EF:按Id更新字段的最佳/最快方式

using (var context = new YourDbContext())
{
    var entity = context.YourDbSet.Find(id);
    if (entity != null)
    {
        entity.FieldName = newValue;
        context.SaveChanges();
    }
}

using (var context = new YourDbContext())
{
    var entity = new YourEntity { Id = id };
    context.YourDbSet.Attach(entity);
    entity.FieldName = newValue;
    context.Entry(entity).State = EntityState.Modified;
    context.SaveChanges();
}

using (var context = new YourDbContext())
{
    var entity = new YourEntity { Id = id };
    entity.FieldName = newValue;
    context.YourDbSet.Update(entity);
    context.SaveChanges();
}