为什么我的表在ASP.NET中没有内容？

Question

我在类GetData.cs中构建了一个表

public Table  BuildTable()
{
    Table tButtons = new Table();
    TableRow tRow = new TableRow();
    TableCell tCell = new TableCell();
    long lColumn = 0;
    long lPreviousColumn = 0;
    long lRow = 0;
    long lPreviousRow = 0;
    long lLanguage = 0;
    long lPreviousLanguage=0;
    OpenConnection();
    ButtonData();
    Int32 lRowOrd = aReader.GetOrdinal("RowNumber");
    Int32 lColOrd = aReader.GetOrdinal("ColumnNumber");
    Int32 lLangOrd = aReader.GetOrdinal("Language");
    Int32 lLabelOrd = aReader.GetOrdinal("Label");

    while (aReader.Read())
    {

        lRow = IsDbNull(aReader,lRowOrd);//first get our column number
        lColumn = IsDbNull(aReader,lColOrd);//first get our column number
        lLanguage = IsDbNull(aReader,lLangOrd);//first get our column number
        if (lPreviousRow != lRow)//we have a new row 
        {
            if (lPreviousRow != 0)//then we are working on one and need to save it before moving on
            {
                tButtons.Rows.Add(tRow);//add the new row to the table
            }
            lPreviousRow = lRow;//remember the value for next time
            tRow = new TableRow();
            tRow.Visible = true;
            //*******put the category titles in here somewhere
        }
        if (lPreviousColumn != lColumn)//we have a new column
        {
            if (lPreviousColumn != 0)//then we are working on one and need to save it before moving on
            {
                tRow.Cells.Add(tCell);//add the new cell to the row
            }
            lPreviousColumn = lColumn;//remember the value for next time
            //*******add the cell colors
            if (lPreviousLanguage != lLanguage)//we have a new column
            {
                lPreviousLanguage = lLanguage;//remember the value for next time
                tCell.Text = IsDbNull(aReader,lLabelOrd,"");
                //*******add the languages to properties
            }
            tCell = new TableCell();
            tCell.Visible=true;
        }
    }
    CloseConnection();
    tButtons.Visible=true;
    return tButtons;
}

在我的Default.aspx.cs页面中

GetData Buttons = new GetData();//create a reference to the class
ButtonTable = Buttons.BuildTable();
OutPut.Text = ButtonTable.Rows.Count.ToString();

在Default.aspx中

<asp:Table runat="server" ID="ButtonTable" />   
<asp:Label runat="server" ID="OutPut" />

输出显示4行,但表为空.

<table id="ButtonTable" border="0"></table>

我究竟做错了什么？

Answer 1

我错过了什么？

显然,很多.在标记中,您已声明了System.Web.UI.WebControls.Table的实例.在您的Page类的实例中,它将具有变量名称"ButtonTable".它也将自动添加到Page.Controls集合中.当要渲染页面时,将循环迭代并呈现Controls集合.

在default.aspx.cs代码中,您只是将ButtonTable引用指向另一个Table控件 - 但您不会影响Page.Controls集合.当渲染时间到来时,它将在标记中定义的(空白)表格将被渲染 - 而不是您的BuildTable调用的结果.

所有这一切都是相当漫长的"你做错了".为什么你希望你的表在一个单独的类中构建代码的答案将会对"正确的方法"有所了解.但是 - 我的意思是没有冒犯 - 我认为你需要先学习ASP.NET背后的基础知识,然后再继续学习.

话虽这么说,最直接的修复(但可能不是你真正想要的)是将表添加到Controls集合,以便它被渲染:

GetData Buttons = new GetData();//create a reference to the class
ButtonTable = Buttons.BuildTable();
this.Controls.Add(ButtonTable);
OutPut.Text = ButtonTable.Rows.Count.ToString();

请注意,它会单独渲染从您的标记定义ButtonTable,因此将被放置后输出的标签.那是因为它是在Output标签之后添加的.