handle add column request (#1272)

* handle add column request

* comments

* rename data to ViewModel

src/Microsoft.SqlTools.ServiceLayer/TableDesigner/Contracts/ViewModel/TableViewModel.cs

@@ -0,0 +1,37 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Newtonsoft.Json;
+
+namespace Microsoft.SqlTools.ServiceLayer.TableDesigner.Contracts
+{
+    /// <summary>
+    /// The view model for a table object
+    /// </summary>
+    public class TableViewModel : ObjectViewModelBase
+    {
+        public DropdownProperties Schema { get; set; } = new DropdownProperties();
+
+        public InputBoxProperties Description { get; set; } = new InputBoxProperties();
+
+        public TableColumnCollection Columns { get; set; } = new TableColumnCollection();
+
+        public InputBoxProperties Script { get; set; } = new InputBoxProperties();
+    }
+
+    public class TableColumnCollection : TableComponentProperties<TableColumnViewModel>
+    {
+        [JsonIgnore]
+        protected override string NewObjectNamePrefix { get { return "column"; } }
+
+        protected override TableColumnViewModel CreateNew(string name)
+        {
+            //TODO: Add the default values
+            var column = new TableColumnViewModel();
+            column.Name.Value = this.GetDefaultNewObjectName();
+            return column;
+        }
+    }
+}