docs(mccb): update info on virtualization requirements

Author: marin-bratanov

controls/multicolumncombobox/data-binding/client-side.md

@@ -44,7 +44,7 @@ The widget only shows data and so only the **Select** settings and `ServiceType`
 
 To bind to a RadClientDataSource instance, set the `ClientDataSourceID` property to the ID of the client data source control.
 
-RadClientDataSource is a wrapper over the Kendo UI DataSource as well. It is a separate control tag that provides some more features (like settings for server filtering or server paging). If you want to use [virtualization]({%slug multicolumncombobox/functionality/virtualization%}), you must use a RadClientDataSource. For all other cases, the built-in `WebServiceSettings` will serve the same purpose.
+RadClientDataSource is a wrapper over the Kendo UI DataSource as well. It is a separate control tag that provides some more features pertainig to CRUD operations that are not relevant to the multi-column combo box.
 
 >caption Example 2: Binding to a RadClientDataSource
 

controls/multicolumncombobox/functionality/virtualization.md

@@ -19,25 +19,86 @@ Virtualization requires:
 * `Height` and `VirtualSettings.ItemHeight` to be set in pixel values.
 * All columns to have `Width` set in pixels.
 * Remote data binding.
-* That the corresponding service provides the paging of the data. This means that a `RadClientDataSource` can be used for virtualization and it requires the following properties:
+* That the corresponding service provides the paging of the data. This means that the following properties must be set:
     * `PageSize` set according to the `Height` and `ItemHeight` (usually `((Height / ItemHeight) * 4)`)
     * `EnableServerFiltering="true"`
     * `AllowPaging="true"`
     * `EnableServerPaging="true"`
 
 >important RadMultiColumnComboBox is a server-side wrapper over the Kendo UI MultiColumnComboBox widget. The [Virtualization in Kendo DropDowns](https://docs.telerik.com/kendo-ui/controls/editors/combobox/virtualization) article explains in detail how virtualization works in the underlying widgets, and lists its behaviors, specifics and requirements. You should get familiar with it before using virtualization in RadMultiColumnComboBox.
 
-## Example
+## Examples
 
-The following example shows how you can use virtualization with the service from the [Kendo Service repo](https://github.com/telerik/kendo-ui-demos-service). It also includes a [sample value mapper](https://github.com/telerik/kendo-ui-demos-service/blob/master/demos-and-odata-v3/KendoCRUDService/Controllers/OrdersController.cs) function that is optional.
+The following examples show how you can use virtualization with the service from the [Kendo Service repo](https://github.com/telerik/kendo-ui-demos-service). It also includes a [sample value mapper](https://github.com/telerik/kendo-ui-demos-service/blob/master/demos-and-odata-v3/KendoCRUDService/Controllers/OrdersController.cs) function that is optional.
 
->caption Example 1: Virtualization in RadMultiColumnComboBox with RadClientDataSource plus a sample value mapper function.
+>caption Example 1: Virtualization in RadMultiColumnComboBox. Includes a sample value mapper function
+
+````ASP.NET
+<telerik:RadMultiColumnComboBox runat="server" ID="RadMultiColumnComboBox1" Skin="Default"
+
+    EnableServerFiltering="true"
+    AllowPaging="true"
+    EnableServerPaging="true"
+    PageSize="80"
+    
+    
+    Height="400" Width="300px"
+    Placeholder="select from the dropdown or type"
+    DataTextField="ShipName" DataValueField="OrderID"
+    Filter="Contains" FilterFields="ShipName,ShipCountry">
+    
+    <WebServiceSettings ServiceType="OData" Select-DataType="JSON">
+        <Select Url="https://demos.telerik.com/kendo-ui/service/Northwind.svc/Orders" />
+    </WebServiceSettings>
+    <VirtualSettings ItemHeight="28" ValueMapper="valueMapper" />
+    
+    <ColumnsCollection>
+        <telerik:MultiColumnComboBoxColumn Field="OrderID" Title="Order" Width="100" />
+        <telerik:MultiColumnComboBoxColumn Field="ShipName" Title="Ship" Width="300" />
+        <telerik:MultiColumnComboBoxColumn Field="ShipCountry" Title="Country " Width="200" />
+    </ColumnsCollection>
+</telerik:RadMultiColumnComboBox>
+
+<script>
+    function valueMapper(options) {
+        $telerik.$.ajax({
+            url: "https://demos.telerik.com/kendo-ui/service/Orders/ValueMapper",
+            type: "GET",
+            dataType: "jsonp",
+            data: convertValues(options.value),
+            success: function (data) {
+                options.success(data);
+            }
+        })
+    }
+     
+    function convertValues(value) {
+        var data = {};
+        value = $telerik.$.isArray(value) ? value : [value];
+     
+        for (var idx = 0; idx < value.length; idx++) {
+            data["values[" + idx + "]"] = value[idx];
+        }
+     
+        return data;
+    }
+</script>
+````
+
+You can achieve the same through a RadClientDataSource control. In such a case, you must set the web service settings (including the page size, and enabling the server operations) on the data source control instead of for the multi column combo box.
+
+>caption Example 2: Virtualization in RadMultiColumnComboBox with RadClientDataSource plus a sample value mapper function.
 
 ````ASP.NET
 <telerik:RadMultiColumnComboBox runat="server" ID="RadMultiColumnComboBox1" Filter="Contains" Skin="Default"
-    ClientDataSourceID="RadClientDataSource1" Height="400" Width="100%" Placeholder="select from the dropdown or type"
+
+    ClientDataSourceID="RadClientDataSource1"
+    
+    Height="400" Width="300px" Placeholder="select from the dropdown or type"
     DataTextField="ShipName" DataValueField="OrderID">
+    
     <VirtualSettings ItemHeight="28" ValueMapper="valueMapper" />
+    
     <ColumnsCollection>
         <telerik:MultiColumnComboBoxColumn Field="OrderID" Title="Order" Width="100" />
         <telerik:MultiColumnComboBoxColumn Field="ShipName" Title="Ship" Width="300" />
@@ -46,10 +107,12 @@ The following example shows how you can use virtualization with the service from
 </telerik:RadMultiColumnComboBox>
 
 <telerik:RadClientDataSource 
+
     EnableServerFiltering="true"
     EnableServerPaging="true"
     AllowPaging="true"
     PageSize="80"
+    
     ID="RadClientDataSource1" runat="server">
     <DataSource>
         <WebServiceDataSourceSettings ServiceType="OData" Select-DataType="JSON">