Question

我试图编写一些显示面板网格（grid []）的代码到更大的面板（gridHolder）上。到目前为止，这是我的代码：

public void setupPanels(int x, int y)
    {

        grid = new Panel[y, x];
        this.Controls.Add(gridHolder);
        gridHolder.Show();
        gridHolder.Location = new Point(0 , 0);
        gridHolder.Size = new Size(x * PANEL_SIZE, y * PANEL_SIZE);

        for (int i = 0; i < grid.GetLength(0); i++)
        {

            for (int j = 0; j < grid.GetLength(1); j++)
            {

                gridHolder.Controls.Add(grid[i, j]);
                grid[i, j].Location = new Point(i * PANEL_SIZE, j * PANEL_SIZE);
                gridHolder.Size = new Size(PANEL_SIZE, PANEL_SIZE);

            }

        }



    }

当我尝试运行该程序时，我收到一个调试错误，说＆＃34; NullReferenceException未处理＆＃34;。我该如何修复我的代码？

Answer 1

很远的猜测..但试试这个：在你的Page_Load方法中更改内部代码，以便调用setupPanels方法的行不会在每个条目上调用它，而只在非回发调用中调用它，应该看起来像这样：

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
        setupPanels(...)
}

以下是一个完整的例子：

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication3.WebForm1" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:panel ID="gridHolder" runat="server"/>
    </form>
</body>
</html>



public partial class WebForm1 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
            SetupPanels(gridHolder, 40, 40, 6, 6);
    }

    private void SetupPanels(Panel panelsHolder, int widthPerPanel, int heightPerPanel, int panelsCountX, int panelsCountY)
    {
        panelsHolder.Style.Add("position","absolute");
        panelsHolder.Width = widthPerPanel*panelsCountX;
        panelsHolder.Height = heightPerPanel*panelsCountY;
        for (int y = 0; y < panelsCountY; y++)
        {
            for (int x = 0; x < panelsCountX; x++)
            {
                var gridPanel = new Panel
                {
                    Width = widthPerPanel,
                    Height = heightPerPanel,
                    BackColor = Color.SandyBrown,
                    BorderColor = Color.Black,
                    BorderWidth = 5,
                };
                gridPanel.Style.Add("position", "absolute");
                gridPanel.Style.Add("top", (x*widthPerPanel) + "px");
                gridPanel.Style.Add("left", (y*heightPerPanel) + "px");
                panelsHolder.Controls.Add(gridPanel);
            }
        }
    }

}

C＃：制作一个二维的面板阵列

1 个答案: