In ASP.NET Core MVC, the 'RenderAction' method is not available by default. You can use similar functionalities using 'PartialViewResult' and Partial or 'ViewComponent', examples given at -
RenderPartial vs RenderAction vs Partial vs Action in MVC[
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If you only want to use partial view within the current view -
@await Html.PartialAsync("NewOrder", "Order")
Alternatively, if you want to use a view component, you can create a view component and then call it in your view -
@await Component.InvokeAsync("NewOrder", new { /* optional parameters */ })