Question

我想更新一些实体而不先将它们加载到内存中。我知道这应该有效：

var myEntity = new MyEntity
{
    PkId = 123
};

myContext.Entry(myEntity).State = EntityState.Modified;
myEntity.ProcessTime = DateTime.Now;
myContext.SaveChanges();

但在致电SaveChanges时，我面临一些DbEntityValidationException，说明需要一些字段。我使用EF4（ObjectContext），但这从未发生过。此外，它只说明了3个必填字段，尽管有8个以上的必填字段。

在SaveChanges之前尝试过这个问题（没有运气）：

myContext.Entry(myEntity).Property(e=>e.ProcessTime).IsModified = true;

如果我使用_context.Configuration.ValidateOnSaveEnabled = false;，则SaveChanges不会抛出异常，但会更糟;它使用默认的clr值更新db-row！

我该怎么做？

我正在使用：

EF 6.1.3（数据库优先）
Oracle Data Provider NET 12c第4版
Visual Studio 2012
Windows 7 x64

Answer 1

最后，我发现这种令人厌恶（和错误）的方式有效：

var myEntity = new MyEntity
{
    PkId = 123
};

// If you skip this, the validation error occurs again.
// If you keep it, you might be killed.
myContext.Configuration.ValidateOnSaveEnabled = false; 

var dbEntry = myContext.Entry(myEntity);

// Let it think everything is just fine.
dbEntry.State = EntityState.UnChanged;

// If you have some fields already having updated value (before attaching),
// Inform it that it has been modified
// dbEntry.Property(r => r.YourProperty).IsModified = true;

// Change your field value.
// If you change a field, the state is already modified
// So, you don't need to tell it. Just change.
myEntity.ProcessTime = DateTime.Now;

// Call to save it and hope you did not forget to init any field value of any
// entity to be inserted in this context. If you did (mistakenly), it will remain
// silent and kill you later
myContext.SaveChanges();

如何在不提供所有字段的情况下更新分离的实体？

1 个答案: