Random taking of data from database based on conditions using .net c#

Question

i got code from internet it consist of a database table named as TblQuestions.created a Default.aspx page with a text box name as TxtRequiredRecords & button1. when value 2 enter in the textbox & click button1 it randomly generate 2 questions.if enter 5 it randomly produce 5 questions from table.i want to add another textbox2 for entering the option.my aim is that if i enter 2 in textbox1 and C in textbox2.it will generate 2 questions randomly from only option C questions.

where i modified in my code to obtain result?

my code Default.aspx :-

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!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>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
    <div>
        <asp:TextBox ID="TxtRequiredRecords" runat="server"></asp:TextBox>
        <asp:Button ID="BtnDisplayRecords" runat="server" OnClick="Button1_Click" Text="Display Records" />
        <br />
        <br />
        <asp:GridView ID="GvResults" runat="server">
        </asp:GridView>
    </div>
</form>
</body>
</html>

c# code:-

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.Collections;
public partial class _Default : System.Web.UI.Page
{
static int TotalRecords;
SqlConnection con;
SqlDataAdapter sqlda;
DataTable dt;
protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        string query = "SELECT COUNT(*) AS TotalRecords FROM TblQuestions";
        DataTable dt = GetRecords(query);
        TotalRecords = Convert.ToInt32(dt.Rows[0]["TotalRecords"]);
    }

}
protected void Button1_Click(object sender, EventArgs e)
{
    bool IsInt;
    int RequiredRecords;
    string CSVData, query;
    IsInt = Int32.TryParse(TxtRequiredRecords.Text, out RequiredRecords);
    if (IsInt)
    {
        if (TotalRecords >= RequiredRecords)
        {
            CSVData = GetRandomNumbersCSV(TotalRecords, RequiredRecords);
            query = "SELECT * FROM (SELECT ROW_NUMBER() OVER(ORDER BY QuestionID) AS RowID,* FROM TblQuestions)TempTable WHERE RowID IN(" + CSVData + ")";
            dt = GetRecords(query);
            GvResults.DataSource = dt;
            GvResults.DataBind();
        }
        else
        {
            Response.Write("Required Records must be greater than Requried Records.");
        }
    }
    else
    {
        Response.Write("Invalid Number");
    }
}

public ArrayList RandomNumbers(int max)
{
    ArrayList lstNumbers = new ArrayList();
    Random rndNumber = new Random();
    int number = rndNumber.Next(1, max + 1);
    lstNumbers.Add(number);
    int count = 0;
    do
    {
        number = rndNumber.Next(1, max + 1);
        if (!lstNumbers.Contains(number))
        {
            lstNumbers.Add(number);
        }
        count++;
    }
    while (count <= 10 * max);
    return lstNumbers;
}

public string GetRandomNumbersCSV(int max, int req)
{
    string CSV = "";
    ArrayList lstNumbers = RandomNumbers(max);
    for (int i = 0; i < req; i++)
        CSV += lstNumbers[i].ToString() + ",";
    CSV = CSV.Remove(CSV.Length - 1);
    return CSV;
}

public DataTable GetRecords(string Query)
{
    con = GetConnection();
    con.Open();
    sqlda = new SqlDataAdapter(Query, con);
    dt = new DataTable();
    sqlda.Fill(dt);
    con.Close();
    return dt;
}

public SqlConnection GetConnection()
{
    con = new SqlConnection(ConfigurationManager.ConnectionStrings["sqlcon"].ToString());
    return con;
}
}

Which .NET version? Any reason to use the outdated ArrayList ? — Henk Holterman
– Henk Holterman, Commented Mar 26, 2013 at 10:33

Henk Holterman · Accepted Answer · 2013-03-26 10:33:10Z

2

Normally, ID ranges can have gaps in them, your code would fail on that. And you are also struggling to avoid duplicates.

The correct way to do this

obtain a list of IDs from the table, you can add a condition for "Option C" only.
shuffle the IdList
take the first N elements

answered Mar 26, 2013 at 10:33

Henk Holterman

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