Fileupload control in master page

hi,
i use fileupload control for upload image in my page.so below is my code to check file upload or not.
 Dim fileUpload1 As FileUpload = CType(Me.FindControl("fileUpload1 "), FileUpload)
            'Make sure a file has been successfully uploaded
            If fileUpload1.PostedFile Is Nothing OrElse String.IsNullOrEmpty(fileUpload1.PostedFile.FileName) OrElse fileUpload1.PostedFile.InputStream Is Nothing Then
                Label1.Text = "Please Upload Valid picture file"
                Exit Sub
            End If
 
but problem is when i debug it in f ...