"dynamic" data type is recognized as "object" when using Excel COM

I have the following simple code which defines last cell with non-empty data, defines its row and gets its value:

using Excel = Microsoft.Office.Interop.Excel;

Excel.Application xlApp = new Excel.Application { Visible = true };
Excel.Workbook xlBook = xlApp.Workbooks[1];
Excel.Worksheet sheet = xlBook.Sheets[1] as Excel.Worksheet;
int lastRow = sheet.Cells[sheet.Rows.Count, "Q"].End[Excel.XlDirection.xlUp].Row;
dynamic value = sheet.Cells[lastRow, "Q"].Value;

When I’m building the project using .NET 5 (5.0.101 or 5.0.200-preview.20601.7 SDK), I get the following two errors in Output window:

error CS1061: ‘object’ does not contain a definition for ‘End’ and no accessible extension method ‘End’ accepting a first argument of type ‘object’ could be found (are you missing a using directive or an assembly reference?)

error CS1061: ‘object’ does not contain a definition for ‘Value’ and no accessible extension method ‘Value’ accepting a first argument of type ‘object’ could be found (are you missing a using directive or an assembly reference?)

Here are problems:

1. When I’m using .NET Framework 4.8, the project is built fine without any errors and code executes perfectly. In .NET 5, however, the dynamic data type is somehow recognized as object.
2. I emphasized “in Output window”, because now errors do not show up in “Error List” anymore - they are now seen in “Output” window. For instance, if I remove last semicolon in my code, no errors appear in “Error List”. Instead, I should build project first, and only then error appears, but in “Output” window rather than “Error List” window.

Visual Studio Version: 16.9.0 Preview 2.0

[jaredpar]

@terrajobst helpfully figured out what I was missing and created a repro. The part I was missing is that it needs to be a WPF project. In that case the reference is not passed as EmbedInteropTypes.

Moving to the WPF repo for triage.

[ryalanms]

Thank you @JohnyL and @jaredpar for the report and investigation. Capitalizing the ‘T’ worked for me locally.

    <ItemGroup>
             ...
            <EmbedInteropTypes>True</EmbedInteropTypes>
        </COMReference>
    </ItemGroup>