最近，我正在尝试将EF5升级为EF6样本项目。示例项目的表格有十进制(5,2)类型的列。数据库迁移成功完成。但是，初始数据种子产生了异常。

模型:

    public partial class Weather
    {
    ...
    public decimal TMax {get;set;}
    public decimal TMin {get;set;}
    ...
    }

配置错误:

public partial class WeatherMap : EntityTypeConfiguration<Weather>
{

    public WeatherMap()
    {
        ...
        this.Property(t => t.TMax).HasColumnName("TMax");
        this.Property(t => t.TMin).HasColumnName("TMin");
        ...
    }
}

数据:

    internal static Weather[] data = new Weather[365]
    {
      new Weather() {...,TMax = 3.30M,TMin = -12.00M,...},
      new Weather() {...,TMax = 5.20M,TMin = -10.00M,...},
      new Weather() {...,TMax = 3.20M,TMin = -8.00M,...},
      new Weather() {...,TMax = 11.00M,TMin = -7.00M,...},
      new Weather() {...,TMax = 9.00M,TMin = 0.00M,...},
    };

我发现了问题，播种数据有精度值，但配置没有精度和比例参数。在样本表中用十进制(10,0)定义的TMax和TMin字段。

正确配置:

public partial class WeatherMap : EntityTypeConfiguration<Weather>
{

    public WeatherMap()
    {
        ...
        this.Property(t => t.TMax).HasPrecision(5,2).HasColumnName("TMax");
        this.Property(t => t.TMin).HasPrecision(5,2).HasColumnName("TMin");
        ...
    }
}

我的示例项目运行在:MySql 5.6.14, Devart.Data。MySql, MVC4， .Net 4.5.1, EF6.01

致以最亲切的问候。

检查你是否忘记了GridView中的“DataKeyNames”属性。 当在GridView中修改数据时，它是必须的

http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.gridview.datakeynames.aspx

该问题是由以下两种原因之一引起的:-

You tried to update a row with one or more properties are Concurrency Mode: Fixed .. and the Optimistic Concurrency prevented the data from being saved. Ie. some changed the row data between the time you received the server data and when you saved your server data. You tried to update or delete a row but the row doesn't exist. Another example of someone changing the data (in this case, removing) in between a retrieve then save OR you're flat our trying to update a field which is not an Identity (ie. StoreGeneratedPattern = Computed) and that row doesn't exist.

我有这个问题与Mvc身份注册新用户，而不是:

var result = await UserManager.CreateAsync(user);

我正在做:

var result = await UserManager.UpdateAsync(user);

我得到了同样的错误，因为PK的一部分是datetime列，而插入的记录使用了datetime。现在作为这一列的值。实体框架将以毫秒级精度插入值，然后以毫秒级精度查找刚刚插入的值。然而，SqlServer将该值舍入到秒精度，因此实体框架无法找到毫秒精度值。

解决方案是截断DateTime中的毫秒。在插入之前。

我也面临着同样可怕的错误……:)然后我意识到我忘记设置一个

@Html。HiddenFor(model => model. userprofile . userid)

用于更新对象的主键!我容易忘记这个简单但非常重要的事情!

顺便说一下:HiddenFor是ASP的。净MVC。