I made a ticket on this but thought I would post here as well.

It appears there is an issue with the latest Telerik Blazor version when it comes to adding new grid items.

I can't get it to work in my project and can't get it to work in your demo either.

https://demos.telerik.com/blazor-ui/grid/editing-inline 

Click add new employee.

Fill the info boxes.

View the added row. The Name field is empty.

I stepped through the code in my project and the parameter from the field is always null.

To post here for the community too - I have logged this for fixing and you can track its status in the following page: https://feedback.telerik.com/blazor/1410617-string-field-is-blank-when-saving-a-new-row-in-edge.

At the moment we are focusing on compatibility with Preview6 which brought a lot of (breaking) changes. I'm afraid I cannot provide an ETA on this particular fix at the moment. You can click the Follow button on the bug report page and you will get email notifications when its status changes. At the moment, it is "Approved", which, for a bug, means that we acknowledge it is a problem in the product and we intend to fix it. It will change to "Scheduled" or "Completed" when it is fixed and a release will appear below it. You can find a legend of the statuses by hovering the question mark icon next to the Status header in the right hand side navigation.