Question

我有多个对象，包含表中的字段子集。在某些情况下，我应该只更新一个字段。如何在Entity Framework 6.0中正确执行此操作？由于数据库限制，以下代码引发错误，因为AddOrUpdate尝试将所有字段替换为FieldName除空值。

public static TheField Set(TheField f)
{
    using (var dbContext = new MyModel())
    {
            dbContext.MyEntity.AddOrUpdate(new MyEntity()
            {
                ForeignId = f.ForeignId,
                FieldName = f.FieldName,
            });
            dbContext.SaveChanges();

            return f;
    }
}

有一个扩展

会很高兴

public static class MyExtension
{
    public static void AddOrUpdateSchema<TEntity, TKey>(this IDbSet<TEntity> set, TKey id, string schema, 
        params TEntity[] entities) where TEntity : class
    {
        // ...
    }
}

然后使用它

public class MyEntity
{
    [Key]
    public int ForeignId { get; set; }

    [UpdateSchema("Schema")]
    public string FieldName { get; set; }
    // ...
}

public class MyEntityView
{
    public int ForeignId { get; set; }
    public string FieldName { get; set; }

    public static MyEntityView Set(MyEntityView f)
    {
        using (var dbContext = new MyModel())
        {
            dbContext.MyEntity.AddOrUpdateSchema(f.ForeignId, "Schema", new MyEntity()
            {
                FieldName = f.FieldName,
            });
            dbContext.SaveChanges();

            return f;
        }
    }
}

或者Entity Framework是否已具备此任务的功能？

Answer 1

将State属性设置为EntityState.Modified

db.Entry(entity).State = EntityState.Modified;

Answer 2

请检查以下代码是否适合您：

using (var dbContext = new MyModel())
{   
    if (dbContext.MyEntities.Any(e => e.ForeignId == f.ForeignId))
    {
        dbContext.MyEntities.Attach(f);
        dbContext.ObjectStateManager.ChangeObjectState(f, EntityState.Modified);
    }
    else
    {
        dbContext.MyEntities.AddObject(f);
    }

    dbContext.SaveChanges();
}

如何使用Entity Framework更新字段子集？

2 个答案: