Cannot implicitly convert type 'Word.ApplicationEvents2_DocumentBeforeSaveEventHandler' to 'Word.ApplicationEvents4_DocumentBeforeSaveEventHandler'

I have updated my version Microsoft Word Object Library from 15.0 to 16.0 and I am now getting the following error:

Cannot implicitly convert type
'Microsoft.Office.Interop.Word.ApplicationEvents2_DocumentBeforeSaveEventHandler'
to
'Microsoft.Office.Interop.Word.ApplicationEvents4_DocumentBeforeSaveEventHandler'

The code does the following:

`Word.Application wordApp = new Word.Application();

wordApp.DocumentBeforePrint += new             Word.ApplicationEvents2_DocumentBeforePrintEventHandler(wordApp_DocumentBeforePrint);`

I seem to have a mismatch between ApplicationEvents2 and ApplicationEvents4:

`namespace Microsoft.Office.Interop.Word
{
    [ComVisible(false)]
    [TypeLibType(16)]
    public delegate void ApplicationEvents2_DocumentBeforePrintEventHandler(Document Doc, ref bool Cancel);
}`
namespace Microsoft.Office.Interop.Word
{
    [ComEventInterface(typeof(ApplicationEvents4), typeof(ApplicationEvents4_EventProvider))]
    [ComVisible(false)]
    [TypeLibType(16)]
    public interface ApplicationEvents4_Event
    {
        event ApplicationEvents4_DocumentBeforePrintEventHandler DocumentBeforePrint;  
...
     }
}`

This error message says that the delegate type that you are trying to use for the DocumentBeforePrint event has changed in the updated version. The ApplicationEvents2_DocumentBeforePrintEventHandler delegate type has been changed to ApplicationEvents4_DocumentBeforePrintEventHandler.

Can try like this:

Word.Application wordApp = new Word.Application();
wordApp.DocumentBeforePrint += new Word.ApplicationEvents4_DocumentBeforePrintEventHandler(wordApp_DocumentBeforePrint);

Also, make sure to update the signature of the wordApp_DocumentBeforePrint to match the expected signature of the ApplicationEvents4_DocumentBeforePrintEventHandler delegate

Microsoft docs for ApplicationEvents4_DocumentBeforePrintEventHandler delegate