-1
在我的程序中，我有幾個加載動態字段的單選按鈕。當我選擇第一個單選按鈕時，所有的字段都被加載。但是，當我選擇另一個單選按鈕時，字段不會出現，並且出現錯誤「未將對象引用設置爲對象的實例」。我試圖清除佔位符，但它沒有奏效。我認爲這個問題與單選按鈕有關，因爲當我發表評論時，一切都很完美。但遺憾的是我需要這些按鈕。'對象引用未設置爲對象的實例'動態控件
我知道這個問題已經被問了很多次，我也試圖解決我的問題與不同的主題，但我不知道現在該做什麼...
下面是代碼
Protected Sub ServiceTypeList_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ServiceTypeList.SelectedIndexChanged
Dim tmpservicetype As New servicetype(ServiceTypeList.SelectedItem.Value)
Dim tmpFieldName As String
Try
Dim cmdstr As String
PlaceHolder1.Controls.Clear()
lblText.Controls.Clear()
cmdstr = "SELECT servicetype, FieldName, FieldType, FieldLength, FieldLabelEmail, ToolboxType, Height, Width, TabIndex FROM tblDynamicControl WHERE (servicetype = '" & tmpservicetype.servicetype & "') ORDER BY TabIndex"
Dim cmd As New SqlCommand(cmdstr)
Dim dt As DataTable = EMGEHelpdesk.SharedCode.ExecuteCMD(cmd).Tables(0)
For i = 0 To dt.Rows.Count - 1
Dim dr As DataRow = dt.Rows(i)
tmpFieldName = SetDataVar(dr, "FieldName")
Dim NewField As New DynamicControl(tmpservicetype.servicetype, tmpFieldName, "GB")
Select Case NewField.ToolboxType
Case "TextBox"
Dim DXTextbox As ASPxTextBox
Dim DXLabel As ASPxLabel
DXTextbox = New ASPxTextBox
DXTextbox.ID = NewField.FieldName & "_field"
DXTextbox.Width = NewField.Width
DXTextbox.Height = NewField.Height
DXTextbox.TabIndex = NewField.TabIndex
DXTextbox.CssClass = "Field"
PlaceHolder1.Controls.Add(DXTextbox) --> **The error appears here**
DXLabel = New ASPxLabel
DXLabel.ID = NewField.FieldName.ToString & "_lbl"
DXLabel.Text = NewField.lblText
DXLabel.CssClass = "TextBox"
lblText.Controls.Add(DXLabel)
DXTextbox.Controls.Add(DXLabel)
Case "RadioButton"
Dim BXRadiobutton As ASPxRadioButtonList
Dim BXLabel As ASPxLabel
BXRadiobutton = New ASPxRadioButtonList
BXRadiobutton.DataSource = Split(NewField.FieldName)
BXRadiobutton.DataBind()
BXRadiobutton.RepeatDirection = RepeatDirection.Horizontal
BXRadiobutton.ID = NewField.FieldName & "_field"
BXRadiobutton.TabIndex = NewField.TabIndex
BXRadiobutton.CssClass = "Button"
PlaceHolder1.Controls.Add(BXRadiobutton)
BXLabel = New ASPxLabel
BXLabel.ID = NewField.FieldName.ToString & "_lbl"
BXLabel.Text = NewField.lblText
BXLabel.CssClass = "RadioButton"
lblText.Controls.Add(BXLabel)
BXRadiobutton.Controls.Add(BXLabel)
Case "MemoBox"
Dim MXMemobox As ASPxMemo
Dim MXLabel As ASPxLabel
MXMemobox = New ASPxMemo
MXMemobox.ID = NewField.FieldName & "_field"
MXMemobox.Width = NewField.Width
MXMemobox.Height = NewField.Height
MXMemobox.TabIndex = NewField.TabIndex
MXMemobox.CssClass = "Field"
PlaceHolder1.Controls.Add(MXMemobox)
MXLabel = New ASPxLabel
MXLabel.ID = NewField.FieldName.ToString & "_lbl"
MXLabel.Text = NewField.lblText
MXLabel.CssClass = "MemoBox"
lblText.Controls.Add(MXLabel)
MXMemobox.Controls.Add(MXLabel)
End Select
Next
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
末級
而該線路上的，什麼是'Nothing' - 'PlaceHolder1'，'PlaceHolder1.Controls'或'DXTextbox'？ – GSerg
PlaceHolder1是PlaceHolders名稱，Placeholder1.Controls.Add允許我在佔位符上添加控件，而DXTextbox是文本框的名稱。基本上，這一行允許我添加文本框（爲每個文本框添加一個新的控件）。你在哪裏看到「沒有」？ – georges619
您可以告訴我們PlaceHolder1的模型嗎？當您嘗試向其添加對象時發生錯誤，但不能將對象添加到** Nothing **。 – PSo