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[英]How to update tables in many-to-many relationship in Entity Framework Core?
[英]Update is not working for many-to-many relationship. Entity Framework Core 2.2
我在游戏和类别之间有很多关系。 我正在使用Sql Server 。 一款游戏可以有多个类别。 创建操作有效但更新无效。 得到一个错误:
InnerException:违反 PRIMARY KEY 约束“PK_GameCategories”。 无法在对象“dbo.GameCategories”中插入重复键。 重复的键值为 (1003, 1)。\\r\\n语句已终止。
public class Game
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
[Display(Name = "Game Name")]
public string Name { get; set; }
[Display(Name = "Game Categories")]
public ICollection<GameCategory> GameCategories { get; set; }
}
public class Category
{
[Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
[Display(Name = "Game Category")]
public string Name { get; set; }
[Display(Name = "Game Categories")]
public ICollection<GameCategory> GameCategories { get; set; }
}
public class GameCategory
{
public int GameId { get; set; }
public Game Game { get; set; }
public int CategoryId { get; set; }
public Category Category { get; set; }
}
// --------------------------
GameController/Edit Action [Working Perfectly]
// -------------------------
[HttpGet]
[Route("edit-game/{id}")]
public async Task<IActionResult> EditGame(int id)
{
try
{
if (id == null) return NotFound();
var gameInDb = await _db.Games.FirstOrDefaultAsync(g => g.Id == id);
if (gameInDb == null) return NotFound();
var model = new GameChangeViewModel()
{
Title = $"Edit {gameInDb.Name}",
Name = gameInDb.Name,
// Displaying list of categories
GameCategoryList = _db.Categories
.Select(c => new SelectListItem() { Text = c.Name, Value = c.Id.ToString()}).ToList(),
// loading selected values
GameCategoryId = _db.GameCategories.Where(c=>c.GameId == gameInDb.Id).Select(s=>s.CategoryId).ToList()
};
return View(model);
}
catch (Exception e)
{
Console.WriteLine(e);
return NotFound();
}
}
以下代码不起作用并引发上述异常。
[HttpPost]
[Route("edit-game-post")]
[ValidateAntiForgeryToken]
public async Task<IActionResult> EditGamePost(GameChangeViewModel model)
{
try
{
if (!ModelState.IsValid) return View(nameof(EditGame), model);
var gameInDb = await _db.Games.FirstOrDefaultAsync(g => g.Id == model.Id);
if (gameInDb == null)
{
ModelState.AddModelError("", "No Data");
return View(nameof(EditGame), model);
}
_db.GameCategories.RemoveRange(gameInDb.GameCategories);
_db.SaveChanges();
gameInDb.Name = model.Name;
var category = _db.Categories.Where(c => model.GameCategoryId.Contains(c.Id)).ToList();
foreach (Category cat in category)
{
gameInDb.GameCategories.Add(new GameCategory()
{
Category = cat, Game = gameInDb
});
}
await _db.SaveChangesAsync();
return RedirectToAction(nameof(Index));
}
catch (Exception e)
{
Console.WriteLine(e);
ModelState.AddModelError("", "Exception Happen");
return View(nameof(EditGame), model);
}
}
不幸的是,我还没有在多对多关系中找到任何合适的 CRUD 操作。 谢谢
尝试在 GameCategory 表中创建新的列 ID 作为主键。
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