UserControl出現"並未將物件參考設定為物件的執行個體 "訊息

[Eric]

我寫了一個簡單的UserControl想要測試一下:
Public MustInherit Class WebUserControl
Inherits System.Web.UI.UserControl
Protected WithEvents DataGrid1 As System.Web.UI.WebControls.DataGrid

Property DataSource() As DataTable
Get
Return _dt
End Get
Set(ByVal Value As DataTable)
_dt = Value
End Set
End Property

Private _dt As New DataTable()

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Me.DataGrid1.DataSource = _dt
Me.DataBind()
End Sub
End Class

引用的程式如下:
Dim uc_WebUserControl As WebUserControl

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
myInit()
End Sub

Private Sub myInit()
Dim dt As New DataTable()
dt = getdatatable()
uc_WebUserControl = Me.FindControl("uc_WebUserControl1")
uc_WebUserControl.DataSource = dt
End Sub

結果出現下列錯誤:

並未將物件參考設定為物件的執行個體
描述: 在執行目前 Web 要求的過程中發生未處理的例外情形。請檢閱堆疊追蹤以取得錯誤的詳細資訊，以及在程式碼中產生的位置。

例外詳細資訊: System.NullReferenceException: 並未將物件參考設定為物件的執行個體

原始程式錯誤(行41):


行 39:
行 40: uc_WebUserControl = Me.FindControl("uc_WebUserControl1")
行 41: uc_WebUserControl.DataSource = dt
行 42:

原本以為dt有問題，
所以先把dt.rows.count秀出來看，
到這裡是沒問題的，
所以應該是UserControl的問題，
只是不曉得那裏出錯了，
請各位先進幫忙，
謝謝!!

[Eric]

不好意思，
測到頭昏，
是FindControl的ID給錯了...^^"

"Eric" 來函：

Post by Eric
Public MustInherit Class WebUserControl
Inherits System.Web.UI.UserControl
Protected WithEvents DataGrid1 As System.Web.UI.WebControls.DataGrid
Property DataSource() As DataTable
Get
Return _dt
End Get
Set(ByVal Value As DataTable)
_dt = Value
End Set
End Property
Private _dt As New DataTable()
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Me.DataGrid1.DataSource = _dt
Me.DataBind()
End Sub
End Class
Dim uc_WebUserControl As WebUserControl
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
myInit()
End Sub
Private Sub myInit()
Dim dt As New DataTable()
dt = getdatatable()
uc_WebUserControl = Me.FindControl("uc_WebUserControl1")
uc_WebUserControl.DataSource = dt
End Sub
並未將物件參考設定為物件的執行個體
描述: 在執行目前 Web 要求的過程中發生未處理的例外情形。請檢閱堆疊追蹤以取得錯誤的詳細資訊，以及在程式碼中產生的位置。
例外詳細資訊: System.NullReferenceException: 並未將物件參考設定為物件的執行個體
行 40: uc_WebUserControl = Me.FindControl("uc_WebUserControl1")
行 41: uc_WebUserControl.DataSource = dt
原本以為dt有問題，
所以先把dt.rows.count秀出來看，
到這裡是沒問題的，
所以應該是UserControl的問題，
只是不曉得那裏出錯了，
請各位先進幫忙，
謝謝!!

[Eric]

請問，
UserControl不能透過property傳DataTable嗎?
我試著把dt傳進去，
再get出來，
結果就變成空的了，
不曉得為什麼?
實在很困擾，
請各為先進幫忙，
感激不盡，
謝謝!!


"Eric" 來函：

Post by Eric
不好意思，
測到頭昏，
是FindControl的ID給錯了...^^"
"Eric" 來函：

Post by Eric
Public MustInherit Class WebUserControl
Inherits System.Web.UI.UserControl
Protected WithEvents DataGrid1 As System.Web.UI.WebControls.DataGrid
Property DataSource() As DataTable
Get
Return _dt
End Get
Set(ByVal Value As DataTable)
_dt = Value
End Set
End Property
Private _dt As New DataTable()
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Me.DataGrid1.DataSource = _dt
Me.DataBind()
End Sub
End Class
Dim uc_WebUserControl As WebUserControl
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
myInit()
End Sub
Private Sub myInit()
Dim dt As New DataTable()
dt = getdatatable()
uc_WebUserControl = Me.FindControl("uc_WebUserControl1")
uc_WebUserControl.DataSource = dt
End Sub
並未將物件參考設定為物件的執行個體
描述: 在執行目前 Web 要求的過程中發生未處理的例外情形。請檢閱堆疊追蹤以取得錯誤的詳細資訊，以及在程式碼中產生的位置。
例外詳細資訊: System.NullReferenceException: 並未將物件參考設定為物件的執行個體
行 40: uc_WebUserControl = Me.FindControl("uc_WebUserControl1")
行 41: uc_WebUserControl.DataSource = dt
原本以為dt有問題，
所以先把dt.rows.count秀出來看，
到這裡是沒問題的，
所以應該是UserControl的問題，
只是不曉得那裏出錯了，
請各位先進幫忙，
謝謝!!

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Post by Eric
Public MustInherit Class WebUserControl
Inherits System.Web.UI.UserControl
Protected WithEvents DataGrid1 As
System.Web.UI.WebControls.DataGrid
Property DataSource() As DataTable
Get
Return _dt
End Get
Set(ByVal Value As DataTable)
_dt = Value
End Set
End Property
Private _dt As New DataTable()
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Me.DataGrid1.DataSource = _dt
Me.DataBind()
End Sub
End Class
Dim uc_WebUserControl As WebUserControl
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
myInit()
End Sub
Private Sub myInit()
Dim dt As New DataTable()
dt = getdatatable()
uc_WebUserControl = Me.FindControl("uc_WebUserControl1")
uc_WebUserControl.DataSource = dt
End Sub
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[lyman]

Post by Eric
Public MustInherit Class WebUserControl
Inherits System.Web.UI.UserControl
Protected WithEvents DataGrid1 As System.Web.UI.WebControls.DataGrid
Property DataSource() As DataTable
Get
Return _dt
End Get
Set(ByVal Value As DataTable)
_dt = Value
End Set
End Property
Private _dt As New DataTable()
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Me.DataGrid1.DataSource = _dt
Me.DataBind()
End Sub
End Class
Dim uc_WebUserControl As WebUserControl
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
myInit()
End Sub
Private Sub myInit()
Dim dt As New DataTable()
dt = getdatatable()
uc_WebUserControl = Me.FindControl("uc_WebUserControl1")
uc_WebUserControl.DataSource = dt
End Sub
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