Question

我的查找表存在问题。我有一个表单，允许我从列表中选择颜色，该列表将成为团队的一部分。更新方法如下所示：

[HttpPut]
[Route("")]
/// <summary>
/// Update a team
/// </summary>
/// <param name="model">The team model</param>
/// <returns>Nothing</returns>
public async Task<IHttpActionResult> Update(TeamBindingViewModel model)
{

    // If our model is invalid, return the errors
    if (!ModelState.IsValid)
        return BadRequest(ModelState);

    // Get our current team
    var team = await this.service.GetAsync(model.Id, "Colours");

    // Make changes to our team
    team.Name = model.Name;
    team.Sport = model.Sport;

    // Find out which colours need adding and removing
    var coloursToRemove = GetDifference(team.Colours, model.Colours);
    var coloursToAdd = GetDifference(model.Colours, team.Colours);

    // Loop through our colours to remove and remove them
    if (coloursToRemove.Count() > 0)
        foreach (var colour in coloursToRemove)
            team.Colours.Remove(colour);

    // Loop through the colours to add and add them
    if (coloursToAdd.Count() > 0)
        foreach (var colour in coloursToAdd)
            team.Colours.Add(colour);

    // Update the team
    this.service.Update(team);

    // Save the database changes
    await this.unitOfWork.SaveChangesAsync();

    // Return Ok
    return Ok(model);
}

private IList<Colour> GetDifference(IList<Colour> firstList, IList<Colour> secondList)
{

    // Create a new list
    var list = new List<Colour>();

    // Loop through the first list
    foreach (var first in firstList)
    {

        // Create a boolean and set to false
        var found = false;

        // Loop through the second list
        foreach (var second in secondList)
        {

            // If the first item id is the same as the second item id
            if (first.Id == second.Id)
            {

                // Mark it has being found
                found = true;
            }
        }

        // After we have looped through the second list, if we haven't found a match
        if (!found)
        {

            // Add the item to our list
            list.Add(first);
        }
    }

    // Return our differences
    return list;
}

如果我在 unitOfWork.SaveChangesAsync（）上放置一个断点，那么我可以看到团队颜色正在使用我数据库中已有的颜色（所有id匹配起来。但是一旦 SaveChangesAsync 执行，它就会在Colors表中创建一个新行，其中包含我刚刚选择的颜色的副本。我不希望它创建一个新行，我希望它使用所选的颜色。

我不确定如何提供更多信息;我希望这足以说明某人能够帮助我！

更新

所以我决定查看生成的SQL。我的 Colors 表中有一种颜色，如下所示：

10 Red（Pms200）ff0000

所以 ID 10 ，名称是红色（Pms200）和十六进制是 ff0000 。如果我在编辑团队时选择该颜色并按提交。它运行上面显示的 Update 方法，我已经改变了我的 DbContext ，通过在构造函数中添加以下行来记录sql：

this.Database.Log = s => Debug.WriteLine(s);

因此，当 SaveChangesAsync 代码出现时，会生成以下SQL：

Started transaction at 13/04/2015 12:25:03 +01:00

UPDATE [dbo].[Teams]
SET [Name] = @0, [Sport] = @1
WHERE ([Id] = @2)

-- @0: 'Testing' (Type = String, Size = -1)

-- @1: 'ultimate-frisbee' (Type = String, Size = -1)

-- @2: '1' (Type = Int32)

-- Executing asynchronously at 13/04/2015 12:25:03 +01:00

-- Completed in 5 ms with result: 1



INSERT [dbo].[Colours]([Name], [Hex])
VALUES (@0, @1)
SELECT [Id]
FROM [dbo].[Colours]
WHERE @@ROWCOUNT > 0 AND [Id] = scope_identity()


-- @0: 'Red (Pms200)' (Type = String, Size = -1)

-- @1: 'ff0000' (Type = String, Size = -1)

-- Executing asynchronously at 13/04/2015 12:25:03 +01:00

-- Completed in 1 ms with result: SqlDataReader



INSERT [dbo].[TeamColours]([TeamId], [ColourId])
VALUES (@0, @1)

-- @0: '1' (Type = Int32)

-- @1: '43' (Type = Int32)

-- Executing asynchronously at 13/04/2015 12:25:03 +01:00

-- Completed in 1 ms with result: 1



Committed transaction at 13/04/2015 12:25:03 +01:00

Closed connection at 13/04/2015 12:25:03 +01:00

现在的问题是它应该只在 TeamColours 表中插入一些内容而不是 Colors 表。我无法弄清楚为什么......

因为有人要求查看我的 UnitOfWork 课程，所以这是：

public class UnitOfWork<TContext> : IUnitOfWork where TContext : DbContext, new()
{
    private readonly DbContext context;
    private Dictionary<Type, object> repositories;

    public DbContext Context { get { return this.context; } }

    public UnitOfWork()
    {
        this.context = new TContext();
        repositories = new Dictionary<Type, object>();
    }

    public IRepository<TEntity> GetRepository<TEntity>() where TEntity : class
    {
        if (repositories.Keys.Contains(typeof(TEntity)))
            return repositories[typeof(TEntity)] as IRepository<TEntity>;

        var repository = new Repository<TEntity>(context);

        repositories.Add(typeof(TEntity), repository);

        return repository;
    }

    public async Task SaveChangesAsync()
    {
        try
        {
            await this.context.SaveChangesAsync();
        }
        catch (DbUpdateConcurrencyException ex)
        {
            ex.Entries.First().Reload();
        }
    }

    public void Dispose()
    {
        this.context.Dispose();
    }
}

虽然我确信这不会导致问题。

Answer 1

Model.Colors与上下文无关。所以你的Db Context试图添加新的。

1 - 从存储库中获取颜色

var newColours = repository.ListColours(model.Colors.Select(m=>m.Id));

2-为团队分配新颜色

team.Colours = newColours;

this.service.Update(team);

await this.unitOfWork.SaveChangesAsync();

EF将自动执行删除和添加操作。

我还没有测试过这段代码。但我希望EntityFramework比我更聪明。

实体框架更新查找表正在向另一个表添加项目

1 个答案: