Object Explorer Service (#311)

* moving OE service from an old branch

src/Microsoft.SqlTools.ServiceLayer/ObjectExplorer/SmoModel/SmoQueryContext.cs

@@ -0,0 +1,102 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Globalization;
+using Microsoft.SqlServer.Management.Smo;
+using Microsoft.SqlTools.Extensibility;
+using Microsoft.SqlTools.ServiceLayer.ObjectExplorer.Nodes;
+
+namespace Microsoft.SqlTools.ServiceLayer.ObjectExplorer.SmoModel
+{
+    /// <summary>
+    /// Context object containing key properties needed to query for SMO objects
+    /// </summary>
+    public class SmoQueryContext
+    {
+        /// <summary>
+        /// Creates a context object with a server to use as the basis for any queries
+        /// </summary>
+        /// <param name="server"></param>
+        public SmoQueryContext(Server server, IMultiServiceProvider serviceProvider)
+        {
+            Server = server;
+            ServiceProvider = serviceProvider;
+        }
+
+        /// <summary>
+        /// The server SMO will query against
+        /// </summary>
+        public Server Server { get; private set; }
+
+        /// <summary>
+        /// Optional Database context object to query against
+        /// </summary>
+        public Database Database { get; set; }
+
+        /// <summary>
+        /// Parent of a give node to use for queries
+        /// </summary>
+        public SmoObjectBase Parent { get; set; }
+
+        /// <summary>
+        /// A query loader that can be used to find <see cref="SmoQuerier"/> objects
+        /// for specific SMO types
+        /// </summary>
+        public IMultiServiceProvider ServiceProvider { get; private set; }
+        
+        /// <summary>
+        /// Helper method to cast a parent to a specific type
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <returns></returns>
+        public T ParentAs<T>()
+            where T : TreeNode
+        {
+            return Parent as T;
+        }
+
+        /// <summary>
+        /// Gets the <see cref="ObjectExplorerService"/> if available, by looking it up
+        /// from the <see cref="ServiceProvider"/>
+        /// </summary>
+        /// <returns></returns>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if the <see cref="ServiceProvider"/> is not set or the <see cref="ObjectExplorerService"/>
+        /// isn't available from that provider
+        /// </exception>
+        public ObjectExplorerService GetObjectExplorerService()
+        {
+            if (ServiceProvider == null)
+            {
+                throw new InvalidOperationException(SqlTools.Hosting.Localization.sr.ServiceProviderNotSet);
+            }
+            ObjectExplorerService service = ServiceProvider.GetService<ObjectExplorerService>();
+            if (service == null)
+            {
+                throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, 
+                    SqlTools.Hosting.Localization.sr.ServiceNotFound, nameof(ObjectExplorerService)));
+            }
+
+            return service;
+        }
+        /// <summary>
+        /// Copies the context for use by another node
+        /// </summary>
+        /// <param name="parent">New Parent to set</param>
+        /// <returns>new <see cref="SmoQueryContext"/> with all fields except <see cref="Parent"/> the same</returns>
+        public SmoQueryContext CopyWithParent(SmoObjectBase parent)
+        {
+            SmoQueryContext context = new SmoQueryContext(this.Server, this.ServiceProvider)
+            {
+                Database = this.Database,
+                Parent = parent
+            };
+            return context;
+        }
+    }
+}