上传文件的问题，Object reference not set to an instance of an object错误

[gzhantonio]

Upload按钮代码如下，每次执行到 FilenamePath = CType(Me.FindControl("FileUpload"), FileUpload).PostedFile 就出Object reference not set to an instance of an object错误，是FilenamePath没有实例化？该怎么改，谢谢
Protected Sub ButtonUpload1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles ButtonUpload1.Click
Dim FileUpload As New FileUpload '= Nothing
Dim FilenamePath As HttpPostedFile
Dim DisplayFilename As String

Try
'FileUpload.ID = "FileUpload" & i
FilenamePath = CType(Me.FindControl("FileUpload"), FileUpload).PostedFile
If FilenamePath.FileName <> "" Then
DisplayFilename = FilenamePath.FileName.Substring(FilenamePath.FileName.LastIndexOf("\") + 1)
'// Generate TimeStamp filename
Dim FileNameLength As String = InStr(1, StrReverse(FilenamePath.FileName), "\")
Dim ExtensionLength As String = InStr(1, StrReverse(FilenamePath.FileName), ".")
Dim Extension As String = Mid(FilenamePath.FileName, (Len(FilenamePath.FileName) - ExtensionLength) + 1)
Dim FileName As String = Left(DisplayFilename, (Len(DisplayFilename) - ExtensionLength))
Dim TimeStamp As String = Date.Now.ToString("ddHHmmss")
Dim StoredFilename As String = FileName + "_" + TimeStamp + Extension
'//
' set the upload directory
Dim UploadDirectory As String = ConfigurationManager.AppSettings("UploadDirectory")
'Me._InvoiceID = Request.QueryString("invoiceID")
'Me._CaseID = Session("CaseID")
Dim StoredFilePath As String = UploadDirectory & "\" & StoredFilename
FilenamePath.SaveAs(StoredFilePath)
InsertDocFile(Me._DocID, DisplayFilename, StoredFilename, StoredFilePath)
'AuditMan.log("upload", FilenamePath, UserID)
GridViewFiles.EditIndex = -1
'GridViewUploadFiles.Columns(5).Visible = True
'BindDataGrid()
End If
Catch ex As Exception
LabelMessage.Text = "Upload failed: " & ex.Message()
End Try
'BindGridView(True)
End Sub

[gzhantonio]

顶上去，等解答

[cpp2017]

Me.FindControl("FileUpload") 可能是空，检查一下。

[gzhantonio]

[Quote=引用 1 楼 cpp2017 的回复:]
Me.FindControl("FileUpload") 可能是空，检查一下。
[/Quote]
前台有ID为FileUpload的控件