Display DataTable in HTML Table in ASP.Net C# Webform

Question

I refer this website to try to write code - Display DataTable in HTML Table in ASP.Net C# Webform：http://www.aspsnippets.com/Articles/Display-DataTable-in-HTML-Table-in-ASPNet-using-C-and-VBNet.aspx

But can't show table information,show empty page. How can I fix this code？Thanks.

1.CS.aspx

 <%@ Page Language="C#" AutoEventWireup="true" CodeFile="CS.aspx.cs" Inherits="CS" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
    <style type="text/css">
`body { font-family: Arial;font-size: 10pt; }`

        table {
            border: 1px solid #ccc;
            border-collapse: collapse;
        }

            table th {
                background-color: #F7F7F7;
                color: #333;
                font-weight: bold;
            }

            table th, table td {
                padding: 5px;
                border-color: #ccc;
            }
    </style>
</head>
<body>
    <form id="form1" runat="server">
        <div style="margin-left: auto; margin-right: auto; text-align: center;">

            <asp:PlaceHolder ID="placeholder" runat="server" />

        </div>
    </form>
</body>
</html>

2.CS.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;
using System.Text;
using System.Configuration;




public partial class CS : System.Web.UI.Page
{

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            PlaceHolder placeholder = new PlaceHolder();

            //Populating a DataTable from database.
            DataTable dt = this.GetData();

            //Building an HTML string.
            StringBuilder html = new StringBuilder();

            //Table start.
            html.Append("<table border = '1'>");

            //Building the Header row.
            html.Append("<tr>");
            foreach (DataColumn column in dt.Columns)
            {
                html.Append("<th>");
                html.Append(column.ColumnName);
                html.Append("</th>");
            }
            html.Append("</tr>");

            //Building the Data rows.
            foreach (DataRow row in dt.Rows)
            {
                html.Append("<tr>");
                foreach (DataColumn column in dt.Columns)
                {
                    html.Append("<td>");
                    html.Append(row[column.ColumnName]);
                    html.Append("</td>");
                }
                html.Append("</tr>");
            }

            //Table end.
            html.Append("</table>");
            string strText = html.ToString();

            ////Append the HTML string to Placeholder.
            placeholder.Controls.Add(new Literal { Text = html.ToString() });

        }
    }

    private DataTable GetData()
    {
        string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT TOP 10 [a01],[a02],[a03] FROM [aaa].[dbo].[bbb]"))
            {
                using (SqlDataAdapter sda = new SqlDataAdapter())
                {
                    cmd.Connection = con;
                    sda.SelectCommand = cmd;
                    using (DataTable dt = new DataTable())
                    {
                        sda.Fill(dt);
                        return dt;
                    }
                }
            }
        }
    }
}

You are creating two different PlaceHolder in ASPX page and also in codebehind. Add controls to the placeholder created in aspx placeholder.Controls.Add(....) , here placeholder is your ID of PlaceHolder created in aspx page. — Rojalin Sahoo
– Rojalin Sahoo, Commented May 23, 2016 at 4:26

Alex W · Accepted Answer · 2016-05-23 04:23:35Z

If I had the points, I would have just made a comment but to fix your problem, all you need to do is comment out the following line:

PlaceHolder placeholder = new PlaceHolder();

The reason being is that, you have a PlaceHolder named placeholder on your markup, then create a completely new placeholder variable of Type PlaceHolder in the load code. Whilst they are named the same, the code considers them 2 completely different objects. See code below, also I borrowed someone else's code to create a datatable, since I don't have access to your db.

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        /*
        Commented out because doing it this way creates 
        2 PlaceHolder variables named placeholder, everything else is as needed
        */
        //PlaceHolder placeholder = new PlaceHolder();

        //Populating a DataTable from database.
        DataTable dt = this.GetData();
        //Building an HTML string.
        StringBuilder html = new StringBuilder();
        //Table start.
        html.Append("<table border = '1'>");
        //Building the Header row.
        html.Append("<tr>");
        foreach (DataColumn column in dt.Columns)
        {
            html.Append("<th>");
            html.Append(column.ColumnName);
            html.Append("</th>");
        }
        html.Append("</tr>");
        //Building the Data rows.
        foreach (DataRow row in dt.Rows)
        {
            html.Append("<tr>");
            foreach (DataColumn column in dt.Columns)
            {
                html.Append("<td>");
                html.Append(row[column.ColumnName]);
                html.Append("</td>");
            }
            html.Append("</tr>");
        }
        //Table end.
        html.Append("</table>");
        string strText = html.ToString();
        ////Append the HTML string to Placeholder.
        placeholder.Controls.Add(new Literal { Text = html.ToString() });
    }
}
private DataTable GetData()
{
    // Modified your method, since I don't have access to your db, so I created one manually
    // Here we create a DataTable with four columns.
    DataTable table = new DataTable();
    table.Columns.Add("Dosage", typeof(int));
    table.Columns.Add("Drug", typeof(string));
    table.Columns.Add("Patient", typeof(string));
    table.Columns.Add("Date", typeof(DateTime));

    // Here we add five DataRows.
    table.Rows.Add(25, "Indocin", "David", DateTime.Now);
    table.Rows.Add(50, "Enebrel", "Sam", DateTime.Now);
    table.Rows.Add(10, "Hydralazine", "Christoff", DateTime.Now);
    table.Rows.Add(21, "Combivent", "Janet", DateTime.Now);
    table.Rows.Add(100, "Dilantin", "Melanie", DateTime.Now);
    return table;
}

Denys Wessels · Accepted Answer · 2016-05-23 04:27:45Z

3

Comment out this line and it will work:

PlaceHolder placeholder = new PlaceHolder();

Just a thought.Rather than manually looping through the DataTable why not use the GridView control?

Code behind:

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = this.GetData();
        gridView.DataSource = dt;
        gridView.DataBind();
    }
}

ASPX Page:

<asp:GridView ID="gridView" runat="server"></asp:GridView>

answered May 23, 2016 at 4:27

Denys Wessels

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