Question

如何从应用代码中的类文件访问控件？

标记：

<%@ Page Language="vb" AutoEventWireup="false" Inherits="shoppingCart1.ShoppingPage" CodeFile="ShoppingPage.aspx.vb" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
    <HEAD>
        <title>ShoppingPage</title>
        <meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR">
        <meta content="Visual Basic .NET 7.1" name="CODE_LANGUAGE">
        <meta content="JavaScript" name="vs_defaultClientScript">
        <meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
    </HEAD>
    <body>
        <form id="Form1" method="post" runat="server" name="Form1">
            <TABLE id="tblShopping" style="FONT-SIZE:10pt;FONT-FAMILY:verdana" borderColor="black"
                width="100%" cellSpacing="0" cellPadding="0" border="1" runat="server">
                <tr style="FONT-SIZE:10pt;FONT-FAMILY:verdana;color:white;background-color:#336699;font-weight:bold;">
                    <td colspan="4">PRODUCT LIST</td>
                </tr>
                <tr>
                    ***<td id="cellshoping" runat="server" colspan="4" width="100%"></td>***
                </tr>
                <tr>
                </tr>
            </TABLE>
        </form>
    </body>
</HTML>

ShoppingCart.vb在App_Code文件夹

Imports Microsoft.VisualBasic
Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration

Public Class ShoppingCart
    Public Sub bindData()
        Dim con As New SqlConnection("Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True")
        Dim objDA As SqlDataAdapter
        Dim myRow As SqlDataReader
        Dim comd As New SqlCommand("SELECT * FROM products", con)
        con.Open()
        myRow = comd.ExecuteReader()
        Dim strRowGen As String = ""
        While myRow.Read()
            strRowGen = strRowGen & "<TR>"
            strRowGen = strRowGen & "<TD>" & myRow.GetValue(0) & "</TD>"
            strRowGen = strRowGen & "<TD>" & myRow.GetValue(1) & "</TD>"
            strRowGen = strRowGen & "<TD>" & myRow.GetValue(2) & "</TD>"
            strRowGen = strRowGen & "<TD><a href='#' onclick=""javascript:document.Form1.action='ShoppingPage.aspx?Actn=Add&itemId=" & myRow.GetValue(0) & "';document.Form1.submit();"">Add To Cart</TD>"
            strRowGen = strRowGen & "</TR>"
            **cellshoping**.InnerHtml = strRowGen
        End While
    End Sub
End Class

我在cellshoping.InnerHtml 时遇到错误“未声明” ...如何从应用程序代码中的类文件访问用户控件？

后面添加ASPX代码

Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration


Namespace shoppingCart1

Partial Class ShoppingPage
    Inherits System.Web.UI.Page
#Region " Web Form Designer Generated Code "

    'This call is required by the Web Form Designer.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()

End Sub
Protected WithEvents Label1 As System.Web.UI.WebControls.Label
Protected WithEvents Label2 As System.Web.UI.WebControls.Label
Protected WithEvents Label3 As System.Web.UI.WebControls.Label
Protected WithEvents txtNK As System.Web.UI.WebControls.TextBox
Protected WithEvents txtCF As System.Web.UI.WebControls.TextBox
Protected WithEvents txtHA As System.Web.UI.WebControls.TextBox
Protected WithEvents dtGrdProducts As System.Web.UI.WebControls.DataGrid


Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
    'CODEGEN: This method call is required by the Web Form Designer
    'Do not modify it using the code editor.
    InitializeComponent()
End Sub

#End Region
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    'Put user code to initialize the page here
    'Load data by calling function bindData()
            Dim sCart = New ShoppingCart
            If Not Page.IsPostBack Then

                cellshoping.InnerHtml = sCart.bindData()
            End If
    Dim strQty As Integer
    Dim proId As String
    Dim delId As String

