Entity Framework Core 6 - 多对多更新

Question

I'm trying to create a update for EF Core 6 many-to-many on SQL Server but I am really confused. I have stock.cs class and location.cs class

public class Stock : BaseModel 
{
    public Stock()
    {
        this.Locations = new List<Location>();
    }

    [Key] 
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public string Guid { get; set; } = string.Empty;
    public string RackBarNumber { get; set; } = string.Empty;
    public string ShelveNumber { get; set; } = string.Empty;
    public string ShelveName { get; set; } = string.Empty;

    public virtual List<Location>? Locations { get; set; }
}

public class Location : BaseModel
{
    public Location()
    {
        this.Stocks = new List<Stock>();
    }

    [Key] 
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public string? Description { get; set; }

    public virtual List<Stock>? Stocks { get; set; }
}

I use this as my DTO for getting all my current locations

public class StockLocations
{
    public Stock Stock { get; set; }
    public virtual ICollection<Location> currentLocations { get; set; }
}

Now the StockController is the piece of code which updates the fields, I am able to create and delete in the StockLocation table that EF Core creates. But when I try many updates at once it just goes haywire.

This is my last attempt:

[HttpPut("{id}")]
public async Task<IActionResult> PutStock(int id, StockLocations stockLocation)
{
    await _userService.ConfirmUser(User);
        
    stockLocation.Stock.UpdatedAt = DateTime.Now;
        
    List<Location> removedLocations = new List<Location>();

    if (id != stockLocation.Stock.Id)
    {
        return BadRequest();
    }

    _context.Entry(stockLocation.Stock).State = EntityState.Modified;

    try
    {
        await _context.SaveChangesAsync();
            
        // Add new items to the database
        foreach (var item in stockLocation.Stock.Locations)
        {
            if (!stockLocation.currentLocations.Any(x => x.Id == item.Id))
            {
                _context.Entry(item).State = EntityState.Modified;
                await _context.SaveChangesAsync();
            }
        }
            
        // Create a list of removed locations to be removed from the database
        foreach (Location location in stockLocation.currentLocations)
        {
            if (!stockLocation.Stock.Locations.Any(x => x.Id == location.Id))
            {
                removedLocations.Add(location);
            }
        }

        foreach (var item in removedLocations)
        {
            /*
            Stock stock = _context.Stocks.Include(x => x.Locations).Single(x =>             x.Id == id);
            Location locationToDelete = stock.Locations.Find(x => x.Id == item.Id);

            stock.Locations.Remove(locationToDelete);
            await _context.SaveChangesAsync();
            */
        }
    }
    catch (DbUpdateConcurrencyException)
    {
        return NoContent();
    }

    return NoContent();
}

Anyone who is willing to tell me how I can approach this properly?

Answer 1

Since you need to update StockLocations I will recommend that tyou just pull the record from the database such as:

        var record = await  _context.StockLocations
            .Include(a=>a.Location).Include(a=>a.Stock)
            .FirstOrDefaultAsync(a=>a.id == id);  
    
        if(record == null) {
        thrown new NotFoundException(); 
        }  
    
    stockLocation.Stock.UpdatedAt = DateTime.Now; 
     await _context.SaveChangesAsync(); 

 // other code  
 // add new location to the db if they don't exist 
 var locations = stockLocation.Location; 
  foreach(var loc in locations) {
    var findLocation = 
    _context.Locations.FirstOrDefault(a=>a.Name.ToLower() == 
   loc.Name.ToLower()) ; 
   if(findLocation == null){
  // does not exist and can be added 
   } 

}