[英]Can't Add Model to List
I perform the following for each
loop to insert models into a list: 我for each
循环执行以下操作以将模型插入到列表中:
Dim weights = weight.Where(Function(x) x.FW_Food_ID = item.NDB_No)
For Each i In weights
Dim model = New Tbl_Food_Weight
model.FW_GmWt = i.FW_GmWt
Debug.Print("i.FW_GmWt=" + i.FW_GmWt)
Debug.Print("model.FW_GmWt=" + model.FW_GmWt)
model.FW_Food_ID = i.FW_Food_ID
Debug.Print("i.FW_Food_ID=" + i.FW_Food_ID)
Debug.Print("model.FW_Food_ID=" + model.FW_Food_ID)
model.FW_Option = i.FW_Option
Debug.Print("i.FW_Option=" + i.FW_Option)
Debug.Print("model.FW_Option=" + model.FW_Option)
model.FW_ID = i.FW_ID
Debug.Print("i.FW_ID=" + i.FW_ID.ToString)
Debug.Print("model.FW_ID=" + model.FW_ID.ToString)
item.test.Add(model)
Next
My model is as follows: 我的模型如下:
Public Class Tbl_Food_Weight
<Key()> _
Public Property FW_ID As Integer
Public Property FW_Food_ID As String
Public Property FW_Option As String
Public Property FW_Serving_Size As String
Public Property FW_GmWt As String
End Class
My test
property is as follows: 我的test
属性如下:
<NotMapped()> _
Public Overridable Property test As List(Of Tbl_Food_Weight)
The output that I get is: 我得到的输出是:
i.FW_GmWt=250
model.FW_GmWt=250
i.FW_Food_ID=12695
model.FW_Food_ID=12695
i.FW_Option=1
model.FW_Option=1
i.FW_ID=4481
model.FW_ID=4481
A first chance exception of type 'System.NullReferenceException' occurred in MyBlog.DLL
The error occurs on this line: 此行发生错误:
item.test.Add(model)
You see, it puts in the variables, but when I go to add the model to the list, it says it's null. 你看,它放入了变量,但是当我把模型添加到列表中时,它说它是空的。 How can I add the model to the list of models? 如何将模型添加到模型列表中?
Thank you. 谢谢。
Edit: 编辑:
Item in context: 上下文中的项目:
For Each item In food
Dim weights = weight.Where(Function(x) x.FW_Food_ID = item.NDB_No)
... rest of code already posted above
model isn't null -- your test property is. model不为null - 您的测试属性是。 In the constructor of whatever item is, you need to "new" your collection. 在任何项目的构造函数中,您需要“新”您的集合。
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