你应该删除db.Books.Attach(book);

您正在尝试更新记录(对我来说这意味着“更改现有记录上的值并将其保存回来”)。因此，您需要检索对象，进行更改并保存它。

using (var db = new MyContextDB())
{
    var result = db.Books.SingleOrDefault(b => b.BookNumber == bookNumber);
    if (result != null)
    {
        result.SomeValue = "Some new value";
        db.SaveChanges();
    }
}

试一试……

UpdateModel(图书);

var book = new Model.Book
{
    BookNumber =  _book.BookNumber,
    BookName = _book.BookName,
    BookTitle = _book.BookTitle,
};
using (var db = new MyContextDB())
{
    var result = db.Books.SingleOrDefault(b => b.BookNumber == bookNumber);
    if (result != null)
    {
        try
        {
            UpdateModel(book);
            db.Books.Attach(book);
            db.Entry(book).State = EntityState.Modified;
            db.SaveChanges();
        }
        catch (Exception ex)
        {
            throw;
        }
    }
}

以下是我的后ria实体更新方法(Ef6时间框架):

public static void UpdateSegment(ISegment data)
{
    if (data == null) throw new ArgumentNullException("The expected Segment data is not here.");

    var context = GetContext();

    var originalData = context.Segments.SingleOrDefault(i => i.SegmentId == data.SegmentId);
    if (originalData == null) throw new NullReferenceException("The expected original Segment data is not here.");

    FrameworkTypeUtility.SetProperties(data, originalData);

    context.SaveChanges();
}

注意FrameworkTypeUtility.SetProperties()是我在NuGet上AutoMapper之前写的一个小工具函数:

public static void SetProperties<TIn, TOut>(TIn input, TOut output, ICollection<string> includedProperties)
    where TIn : class
    where TOut : class
{
    if ((input == null) || (output == null)) return;
    Type inType = input.GetType();
    Type outType = output.GetType();
    foreach (PropertyInfo info in inType.GetProperties())
    {
        PropertyInfo outfo = ((info != null) && info.CanRead)
            ? outType.GetProperty(info.Name, info.PropertyType)
            : null;
        if (outfo != null && outfo.CanWrite
            && (outfo.PropertyType.Equals(info.PropertyType)))
        {
            if ((includedProperties != null) && includedProperties.Contains(info.Name))
                outfo.SetValue(output, info.GetValue(input, null), null);
            else if (includedProperties == null)
                outfo.SetValue(output, info.GetValue(input, null), null);
        }
    }
}

我找到了一个很好的方法。

 var Update = context.UpdateTables.Find(id);
        Update.Title = title;

        // Mark as Changed
        context.Entry(Update).State = System.Data.Entity.EntityState.Modified;
        context.SaveChanges();

当尝试使用Attach()和SaveChanges()组合更新记录时，我也有同样的问题，但我使用的是SQLite DB及其EF提供者(相同的代码在SQLServer DB中工作没有问题)。

I found out, when your DB column has GUID (or UniqueIdentity) in SQLite and your model is nvarchar, SQLIte EF treats it as Binary(i.e., byte[]) by default. So when SQLite EF provider tries to convert GUID into the model (string in my case) it will fail as it will convert to byte[]. The fix is to tell the SQLite EF to treat GUID as TEXT (and therefore conversion is into strings, not byte[]) by defining "BinaryGUID=false;" in the connectionstring (or metadata, if you're using database first) like so:

  <connectionStrings>
    <add name="Entities" connectionString="metadata=res://savetyping...=System.Data.SQLite.EF6;provider connection string=&quot;data source=C:\...\db.sqlite3;Version=3;BinaryGUID=false;App=EntityFramework&quot;" providerName="System.Data.EntityClient" />
  </connectionStrings>

链接到对我有效的解决方案: SQLite实体框架6提供者如何处理指南?