Web API on dependency injection

also you can run into race conditions, if check and insert are coded with the proper locking. You don't specify your concurrency requirements. EF supports optimistic concurrency if timestamps are used.

also not clear what the question has to do with the title.

How can I check if a record exists in the database before performing operations like editing or deleting it in a .NET Core Web API

Below is an action method generated automatically by the Visual Studio 2022 using a scaffolding operation for deleting a record. Note that it checks if a record exists in the database before performing deletion. You will able to check it like below.

// DELETE: api/Movies/5
[HttpDelete("{id}")]
public async Task<IActionResult> DeleteMovie(int id)
{
    var movie = await _context.Movie.FindAsync(id);
    if (movie == null)
    {
        return NotFound();
    }

    _context.Movie.Remove(movie);
    await _context.SaveChangesAsync();

    return NoContent();
}