Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

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

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+//------------------------------------------------------------------------------
+// <copyright file="ReadOnlyHierarchicalDataSource.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+
+namespace System.Web.UI.WebControls {
+
+    using System;
+    using System.Collections;
+    using System.ComponentModel;
+    using System.Web;
+    using System.Web.UI;
+    using System.Web.Util;
+
+
+    /// <devdoc>
+    /// Helper class for hierarchical data bound controls to wrap an generic
+    /// data source with a strongly typed IHierarchicalDataSource. This class
+    /// automatically handles other IHierarchicalDataSources and
+    /// IHierarchicalEnumerables. This class uses
+    /// ReadOnlyHierarchicalDataSourceView to represent individual views.
+    /// </devdoc>
+    internal sealed class ReadOnlyHierarchicalDataSource : IHierarchicalDataSource {
+
+        private object _dataSource;
+
+        public ReadOnlyHierarchicalDataSource(object dataSource) {
+            Debug.Assert(dataSource == null || (dataSource is IHierarchicalEnumerable || dataSource is IHierarchicalDataSource), "Expected dataSource to be either null, an IHierarchicalEnumerable, or an IHierarchicalDataSource.");
+            _dataSource = dataSource;
+        }
+
+        #region Implementation of IHierarchicalDataSource
+        event EventHandler IHierarchicalDataSource.DataSourceChanged {
+            add {
+            }
+            remove {
+            }
+        }
+
+        /// <devdoc>
+        /// Check for IHierarchicalDataSource and IHierarchicalEnumerable, and
+        /// return an approprite HierarchicalDataSourceView.
+        /// </devdoc>
+        HierarchicalDataSourceView IHierarchicalDataSource.GetHierarchicalView(string viewPath) {
+            // Check first for IHierarchicalDataSource
+            IHierarchicalDataSource ds = _dataSource as IHierarchicalDataSource;
+            if (ds != null) {
+                return ds.GetHierarchicalView(viewPath);
+            }
+
+            IHierarchicalEnumerable enumerable = _dataSource as IHierarchicalEnumerable;
+            if (enumerable != null && viewPath != null && viewPath.Length != 0) {
+                throw new InvalidOperationException(SR.GetString(SR.ReadOnlyHierarchicalDataSourceView_CantAccessPathInEnumerable));
+            }
+            return new ReadOnlyHierarchicalDataSourceView(enumerable);
+        }
+        #endregion
+    }
+}
+