'Populating a table in a .NET GUI View where a given User can only see a subset of rows returned by a Query

I have coded in .NET a GUI which includes a table populated by a Query. The table shows financial positions owned by different users identified in the application. I want a given user to only be able to see the rows showing her/his positions. How should I program that? I think it involves .NET Authorization features at a very granular level (see link below).

Applying Granular Right restriction in ASP.Net core



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