Passing values to next page C# ASP.NET

Question

In my code, after i choose the value in the drop down list and hit enter it send the first value of the drop down list instead

May I know what are the possible causes?

Below is my code:

protected void Button1_Click(object sender, EventArgs e)
{
    if (DayBox.Text != "" && MonthBox.Text != "" && YearBox.Text != "")
    {
        string date;
        int container = Convert.ToInt32(DayBox.Text);

        if (container < 10)
        {
            date = String.Format("0{0}/{1}/{2}", DayBox.Text, MonthBox.Text, YearBox.Text);
        }
        else
        {
            date = String.Format("{0}/{1}/{2}", DayBox.Text, MonthBox.Text, YearBox.Text);
        }


        Session["DATE"] = date;
        Session["IPADDRESS"] = IPDropDownList.Text;

        Response.Redirect("IPAddressDay.aspx");
    }
}

Code for the dropdown box:

//this if statment is for gettting the ip address for that Month;
if (DayBox.Text == "" && MonthBox.Text != "" && YearBox.Text != "")
{
    IPDropDownList.Items.Clear();

    string date;
    date = String.Format("{0}/{1}",MonthBox.Text, YearBox.Text);

    sqlStatment = String.Format("SELECT IPAddress FROM IPActivity WHERE AccessDate LIKE '%{0}' GROUP BY IPAddress;", date);

    MyDataSet = RetriveDataBase(connection, sqlStatment, tableName);//method written by me

    dra = MyDataSet.Tables[tableName].Rows;

    foreach (DataRow dr in dra)
    {
        IPDropDownList.Items.Add(dr[0].ToString());
    }
     //this is to close the if statment for gettting the ip address for that Month;
}

Description: It will not read the value I choose, but take the first value instead and send to next page

Answer 1

Assuming you fill your DropDownList at your Page_Load event, you need to use IsPostBack . Everytime you hit the button Page_Load event is fired before your Button1_Click event. Therefore, at your Button1_Click you get the first value in dropdownlist always. Correct code should be,

if (!IsPostBack && DayBox.Text == "" && MonthBox.Text != "" && YearBox.Text != "")
{
    IPDropDownList.Items.Clear();

    string date = String.Format("{0}/{1}",MonthBox.Text, YearBox.Text);

    sqlStatment = String.Format("SELECT IPAddress FROM IPActivity WHERE AccessDate LIKE '%{0}' GROUP BY IPAddress;", date);

    MyDataSet = RetriveDataBase(connection, sqlStatment, tableName);

    foreach (DataRow dr in MyDataSet.Tables[tableName].Rows;)
    {
        IPDropDownList.Items.Add(dr[0].ToString());
    }   
}

Answer 2

Try this:

Session["IPADDRESS"] = IPDropDownList.SelectedValue;

then, to set the value:

IPDropDownList.SelectedValue = Session["IPADDRESS"] != null ? Session["IPADDRESS"].ToString() : "" ;

And don't reset your dropdownlist if you're posting back.

if(!IsPostBack)
{
   //Code to set dropdownlist values here
}

Answer 3

You need:

Session["IPADDRESS"] = IPDropDownList.SelectedValue;

As select boxes have a value property which gets the value of the option which can differ from the text displayed.