StateBag _viewState;
+        private static readonly string s_valueViewStateKey = "ParameterValue";
+
+        /// <devdoc>
+        /// Tells the Parameter the dictionary it belongs to
+        /// </devdoc>
+        internal void SetOwner(MethodParametersDictionary owner) {
+            _owner = owner;
+        }
+
+        /// <devdoc>
+        /// Raises the ParameterChanged event.
+        /// </devdoc>
+        private void OnParameterChanged() {
+            if (_owner != null) {
+                _owner.CallOnParametersChanged();
+            }
+        }
+
+        internal void UpdateValue(object newValue) {
+            object oldValue = ViewState[s_valueViewStateKey];
+            ViewState[s_valueViewStateKey] = newValue;
+
+            if ((newValue == null && oldValue != null) || (newValue != null && !newValue.Equals(oldValue))) {
+                OnParameterChanged();
+            }
+        }
+
+        /// <devdoc>
+        /// Indicates whether the MethodParameter is tracking view state.
+        /// </devdoc>
+        private bool IsTrackingViewState {
+            get {
+                return _tracking;
+            }
+        }
+
+        /// <devdoc>
+        /// Indicates a dictionary of state information that allows you to save and restore
+        /// the state of a MethodParameter across multiple requests for the same page.
+        /// </devdoc>
+        private StateBag ViewState {
+            get {
+                if (_viewState == null) {
+                    _viewState = new StateBag();
+                    if (_tracking)
+                        _viewState.TrackViewState();
+                }
+
+                return _viewState;
+            }
+        }
+
+        /// <devdoc>
+        /// Loads view state.
+        /// </devdoc>
+        private void LoadViewState(object savedState) {
+            if (savedState != null) {
+                ViewState.LoadViewState(savedState);
+            }
+        }
+
+        /// <devdoc>
+        /// Saves view state.
+        /// </devdoc>
+        private object SaveViewState() {
+            return (_viewState != null) ? _viewState.SaveViewState() : null;
+        }
+
+        /// <devdoc>
+        /// Tells the MethodParameter to start tracking property changes.
+        /// </devdoc>
+        private void TrackViewState() {
+            _tracking = true;
+
+            if (_viewState != null) {
+                _viewState.TrackViewState();
+            }
+        }
+
+        #region Implementation of IStateManager
+
+        bool IStateManager.IsTrackingViewState {
+            get {
+                return IsTrackingViewState;
+            }
+        }
+
+        void IStateManager.LoadViewState(object savedState) {
+            LoadViewState(savedState);
+        }
+
+        object IStateManager.SaveViewState() {
+            return SaveViewState();
+        }
+
+        void IStateManager.TrackViewState() {
+            TrackViewState();
+        }
+        #endregion
+    }
+}