Re: [ASP.NET] 指定的轉換無效
※ 引述《Lamfree (酷熱夏天)》之銘言：
感謝大大的回應，小弟這幾天也查有關findcontrol的用法
但卻不知該怎用ASP.NET寫，冏
因為查到資料大部分都是用JAVA或C#或VB.NET(跟ASP.NET還是有出入)
語法寫 所以很慚愧的又來問大大
可以簡述一下findcontrol跟control的轉換用法 及注意事項
感恩~~
還有回F大大 我想control(0)應該是textbox
看了回覆後參閱書本，並沒有講的很詳細，不過我前後看的很久
應該沒錯吧 希望您對此有所了解...可以幫小弟解惑
: 小弟不才最近剛接觸練習用ASP.NET的VB語法寫了一個新增、刪除、修改的退貨表單
: 並用SQLserver2000 當資料庫
: 不知為何在寫修改部分(照書上模式打)ꔩ[王有禮老師的透視ASP.NET]
: 在畫面修改完畢點選儲存時
: 卻出現"System.InvalidCastException指定的轉換無效"
: 上網找資料 仍然毫無頭緒
: 行 25: for i = 0 to e.Item.Cells.Count - 2
: 行 26:=>有問題的地方
: strText = CType(e.Item.Cells(i).Controls(0), TextBox).text
: 行 27: if strText <> "" then
: 行 28: params(j) = strText
: 堆疊追蹤:
: [InvalidCastException: 指定的轉換無效。]
: ASP.C_back_aspx.UpdateDataStore(DataGridCommandEventArgs e) in F:\Project_A\C_back.aspx:26
: ASP.C_back_aspx.b_form_Update(Object obj, DataGridCommandEventArgs e) in F:\Project_A\C_back.aspx:91
: System.Web.UI.WebControls.DataGrid.OnUpdateCommand(DataGridCommandEventArgs e) +109
: System.Web.UI.WebControls.DataGrid.OnBubbleEvent(Object source, EventArgs e) +507
: System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +26
: System.Web.UI.WebControls.DataGridItem.OnBubbleEvent(Object source, EventArgs e) +106
: System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +26
: System.Web.UI.WebControls.LinkButton.OnCommand(CommandEventArgs e) +121
: System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +115
: System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +18
: System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +138
: System.Web.UI.Page.ProcessRequestMain() +1292
: 這是全部程式碼
: <%@ Page Language = "VB" Debug="true"%>
: <%@ Import Namespace="System.Data" %>
: <%@ Import Namespace="System.Data.SQLClient" %>
: <html>
: <head>
: <title>客戶退貨</title>
: <script language="VB" runat="Server">
: Dim check_day As Date = Today
: Dim Conn As new SQLConnection("server=localhost;uid=sa;pwd=;database=ICS")
: '修改資料
: function UpdateDataStore( e as DataGridCommandEventArgs ) as Boolean
: dim i as integer
: dim j as integer = 0
: dim params(5) as string
: dim strText as string
: dim blnGo as boolean = true
: for i = 0 to e.Item.Cells.Count - 2
: strText = CType(e.Item.Cells(i).Controls(0), TextBox).text
: if strText <> "" then
: params(j) = strText
: j = j + 1
: else
: blnGo = false
: lblMessage.Text = lblMessage.Text & "欄位不可空白<p>"
: end if
: next
: if not blnGo then
: return false
: exit function
: end if
: dim strSQL as string = "Update 退貨單 set" & _
: "退貨單編號 = '" & params(0) & "'," & _
: "退貨商品編號 = '" & params(1) & "'," & _
: "退貨商品數量 = " & params(2) & "," & _
: "退貨商品售價 = " & params(3) & "," & _
: " where 退貨商品編號 ='" & CType(e.Item.Cells(2).Controls(0), TextBox).Text & "'"
: ExecuteStatement(strSQL)
: return blnGo
: end function
: sub Page_Load(obj as Object, e as EventArgs)
: if Not Page.IsPostBack then
: FillDataGrid2()
: end if
: end sub
: '顯示修改
: Sub FillDataGrid2(Optional EditIndex As integer = -1)
: dim objCmd2 as new SQLCommand("select * from 退貨單", Conn)
: dim objReader as SQLDataReader
: try
: objCmd2.Connection.Open()
: objReader = objCmd2.ExecuteReader()
: catch ex as Exception
: lblMessage.Text = "錯誤的資料庫運算"
: end try
: b_form.DataSource = objReader
: if not EditIndex.Equals(Nothing) then
: b_form.EditItemIndex = EditIndex
: end if
: b_form.DataBind()
: objReader.Close
: objCmd2.Connection.Close()
: End sub
: '修改資料
: sub b_form_Edit(obj as object, e as DataGridCommandEventArgs)
: FillDataGrid2(e.Item.ItemIndex)
: end sub
: '修改更新
: sub b_form_Update(obj as object, e as DataGridCommandEventArgs)
: if UpdateDataStore(E) then
