How do I run EF Core ExecuteUpdateAsync and add a new entity as part of that update?

ExecuteUpdateAsync will try to create a SQL query based on the c# code you write. In the c# code, you are trying to update two tables at the same time in the same query. It's not possible. Even with writing your own SQL, most DMBS, don't allow it. (with exception of MySQL)

From your error message

The following lambda argument to 'SetProperty' does not represent a valid property to be set: 'p => p.YogabandyFee'

it seems like the parser is looking for a property instead of an object, so, hence, I tried to set the TotalFee of the YogabandyFee:

var payoutResult = await _dbContext.StripePayouts
            .Where(p => p.StripePayoutId == stripePayoutId)
            .Select(p => new { p.GrossAmount, p.TotalTokens, p.NetAmount, p.ReconciledTransfers, p.EditedDate, p.YogabandyFee })
            .ExecuteUpdateAsync(setters => setters
                .SetProperty(p => p.GrossAmount, grossAmount)
                .SetProperty(p => p.TotalTokens, totalTokens)
                .SetProperty(p => p.YogabandyFee.TotalFee, p => grossAmount - p.NetAmount - platformFee )
                .SetProperty(p => p.ReconciledTransfers, true)
                .SetProperty(p => p.EditedDate, DateTime.UtcNow)
            );

And you'll see this error:

Multiple 'SetProperty' invocations refer to different tables ('p => p.YogabandyFee.TotalFee' and 'p => p.EditedDate'). A single 'ExecuteUpdate' call can only update the columns of a single table.

What I'm trying to say is: ExecuteUpdate can only update one table. I think, the answer to "Can I create a new entry in this type of update?" is no.

My suggestions:

1. Use stored procedures to update both tables at once (https://stackoverflow.com/a/5154670/17431983); tools like Dapper allow you run a stored procedure.
2. Use UnitOfWork - this allows you to do multiple _dbContext queries in the same transaction

You can also do two separate ExecuteUpdateAsync, one for each table update, if it's not a performance issue.

If you are updating only one StripePayout object and it's small, I think using SaveChanges() suits more.

class Program
{
    static async Task Main(string[] args)
    {
        // await FillDatabase();
        await UpdateStripePayout(1, 1000m, 50, 50m);
    }

    private static async Task FillDatabase()
    {
        using var _dbContext = new AppDbContext();
        
        await _dbContext.StripePayouts.AddAsync(new StripePayout()
        {
            EditedDate = new DateTime(),
            GrossAmount = new decimal(123.4),
            NetAmount = new decimal(123.4),
            ReconciledTransfers = false,
            StripePayoutId = 1,
            TotalTokens = 10,
            YogabandyFee = new YogabandyFee()
        });
        
        await _dbContext.SaveChangesAsync();
    }

    public static async Task UpdateStripePayout(int stripePayoutId, decimal grossAmount, int totalTokens, decimal platformFee)
    {
        using var _dbContext = new AppDbContext();
        
        var payoutResult = await _dbContext.StripePayouts
                .FirstOrDefaultAsync(p => p.StripePayoutId == stripePayoutId);

        if (payoutResult == null)
        {
            return; // You can raise an error here if you like
        }
        
        payoutResult.GrossAmount = grossAmount;
        payoutResult.TotalTokens = totalTokens;
        payoutResult.ReconciledTransfers = true;
        payoutResult.EditedDate = DateTime.UtcNow;
        payoutResult.YogabandyFee = new YogabandyFee()
            { TotalFee = (grossAmount - payoutResult.NetAmount - platformFee) };

        _dbContext.Update(payoutResult);
        await _dbContext.SaveChangesAsync();

        var newResult = await _dbContext.StripePayouts.FirstAsync(p => p.StripePayoutId == stripePayoutId);
        Console.WriteLine(newResult.YogabandyFee.TotalFee);
    }
}

I also found this on Microsoft docs: https://learn.microsoft.com/en-us/ef/core/saving/

If you need to manipulate a graph of objects (i.e. multiple interconnected objects), use SaveChanges; it will figure out the proper ordering of the changes and how to link everything together. "I want to update a blog, changing some of its posts and deleting others"