我需要驗證在asp.net中的查詢字符串

Question

Dim objItems As clsItems 

'Loads the pages with the Gridview and Infomation pretaining to the Item selected 
Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load 

    Dim qryItemNum As String = Request.QueryString("qryItemNum") 

    'Populates Gridview 
    If Not Page.IsPostBack Then 
     gvwCategorySelect.DataSource = clsCategory.GetList 
     gvwCategorySelect.DataBind() 

     'imgbtnPrev.Visible = False 

     'If Not String.IsNullOrEmpty(qryItemNum) Then 
     ' Dim ItemNum As Int32 
     ' If Int32.TryParse(test, ItemNum) Then 
     '  imgbtnPrev.Visible = (-1 < ItemNum) 
     ' End If 
     'End If 
    End If 


    objItems = New clsItems(qryItemNum) 

    'Set up the from labels 
    lblTitle.Text = objItems.Title 
    lblPrice.Text = objItems.Price.ToString("C") 
    lblDescription.Text = objItems.Description 
    ImgItem.ImageUrl = "~/images/ItemImages/Item" & objItems.ItemNum & ".jpg" 



End Sub 

'Returns to pervious item 
Protected Sub imgbtnPrev_Click(sender As Object, e As System.Web.UI.ImageClickEventArgs) Handles imgbtnPrev.Click 

    Response.Redirect("~/ItemInfo.aspx?qryItemNum=" & objItems.ItemNum - 1) 

End Sub 

'Next item 
Protected Sub imgbtnNext_Click(sender As Object, e As System.Web.UI.ImageClickEventArgs) Handles imgbtnNext.Click 


    Response.Redirect("~/ItemInfo.aspx?qryItemNum=" & objItems.ItemNum + 1) 

End Sub 

在上面的代碼中有2個圖像按鈕，它們在不同的ItemNum之間移動。我試着從點擊後退按鈕停止用戶，通過移除imgbtnPrev按鈕時，在1

錯誤信息的查詢字符串說，有在位置沒有行0

dataRowObject = DBMethods.CreateTable(sqlString, sqlArg).Rows(0) 

^這裏是哪裏是其突出顯示。

Answer 1

試試這個

int number; 
    if(Request.QueryString["qryItemNum"]!= null) 
    { 
    bool isNumeric = int.TryParse(Request.QueryString["qryItemNum"].ToString(), out number); 
     if(isNumeric == true) 
     { 
     if(Convert.ToInt(Request.QueryString["qryItemNum"])<=1) 
     { 
      imgbtnPrev = false; 
     } 
     } 
    } 

編輯： 我轉換，爲VB.NET

Dim number As Integer 
    If Request.QueryString("qryItemNum") IsNot Nothing Then 
Dim isNumeric As Boolean = Integer.TryParse(Request.QueryString("qryItemNum").ToString(), number) 
    If isNumeric = True Then 
    If Convert.ToInt(Request.QueryString("qryItemNum")) <= 1 Then 
     imgbtnPrev = False 
    End If 
    End If 
    End If 

Answer 2

我覺得這是VB是怎麼做的：

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
    If Not Page.IsPostBack Then 
     imgbtnPrev = False 
     Dim qryItemNum As String = Request.QueryString("qryItemNum") 
     If Not String.IsNullOrEmpty(qryItemNum) Then 
      Dim ItemNum As Int32 
      If Int32.TryParse(qryItemNum, ItemNum) Then 
      imgbtnPrev = (-1 < ItemNum) 
      End If 
     End If 
    End If 
End Sub 

這是假設，當然，imgbtnPrev是有些定義的在你的代碼或你的ASPX頁面中。

編輯：從您的評論imgbtnPrev.Visible = False到你原來的問題之一，看來imgbtnPrev是表單上的一個按鈕。如果是這樣的話，你會寫是這樣的：

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
    If Not Page.IsPostBack Then 
     imgbtnPrev.Visible = False 
     Dim qryItemNum As String = Request.QueryString("qryItemNum") 
     If Not String.IsNullOrEmpty(qryItemNum) Then 
      Dim ItemNum As Int32 
      If Int32.TryParse(qryItemNum, ItemNum) Then 
      imgbtnPrev.Visible = (-1 < ItemNum) 
      End If 
     End If 
    End If 
End Sub 

EDIT2：該版本採用Try...Catch，看看有什麼錯誤是：

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
    If Not Page.IsPostBack Then 
     imgbtnPrev.Visible = False 
     Try 
      Dim qryItemNum As String = Request.QueryString("qryItemNum") 
      If Not String.IsNullOrEmpty(qryItemNum) Then 
      Dim ItemNum As Int32 
      If Int32.TryParse(qryItemNum, ItemNum) Then 
       imgbtnPrev.Visible = (-1 < ItemNum) 
      End If 
      End If 
     Catch err As Exception 
      Response.Write(err.Message) 
     End Try 
    End If 
End Sub 

希望它能幫助！