when i press the button the application gives me an error "index out of range" [closed] - asp.net

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Closed 10 years ago.
In this code I dynamically create checkboxes which I populate with data from my database.
My intention is when I press the btnProba button to show the text property only from the selected checkboxes. But it gives me an error in this row saying that index is out of range! I can't explain why.
lblProba.Text = myche[0];
public partial class FormEGN : System.Web.UI.Page
{
string mynewstring;
List<string> myche = new List<string>();
CheckBoxList mycheckbox = new CheckBoxList();
protected void Page_Load(object sender, EventArgs e)
{
mynewstring = (string)Session["id2"];
// lblProba.Text = mynewstring;
if(!IsPostBack)
{
ddlNumberTourists.Items.Add("1");
ddlNumberTourists.Items.Add("2");
ddlNumberTourists.Items.Add("3");
}
}
protected void ddlNumberTourists_SelectedIndexChanged(object sender, EventArgs e)
{
int numTourists = Convert.ToInt32(ddlNumberTourists.SelectedItem.Text);
for (int i = 0; i < numTourists; i++)
{
Label myLabel = new Label();
myLabel.ID = "lblAccomodation" + (i + 1).ToString();
myLabel.Text = "Настаняване Турист" + (i + 1).ToString();
Page.FindControl("form1").Controls.Add(myLabel);
DropDownList myDropDownList = new DropDownList();
myDropDownList.ID = "ddlTourist" + i.ToString();
Page.FindControl("form1").Controls.Add(myDropDownList);
Page.FindControl("form1").Controls.Add(new LiteralControl("<br />"));
string connectionString = "Server=localhost\\SQLEXPRESS;Database=EXCURSIONSDATABASE;Trusted_Connection=true";
string query =
"SELECT Extra_Charge_ID, Excursion_ID, Amout, Extra_Charge_Description FROM EXTRA_CHARGES WHERE Excursion_ID=" + mynewstring;
SqlConnection conn = new SqlConnection(connectionString);
SqlCommand cmd = new SqlCommand(query, conn);
try
{
conn.Open();
SqlDataReader rd = cmd.ExecuteReader();
int s = 0;
while (rd.Read())
{
// CheckBox myCheckbox = new CheckBox();
// myCheckbox.ID = "ckbExtraCharge" + i.ToString() + s.ToString();
// myCheckbox.Text = rd["Extra_Charge_Description"].ToString();
// Page.FindControl("form1").Controls.Add(myCheckbox);
// Page.FindControl("form1").Controls.Add(new LiteralControl("<br />"));
// s++;
mycheckbox.ID = "chkblextracharge" + i.ToString() + s.ToString();
mycheckbox.Items.Add(rd["Extra_Charge_Description"].ToString());
Page.FindControl("form1").Controls.Add(mycheckbox);
if (mycheckbox.Items[s].Selected == true)
{
myche.Add(mycheckbox.Items[s].Text);
}
s++;
}
}
catch (Exception ex)
{ }
}
}
protected void btnProba_Click(object sender, EventArgs e)
{
lblProba.Text = myche[0];
}
protected void btnReserve_Click(object sender, EventArgs e)
{
string num = Request.QueryString["ExcursionID"];
Response.Redirect(String.Format("ClintsInformation.aspx?Excursiondate_ID={0}",num));
}
}
}

Answer 1

The function ddlNumberTourists_SelectedIndexChanged is the one that set the myche when is find some selected, but the data is lost on the second call where is the
protected void btnProba_Click(object sender, EventArgs e)
{
// here is the issue
lblProba.Text = myche[0];
}
The two calls are happening on different post back.
You need to call the ddlNumberTourists_SelectedIndexChanged(object sender, EventArgs e) on button click and not on every change of the dropdownlist, eg I rename it to CheckWhatIsSelected() and here is the code:
protected void CheckWhatIsSelected()
{
int numTourists = Convert.ToInt32(ddlNumberTourists.SelectedItem.Text);
for (int i = 0; i < numTourists; i++)
{
Label myLabel = new Label();
myLabel.ID = "lblAccomodation" + (i + 1).ToString();
myLabel.Text = "??????????? ??????" + (i + 1).ToString();
Page.FindControl("form1").Controls.Add(myLabel);
DropDownList myDropDownList = new DropDownList();
myDropDownList.ID = "ddlTourist" + i.ToString();
Page.FindControl("form1").Controls.Add(myDropDownList);
Page.FindControl("form1").Controls.Add(new LiteralControl("<br />"));
string connectionString = "Server=localhost\\SQLEXPRESS;Database=EXCURSIONSDATABASE;Trusted_Connection=true";
string query =
"SELECT Extra_Charge_ID, Excursion_ID, Amout, Extra_Charge_Description FROM EXTRA_CHARGES WHERE Excursion_ID=" + mynewstring;
SqlConnection conn = new SqlConnection(connectionString);
SqlCommand cmd = new SqlCommand(query, conn);
try
{
conn.Open();
SqlDataReader rd = cmd.ExecuteReader();
int s = 0;
while (rd.Read())
{
// CheckBox myCheckbox = new CheckBox();
// myCheckbox.ID = "ckbExtraCharge" + i.ToString() + s.ToString();
// myCheckbox.Text = rd["Extra_Charge_Description"].ToString();
// Page.FindControl("form1").Controls.Add(myCheckbox);
// Page.FindControl("form1").Controls.Add(new LiteralControl("<br />"));
// s++;
mycheckbox.ID = "chkblextracharge" + i.ToString() + s.ToString();
mycheckbox.Items.Add(rd["Extra_Charge_Description"].ToString());
Page.FindControl("form1").Controls.Add(mycheckbox);
if (mycheckbox.Items[s].Selected == true)
{
myche.Add(mycheckbox.Items[s].Text);
}
s++;
}
}
catch (Exception ex)
{ }
}
}
protected void btnProba_Click(object sender, EventArgs e)
{
CheckWhatIsSelected();
if(myche.Count > 0)
lblProba.Text = myche[0];
else
lblProba.Text = "Non selected";
}
One other possible solution is to save the myche on viewstate.

Answer 2

Other solution using the ViewState. You use the ViewState to store your selection and you have it after the post back. Do not forget to clear your list on ddlNumberTourists_SelectedIndexChanged
List<string> myche
{
get
{
if (!(ViewState["cMyChe"] is List<string>))
{
// need to fix the memory and added to viewstate
ViewState["cMyChe"] = new List<string>();
}
return (List<string>)ViewState["cMyChe"];
}
}
protected void btnProba_Click(object sender, EventArgs e)
{
// double check if have something on the list
if(myche.Count > 0)
lblProba.Text = myche[0];
else
lblProba.Text = "Non selected";
}