我用c#和实体框架6（ef6）和mysql编写了一些代码。ide是VisualStudio2019预览版。
我安装了以下软件包：

<packages>
  <package id="EntityFramework" version="6.2.0" targetFramework="net461" />
  <package id="MySql.Data" version="6.10.8" targetFramework="net461" />
  <package id="MySql.Data.Entity" version="6.10.8" targetFramework="net461" />
</packages>

插入和选择是正确的，但更新有线工程。
我把一些数字（比如2或100）放入 tbx_CarId 我希望ef6只更新一行，但它会更新表中的每一行。

private void btn_update_Click(object sender, EventArgs e)
{
    using (MySqlConnection connection = new MySqlConnection(connectionString))
    {
        connection.Open();

        using (Parking context = new Parking(connection, false))
        {
            context.Database.Log = (string message) => { Console.WriteLine(message); };

            int targetId = Int32.Parse(tbx_CarId.Text);
            var blogs = from b in context.Cars
                        where b.CarId == targetId
                        select b;
            Car item = blogs.Single();
            item.Model = tbx_NewModel.Text;
            int numOfSavedLows = context.SaveChanges();
            Console.WriteLine("numOfSavedLows: " + numOfSavedLows.ToString());
        }
    }
}

方法 context.SaveChanges() 总是返回一个精确的数字1，并且在控制台窗口上打印“numofsavedlows:1”。
但是每当我执行这个方法时，每一行都会改变。
此外，ef6的记录器在控制台上写入如下内容：

Started transaction at 2019-01-03 오후 6:47:59 +09:00
`Car_Update`
-- CarId: '2' (Type = Int32, IsNullable = false)
-- Model: 'new value of the model' (Type = String, IsNullable = false, Size = 5)
-- Year: '2013' (Type = Int32, IsNullable = false)
-- Manufacturer: 'Dodge' (Type = String, IsNullable = false, Size = 5)
-- Executing at 2019-01-03 오후 6:47:59 +09:00
-- Completed in 6 ms with result: 16

Committed transaction at 2019-01-03 오후 6:47:59 +09:00
Disposed transaction at 2019-01-03 오후 6:47:59 +09:00

请看这条线 -- Completed in 6 ms with result: 16 数字（在本例中为16）是中每一行的计数 Car table。
为什么ef6每低更新一次？我该怎么修？
其余代码如下：

[DbConfigurationType(typeof(MySqlEFConfiguration))]
class Parking : DbContext
{
    public DbSet<Car> Cars { get; set; }

    public Parking()
      : base()
    {
        // constructor is empty
    }

    // Constructor to use on a DbConnection that is already opened
    public Parking(DbConnection existingConnection, bool contextOwnsConnection)
      : base(existingConnection, contextOwnsConnection)
    {
        // constructor is empty
    }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        modelBuilder.Entity<Car>().MapToStoredProcedures();
    }
}

以及

class Car
{
    public int CarId { get; set; }
    public string Model { get; set; }
    public int Year { get; set; }
    public string Manufacturer { get; set; }
}

大多数代码来自这里：https://dev.mysql.com/doc/connectors/en/connector-net-entityframework60.html
更新1：表格 Cars 看起来是这样的（模式和表是由ef6自动生成的）
更新2：行的值如下：before和after（args是8，'new value'）