: FillDataGrid2(-1)
: end if
: end sub
: '修改取消
: sub b_form_Cancel(obj as object, e as DataGridCommandEventArgs)
: FillDataGrid2(-1)
: end sub
: '新增
: Sub add_Click(Sender As object, e As EventArgs)
: if Page.IsValid then
: Dim strSQL as string = "Insert into 退貨單 (退貨單編號, 退貨日期, 退貨商品編號, 退貨商品數量, 退貨商品售價 )values " & _
: "('" & textbox0.text & "','" & check_day & "', '"& textbox1.text & "', '" & textbox2.text & "'," & _
: "'" & textbox3.text & "')"
: ExecuteStatement(strSQL)
: End If
: '顯示表格
: FillDataGrid()
: End Sub
: '清除
: Sub clear_Click(Sender As object, e As EventArgs)
: textbox0.text=" "
: textbox1.text=" "
: textbox2.text=" "
: textbox3.text=" "
: End Sub
: '刪除資料
: Sub b_form_delete(obj As Object, e As DataGridCommandEventArgs)
: Dim strSQL As string = "Delete From 退貨單 where 退貨單編號 = '" & e.Item.Cells(0).Text & "' "
: ExecuteStatement(strSQL)
: FillDataGrid()
: End sub
: '顯示退貨表
: Sub FillDataGrid(Optional EditIndex As integer = -1)
: Dim myCommand As new SQLDataAdapter("select * from 退貨單 where 退貨日期 = ('" & check_day & "') ", Conn)
: Dim dsC As DataSet = new DataSet()
: myCommand.Fill(dsC, "退貨單")
: b_form.DataSource = dsC.Tables("退貨單").DefaultView
: b_form.DataBind()
: End sub
: Function ExecuteStatement(strSQL)
: Dim objCmd as new SQLCommand(strSQL, Conn)
: try
: objCmd.Connection.Open()
: objCmd.ExecuteNonQuery()
: lblMessage.Text = "資料建檔完成!"
: catch ex as Exception
: lblMessage.Text = "建檔失敗!"
: End try
: objCmd.Connection.Close()
: End function
: </script>
: </head>
: <body>
: <h2>客戶退貨</h2><hr>
: <form id="Form1" runat="Server">
: <%
: Response.Write("退貨日期 : " & check_day)
: %><p></p>
: <p> 退貨單編號 :
: <asp:textbox id = "textbox0" Width="150px" runat="Server"/>
: <asp:RequiredFieldValidator ControlToValidate="textbox0"
: ErrorMessage="輸入退貨單編號"
: Type="string" runat="server"/>
: <p> 商品編號 :
: <asp:textbox id = "textbox1" Width="150px" runat="Server"/>
: <asp:RequiredFieldValidator ControlToValidate="textbox1"
: ErrorMessage="輸入商品編號"
: Type="string" runat="server"/>
: <p> 商品數量:
: <asp:textbox id = "textbox2" width="100px" runat="server"/>
: <asp:RequiredFieldValidator ControlToValidate="textbox2"
: ErrorMessage="輸入商品數量"
: Type="Integer" runat="server"/>
: <p> 商品售價 :
: <asp:textbox id = "textbox3" width="100px" runat="server"/>
: <asp:RequiredFieldValidator ControlToValidate="textbox3"
: ErrorMessage="輸入商品售價"
: Type="Integer" runat="server"/>
: <p> <asp:button id = "add" Text="新增" OnClick="add_Click" runat="server"/>
: <asp:button id = "clear" Text="清除" OnClick="clear_Click" runat="server"/>
: <asp:Label ID="lblMessage" runat="server" />
: <asp:DataGrid id="b_form" runat="Server" BorderColor="black" CellPadding="4" Font-Size="8pt"
: HeaderStyle-BackColor="#cccc99" ItemStyle-BackColor="#ffffff"
: AlternatingItemStyle-BackColor="#cccccc" AutoGenerateColumns="False"
: OnDeleteCommand="b_form_delete"
: OnEditCommand="b_form_Edit" OnCancelCommand="b_form_Cancel" OnUpdateCommand="b_form_Update">
: <Columns>
: <asp:BoundColumn HeaderText="退貨單編號" DataField="退貨單編號"/>
: <asp:BoundColumn HeaderText="退貨日期" DataField="退貨日期"/>
: <asp:BoundColumn HeaderText="商品編號" DataField="退貨商品編號"/>
: <asp:BoundColumn HeaderText="商品數量" DataField="退貨商品數量"/>
: <asp:BoundColumn HeaderText="商品售價" DataField="退貨商品售價"/>
: <asp:ButtonColumn ButtonType="PushButton" HeaderText="刪除" Text="刪除" CommandName="delete"/>
: <asp:EditCommandColumn EditText="修改" CancelText="還原"
: UpdateText="儲存" HeaderText="編輯" ItemStyle-Wrap="False"/>
: </Columns>
: </asp:DataGrid>
: </form></body></html>
: 希望板上大大能幫小弟解惑
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