The ribbon added to a VSTO for Excel is of type RibbonBase and not IRibbonExtensibility

Question

I am building a VSTO application (WinForms) and following the instructions at:

https://docs.microsoft.com/en-us/visualstudio/vsto/walkthrough-creating-a-custom-tab-by-using-ribbon-xml?view=vs-2019

The steps are shown below:

On the Project menu, click Add New Item.
In the Add New Item dialog box, select Ribbon (XML).
Change the name of the new Ribbon to MyRibbon, and click Add. The MyRibbon.cs or MyRibbon.vb file opens in the designer. An XML file that is named MyRibbon.xml is also added to your project.
In Solution Explorer, right-click ThisAddin.cs or ThisAddin.vb, and then click View Code.
Add the following code to the ThisAddin class. This code overrides the CreateRibbonExtensibilityObject method and returns the Ribbon XML class to the Office application.

When I add the CreateRibbonExtensibilityObject() code in step 5 (shown below):

protected override Microsoft.Office.Core.IRibbonExtensibility CreateRibbonExtensibilityObject()
        {
            return new MyRibbon();
        }

I get the following error:

Cannot implicitly convert the type MyRibbon to Microsoft.Office.Core.IRibbonExtensibility. An explicit conversion exists (are you missing a cast)?

The class generated by Visual Studion is of type RibbonBase.

 partial class CLIREMPRibbon : Microsoft.Office.Tools.Ribbon.RibbonBase {...}

A type-cast below throws an exception:

Unable to cast object of type MyRibbon to type Microsoft.Office.Core.IRibbonExtensibility.

How would I apply the correct type cast of a RibbonBase to a IRibbonExtensibility interface instance?

Eugene Astafiev Eugene Astafiev · Accepted Answer · 2020-07-12T19:14:24

In VSTO, you can create a basic custom Fluent UI using a visual designer and then export it to a ribbon XML file which can be extended after. Not all features are available in the ribbon designer, unfortunately, so sometimes you have to switch to using the raw XML markup instead. Read more about that in the How to: Export a ribbon from the Ribbon Designer to Ribbon XML article. So, if you are fine with a designer, there is no need to modify anything in the code. You have to choose one or another way of customizing the Fluent UI.

The ribbon added to a VSTO for Excel is of type RibbonBase and not IRibbonExtensibility

2 Answers