Without Last the values of Controls in aspx page when its redirected from Paypal site

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C#

C#4.0

ASP.NET4

I am creating a web directory site.. user need to pay for listing urls..I have using paypal for transferred the amount..when its success then the page can be redirected to the submitted page..But i have lost all values in that page...I don't want to lost values of a controls and after amount transferred then only i need to store that all details into db...How can i do that?

Aspx.cs:

protected void SubmitBtn_Click(object sender, EventArgs e)
{
if (this.txtimgcode.Text == this.Session["CaptchaImageText"].ToString())
{
string title = TitleTxtbx.Text;
string url = urlTxtbx.Text;
string desc = DescriptionTxtbx.InnerText;
string name = nameTxtbx.Text;
string mail = mailTxtbx.Text;
int catid = Convert.ToInt32(CategoryDDL.SelectedValue);
int subid= Convert.ToInt32(SubCategoryDDL.SelectedValue);
string paidtype=PaidTypeRBL.SelectedValue;
string keywords = keywordTxtbx.Text;

DataTable dtlist = new DataTable("Listingtypetb");
DataColumn dc_url = new DataColumn("URL", typeof(string));
DataColumn dc_title = new DataColumn("Title", typeof(string));

dtlist.Columns.Add(dc_url);
dtlist.Columns.Add(dc_title);


if (paidtype == "$2.00")
{
string secondtitle = SecondTitleTxtbx.Text;
string secondurl = SecondurlTxtbx.Text;
DataRow drlist = dtlist.NewRow();

if ((secondtitle != "" && secondtitle != null) && (secondurl != "" && secondurl != null))
{

drlist["URL"] = secondurl;
drlist["Title"] = secondtitle;
dtlist.Rows.Add(drlist);
}

}
else
{
if (paidtype == "$5.00")
{
string twotitle = TwotitleTxtbx.Text;
string twourl = TwourlTxtbx.Text;
DataRow drlist = dtlist.NewRow();

if ((twotitle != "" && twotitle != null) && (twourl != "" && twourl != null))
{

drlist["URL"] = twourl;
drlist["Title"] = twotitle;
dtlist.Rows.Add(drlist);

}

string threetitle = ThreetitleTxtbx.Text;
string threeurl = ThreeurlTxtbx.Text;

if ((threetitle != "" && threetitle != null) && (threeurl != "" && threeurl != null))
{
drlist = dtlist.NewRow();
drlist["URL"] = threeurl;
drlist["Title"] = threetitle;
dtlist.Rows.Add(drlist);
}


string fourtitle = FourtitleTxtbx.Text;
string foururl = FoururlTxtbx.Text;

if ((fourtitle != "" && fourtitle != null) && (foururl != "" && foururl != null))
{
drlist = dtlist.NewRow();
drlist["URL"] = foururl;
drlist["Title"] = fourtitle;
dtlist.Rows.Add(drlist);
}



string fivetitle = FivetitleTxtbx.Text;
string fiveurl = FiveurlTxtbx.Text;

if ((fivetitle != "" && fivetitle != null) && (fiveurl != "" && fiveurl != null))
{
drlist = dtlist.NewRow();
drlist["URL"] = fiveurl;
drlist["Title"] = fivetitle;
dtlist.Rows.Add(drlist);
}

}
else
{
dtlist.Clear();
}

}

// Paypal codings starting

if ( paidtype == "$2.00" || paidtype == "$5.00" )
{

//Pay pal process Refer for what are the variable are need to send http://www.paypalobjects.com/IntegrationCenter/ic_std-variable-ref-buy-now.html

string redirectUrl = "";

// Mention URL to redirect content to paypal site
redirectUrl += "https://www.sandbox.paypal.com/cgi-bin/webscr?cmd=_xclick&business=" + ConfigurationManager.AppSettings["paypalemail"].ToString();


//First name I assign static based on login details assign this value
redirectUrl += "&first_name=Ineeds";

//Product Name
redirectUrl += "&item_name=" + urlTxtbx.Text;

//Product Amount
redirectUrl += "&amount=" + PaidTypeRBL.SelectedValue;

//Business contact paypal EmailID
redirectUrl += "&business=ineedsweb-facilitator@gmail.com";

//Shipping charges if any, or available or using shopping cart system
// redirectUrl += "&shipping=5";

// Handling charges if any, or available or using shopping cart system
// redirectUrl += "&handling=5";

// Tax charges if any, or available or using shopping cart system
// redirectUrl += "&tax=5";

//Quantiy of product, Here statically added quantity 1
redirectUrl += "&quantity=1";

//If transactioin has been successfully performed, redirect SuccessURL page- this page will be designed by developer
redirectUrl += "&return=" +ConfigurationManager.AppSettings["SuccessURL"].ToString();

//If transactioin has been failed, redirect FailedURL page- this page will be designed by developer
redirectUrl += "&cancel_return=" + ConfigurationManager.AppSettings["FailedURL"].ToString();


Response.Redirect(redirectUrl);

}

//Paypal codings ending

int res = Objadmin.Add_DirectoryListing(title, url, desc, name, mail, catid, subid, paidtype, keywords,dtlist);

if (res > 0)
{
Resultlbl.Visible = true;
Resultlbl.Text = "Your URL are added to Directory list and waiting for Approval!";
Clear();
}
else
{
Resultlbl.Visible = true;
Resultlbl.Text = "Your URL are Already Exists in Directory list!";
Clear();
}

}
else
{
Resultlbl.Visible = true;
Resultlbl.Text = "image code is not valid.";
}
this.txtimgcode.Text = "";
}