此连接的 EF Linq 查询的正确语法是什么
What is the right syntax for this joined EF Linq query
我正在尝试查询 returns 为我的 ViewModel 设置了正确格式的所有内容,这样我就不必从我的实体模型中手动复制所有内容。我有一个给我错误的 Linq 查询。 :
var query = from i in context.Invoices
join l in context.LineItems on i.InvoiceID equals l.InvoiceID into il
where i.InvoiceID == id
select new InvoiceViewModel()
{
InvoiceID = i.InvoiceID,
CustomerID = i.CustomerID,
InvoiceNote = i.Note,
InvoiceDate = i.InvoiceDate,
Terms = i.Terms,
LineItems = il.ToList<LineItemViewModel>()
};
这是我的视图模型
public class InvoiceViewModel {
public int InvoiceID { get; set; }
public int CustomerID { get; set; }
public string InvoiceNote { get; set; }
public DateTime InvoiceDate { get; set; }
public string Terms { get; set; }
public virtual ICollection<LineItemViewModel> LineItems { get; set; }
}
public class LineItemViewModel {
public int LineItemID { get; set; }
public int InvoiceID { get; set; }
public int Quantity { get; set; }
public string Item { get; set; }
public decimal Amount { get; set; }
public string LineItemNote { get; set; }
}
我得到的错误是(红色波浪线在 LineItems = il.ToList() 中的 il 下方)
'IEnumerable<LineItem>' does not contain a definition for 'ToList' and the best extension method overload 'Enumerable.ToList<LineItemViewModel>(IEnumerable<LineItemViewModel>)' requires a receiver of type 'IEnumerable<LineItemViewModel>'
我(有点,有点,有点)理解。那么正确的语法是什么?
您需要从 LineItem
实体明确初始化您的 LineItemViewModel
实例。你最好把它写成一个相关的子查询而不是一个连接:
var query =
from i in context.Invoices
where i.InvoiceID == id
select new InvoiceViewModel()
{
InvoiceID = i.InvoiceID,
CustomerID = i.CustomerID,
InvoiceNote = i.Note,
InvoiceDate = i.InvoiceDate,
Terms = i.Terms,
LineItems =
(
from li in context.LineItems
where li.InvoiceID == i.InvoiceID
select new LineItemViewModel
{
LineItemID = li.LineItemID,
InvoiceID = li.InvoiceID,
Quantity = li.Quantity,
Item = li.Item,
Amount = li.Amount,
LineItemNote = li.LineItemNote,
}
).ToList()
};
我正在尝试查询 returns 为我的 ViewModel 设置了正确格式的所有内容,这样我就不必从我的实体模型中手动复制所有内容。我有一个给我错误的 Linq 查询。 :
var query = from i in context.Invoices
join l in context.LineItems on i.InvoiceID equals l.InvoiceID into il
where i.InvoiceID == id
select new InvoiceViewModel()
{
InvoiceID = i.InvoiceID,
CustomerID = i.CustomerID,
InvoiceNote = i.Note,
InvoiceDate = i.InvoiceDate,
Terms = i.Terms,
LineItems = il.ToList<LineItemViewModel>()
};
这是我的视图模型
public class InvoiceViewModel {
public int InvoiceID { get; set; }
public int CustomerID { get; set; }
public string InvoiceNote { get; set; }
public DateTime InvoiceDate { get; set; }
public string Terms { get; set; }
public virtual ICollection<LineItemViewModel> LineItems { get; set; }
}
public class LineItemViewModel {
public int LineItemID { get; set; }
public int InvoiceID { get; set; }
public int Quantity { get; set; }
public string Item { get; set; }
public decimal Amount { get; set; }
public string LineItemNote { get; set; }
}
我得到的错误是(红色波浪线在 LineItems = il.ToList() 中的 il 下方)
'IEnumerable<LineItem>' does not contain a definition for 'ToList' and the best extension method overload 'Enumerable.ToList<LineItemViewModel>(IEnumerable<LineItemViewModel>)' requires a receiver of type 'IEnumerable<LineItemViewModel>'
我(有点,有点,有点)理解。那么正确的语法是什么?
您需要从 LineItem
实体明确初始化您的 LineItemViewModel
实例。你最好把它写成一个相关的子查询而不是一个连接:
var query =
from i in context.Invoices
where i.InvoiceID == id
select new InvoiceViewModel()
{
InvoiceID = i.InvoiceID,
CustomerID = i.CustomerID,
InvoiceNote = i.Note,
InvoiceDate = i.InvoiceDate,
Terms = i.Terms,
LineItems =
(
from li in context.LineItems
where li.InvoiceID == i.InvoiceID
select new LineItemViewModel
{
LineItemID = li.LineItemID,
InvoiceID = li.InvoiceID,
Quantity = li.Quantity,
Item = li.Item,
Amount = li.Amount,
LineItemNote = li.LineItemNote,
}
).ToList()
};