    delId = Request.QueryString("delItemId")
    proId = Request.QueryString("itemId")
        '------ Following portion act as controller where code is written as
        '------ per the action from the request of the pages like Add To Cart,
        '------ Update Cart & Delete Cart
    strQty = 1
    If Request.QueryString("Actn") <> "" Then
        If Request.QueryString("Actn").Equals("Add") Then
                    If Request.QueryString("itemId") <> "" Then
                        AddToSession(proId, strQty)
                        Response.Redirect("./ShoppingCart.aspx")
                    End If
        ElseIf Request.QueryString("Actn").Equals("Del") Then
            If Request.QueryString("delItemId") <> "" Then
                Session.Remove(delId)
                Response.Redirect("./ShoppingCart.aspx")
            End If
        ElseIf Request.QueryString("Actn").Equals("Update") Then
            If Request.QueryString("itemUpId") <> "" And Request.QueryString("quantity") <> "" Then
                If IsNumeric(Request.QueryString("itemUpId")) Then
                    updateCart(Request.QueryString("itemUpId"), Request.QueryString("quantity"))
                    Response.Redirect("./ShoppingCart.aspx")
                Else
                    Response.Redirect("./ShoppingCart.aspx")
                End If
            End If
        End If
    End If
End Sub
Private Sub AddToSession(ByVal strProduct As String, ByVal intQty As Integer)
    If Not Session(strProduct) Is Nothing Then
        Session.Add(strProduct, CInt(Session(strProduct)) + intQty)
    Else
        Session.Add(strProduct, intQty)
    End If
End Sub
Private Sub updateCart(ByVal strProduct As String, ByVal qty As Integer)
    If Not Session(strProduct) Is Nothing Then
        Session.Add(strProduct, CInt(qty))
    End If
End Sub

End Class
End Namespace

Answer 1

假设在页面的代码隐藏中的某处引用了ShoppingCart类，并且从该代码调用了BindData（）方法，那么您有几个选择：

1）将对页面的引用传递给购物车的绑定数据方法。

2）将数据从BindData（）方法返回到页面，以便它可以适当地更新页面中的数据。

3）您可以访问HttpContext.Current.Handler并将其强制转换为您的页面实例。

我的建议，特别是如果你想在其他页面中使用该类，是要么创建一个接口，该接口具有可用于更新数据和使用选项1或3的方法，或者实现选项2。

以下是如何更改代码以实现和界面的示例。

界面：

Public Interface IShoppingCartPage
    Sub UpdateData(sCartContents As String)
End Interface

页面codebeghind（部分）：

Public Class ShoppingPage
    Implements IShoppingCartPage

    Public Sub UpdateData(sCartContents As String) Implements IShoppingCartPage.UpdateData
        cellshopping.innerHtml = sCartContents
    End Sub
End Class

最后，修改后的购物车类（注意使用stringbuilder类，这将比问题中的字符串concat更有效）：

Public Class ShoppingCart
    Public Sub bindData(oPage As IShoppingCartPage)
        Using con As New SqlConnection("Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True")
            Using comd As New SqlCommand("SELECT * FROM products", con)
                con.Open()
                Using oReader As SqlDataReader = comd.ExecuteReader()
                    Dim sbHTML As New System.Text.StringBuilder(5000)
                    While oReader.Read()
                        sbHTML.Append("<TR>")
                        sbHTML.Append("<TD>").Append(oReader.GetValue(0)).Append("</TD>")
                        sbHTML.Append("<TD>").Append(oReader.GetValue(1)).Append("</TD>")
                        sbHTML.Append("<TD>").Append(oReader.GetValue(2)).Append("</TD>")
                        sbHTML.Append("<TD><a href='#' onclick=""javascript:document.Form1.action='ShoppingPage.aspx?Actn=Add&itemId=").Append(oReader.GetValue(0)).Append("';document.Form1.submit();"">Add To Cart</TD>")
                        sbHTML.Append("</TR>")
                    End While

                    oPage.UpdateData(sbHTML.ToString())
                End Using
            End Using
            con.Close()
        End Using
    End Sub
End Class

Answer 2

为什么不让你的方法返回一个字符串？

Public Function bindData() as String
    Dim con As New SqlConnection("Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True")
    Dim objDA As SqlDataAdapter
    Dim myRow As SqlDataReader
    Dim comd As New SqlCommand("SELECT * FROM products", con)
    con.Open()
    myRow = comd.ExecuteReader()
    Dim strRowGen As String = ""
    While myRow.Read()
        strRowGen = strRowGen & "<TR>"
        strRowGen = strRowGen & "<TD>" & myRow.GetValue(0) & "</TD>"
        strRowGen = strRowGen & "<TD>" & myRow.GetValue(1) & "</TD>"
        strRowGen = strRowGen & "<TD>" & myRow.GetValue(2) & "</TD>"
        strRowGen = strRowGen & "<TD><a href='#' onclick=""javascript:document.Form1.action='ShoppingPage.aspx?Actn=Add&itemId=" & myRow.GetValue(0) & "';document.Form1.submit();"">Add To Cart</TD>"
        strRowGen = strRowGen & "</TR>"            
    End While
    Return strRowGen

End Sub

然后你可以从你的页面中调用它

Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
   'Set innerHtml here
   'cellshoping.InnerHtml = ShoppingCart.bindData()
End Sub

如何从应用程序代码中的类文件访问控件

2 个答案: