I Think you did all the good jobs,

You only need to create the instance here like this

DataTable dt = new DataTable();  

Hi,

 

Please use below code,

 

Hi Naveen,

 

Try to use this one

Also Dont set

 

Session["Buyitem"] = null;

 

instead of use

 

Session["Buyitem"] = dt;

@Jenith

 

Yes, I got the value of dt where You had marked yellow .

This code is in  Cart.aspx Page:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Collections;
using paytm;
namespace WebApplication2
{
public partial class WebForm13 : System.Web.UI.Page
{
int cart_sub_total = 0;
int shiping_cost = 0;
SqlConnection con;
SqlConnection con1;
SqlDataAdapter da;
SqlCommand cmd;
string cons = ConfigurationManager.ConnectionStrings["MyDatabaseConnectionString1"].ConnectionString;
protected void Page_Load(object sender, EventArgs e)
{
lbl_shipping_cost.Text = "70";
if (!IsPostBack)
{
if (Session["Buyitem"] == null)
{
Buy.Enabled = false;
}
}
else
{
Buy.Enabled = true;
}
Session["addproduct"] = true;
DataTable dt = new DataTable();
DataRow dr;
dt.Columns.Add("sno");
dt.Columns.Add("Product_Name");
dt.Columns.Add("ProdImage");
dt.Columns.Add("ProdPrice");

if (Request.QueryString["ProductID"] != null)
{
if (Session["Buyitem"] == null)
{

dr = dt.NewRow();
con = new SqlConnection(cons);
da = new SqlDataAdapter("select * from Product where ProductID=" + Request.QueryString["ProductID"], con);
DataSet ds = new DataSet();
da.Fill(ds);
dr["sno"] = 1;
dr["Product_Name"] = ds.Tables[0].Rows[0]["Product_Name"].ToString();
dr["ProdImage"] = ds.Tables[0].Rows[0]["ProdImage"].ToString();
dr["ProdPrice"] = ds.Tables[0].Rows[0]["ProdPrice"].ToString();
dt.Rows.Add(dr);
GridView1.DataSource = dt;
GridView1.DataBind();
Session["Buyitem"] = dt;
Buy.Enabled = true;
GridView1.FooterRow.Cells[3].Text = "Total Amount Rs.";
GridView1.FooterRow.Cells[4].Text = GrandTotal().ToString();
lbl_cart_sub_total.Text = GrandTotal().ToString();
cart_sub_total = Convert.ToInt32(lbl_cart_sub_total.Text);
shiping_cost = Convert.ToInt32(lbl_shipping_cost.Text);
lbl_total.Text = (cart_sub_total + shiping_cost).ToString();
Response.Redirect("Cartt.aspx");
Session["grandTotal"] = lbl_total.Text;

}
else
{
dt = (DataTable)Session["Buyitem"];
int sr;
sr = dt.Rows.Count;
dr = dt.NewRow();
con1 = new SqlConnection(cons);
da = new SqlDataAdapter("select * from Product where ProductID=" + Request.QueryString["ProductID"], con1);
DataSet ds = new DataSet();
da.Fill(ds);
dr["sno"] = sr + 1;
dr["Product_Name"] = ds.Tables[0].Rows[0]["Product_Name"].ToString();
dr["ProdImage"] = ds.Tables[0].Rows[0]["ProdImage"].ToString();
dr["ProdPrice"] = ds.Tables[0].Rows[0]["ProdPrice"].ToString();
dt.Rows.Add(dr);
GridView1.DataSource = dt;
GridView1.DataBind();
Session["Buyitem"] = dt;
Buy.Enabled = true;
GridView1.FooterRow.Cells[3].Text = "Total Amount Rs.";
GridView1.FooterRow.Cells[4].Text = GrandTotal().ToString();
lbl_cart_sub_total.Text = GrandTotal().ToString();
cart_sub_total = Convert.ToInt32(lbl_cart_sub_total.Text);
shiping_cost = Convert.ToInt32(lbl_shipping_cost.Text);
lbl_total.Text = (cart_sub_total + shiping_cost).ToString();
Response.Redirect("Cartt.aspx");
Session["grandTotal"] = lbl_total.Text;

}
}
else
{
dt = (DataTable)Session["Buyitem"];
GridView1.DataSource = dt;
GridView1.DataBind();
if (GridView1.Rows.Count > 0)
{
GridView1.FooterRow.Cells[3].Text = "Total Amount Rs.";
GridView1.FooterRow.Cells[4].Text = GrandTotal().ToString();
lbl_cart_sub_total.Text = GrandTotal().ToString();
cart_sub_total = Convert.ToInt32(lbl_cart_sub_total.Text);
shiping_cost = Convert.ToInt32(lbl_shipping_cost.Text);
lbl_total.Text = (cart_sub_total + shiping_cost).ToString();
lbl_countcart.Text = GridView1.Rows.Count.ToString();
Session["Cart"] = GridView1.Rows.Count.ToString();
Session["grandTotal"]= lbl_total.Text;
}
}
string orderdate = DateTime.Now.ToShortDateString();
Session["Orderdate"] = orderdate;
orderid();
}
public int GrandTotal()
{
DataTable dt = new DataTable();
dt = (DataTable)Session["Buyitem"];
int nrow = dt.Rows.Count;
int i = 0;
int TotalPrice = 0;
while (i < nrow)
{
TotalPrice = TotalPrice + Convert.ToInt32(dt.Rows[i]["ProdPrice"].ToString());
i = i + 1;
}
return TotalPrice;
}
public void orderid()
{
string alpha = "1234567890";
Random ran = new Random();
char[] myarray = new char[5];
for (int i = 0; i < 5; i++)
{
myarray[i] = alpha[(int)(10 * ran.NextDouble())];
}
string orderid;
orderid = DateTime.Now.Hour.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Day.ToString() + DateTime.Now.Month.ToString() + DateTime.Now.Year.ToString() + new string(myarray) + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString();
Session["OrderID"] = orderid;
}

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow && e.Row.RowIndex != GridView1.EditIndex)
{

}
}

protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
DataTable dt = new DataTable();
dt = (DataTable)Session["Buyitem"];
for (int i = 0; i <= dt.Rows.Count - 1; i++)
{
int sr;
int sr1;
string Qdata;
string Dtdata;
sr = Convert.ToInt32(dt.Rows[i]["sno"].ToString());
TableCell cell = GridView1.Rows[e.RowIndex].Cells[0];
Qdata = cell.Text;
Dtdata = sr.ToString();
sr1 = Convert.ToInt32(Qdata);
if (sr == sr1)
{
dt.Rows[i].Delete();
dt.AcceptChanges();
break;
}
}
for (int i = 1; i <= dt.Rows.Count; i++)
{
dt.Rows[i - 1]["sno"] = i;
dt.AcceptChanges();
}
Session["Buyitem"] = dt;
Response.Redirect("Cartt.aspx");
}
protected void Buy_Click1(object sender, EventArgs e)
{
if (txt_Name.Text == "")
{
string script = "alert(\"Please Enter Name !\");";
ScriptManager.RegisterStartupScript(this, GetType(), "ServerControlScript", script, true);
}
else if (txt_BillingAddress.Text == "")
{
string script = "alert(\"Please Enter Shipping Address !\");";
ScriptManager.RegisterStartupScript(this, GetType(), "ServerControlScript", script, true);
}
else if (txt_PIN.Text == "")
{
string script = "alert(\"Please Enter PIN !\");";
ScriptManager.RegisterStartupScript(this, GetType(), "ServerControlScript", script, true);
}
else if (txt_mob.Text == "")
{
string script = "alert(\"Please Enter Mobile No. !\");";
ScriptManager.RegisterStartupScript(this, GetType(), "ServerControlScript", script, true);
}
else
{
//this.payment();
if (Session["UserID"] != null)
{
string USERID = Session["UserID"].ToString();
string PaymentType = "Paytm";
string PaymentStatus = "NotPaid";
DateTime DateofPurchase = DateTime.Now;
string EMAILID = Session["UserID"].ToString();
string Cust_ID= Session["UserID"].ToString();
string OrderID = Session["OrderID"].ToString();
string Txn_Amount = Session["grandTotal"].ToString();
string CallbackURL = "https://localhost:44348/PaytmPaymentGateway.aspx";
PaytmPayment(EMAILID, Cust_ID, OrderID, Txn_Amount, CallbackURL);
Session["CstmrName"] = txt_Name.Text;
Session["BillingAddress"] = txt_BillingAddress.Text;
Session["Pin"] = txt_PIN.Text;
Session["Mob"] = txt_mob.Text;
//this.getOrderDetail();
}
}

}
public void PaytmPayment(string EMAILID,string Cust_ID,string OrderID,string Txn_Amount,string CallbackURL)
{
string userr = Request.Cookies["BUEMAIL"].Value;
String merchantKey = "AAAAAAAAAAAAAAAAA";
Dictionary parameters = new Dictionary();
parameters.Add("MID", "XXXXXXXXXXXXXXX");
parameters.Add("CHANNEL_ID", "WEB");
parameters.Add("INDUSTRY_TYPE_ID", "Retail");
parameters.Add("WEBSITE", "WEBSTAGING");
parameters.Add("EMAIL", EMAILID);
parameters.Add("MOBILE_NO", "0123456789");
parameters.Add("CUST_ID", Cust_ID);
parameters.Add("ORDER_ID", OrderID);
parameters.Add("TXN_AMOUNT", Txn_Amount);
parameters.Add("CALLBACK_URL", CallbackURL); //This parameter is not mandatory. Use this to pass the callback url dynamically.

string checksum = CheckSum.generateCheckSum(merchantKey, parameters);
string paytmURL = "https://securegw-stage.paytm.in/theia/processTransaction";
string outputHTML = "";
outputHTML = NewMethod(outputHTML);
outputHTML += "";
outputHTML += "";
outputHTML += "";
outputHTML += "

Please do not refresh this page...

";
outputHTML += "

";
outputHTML += "";
outputHTML += "";
foreach (string key in parameters.Keys)
{
outputHTML += "";
}
outputHTML += "";
outputHTML += "";
outputHTML += "";
outputHTML += "";
outputHTML += "

";
outputHTML += "";
outputHTML += "";
Response.Write(outputHTML);

}
private static string NewMethod(string outputHTML)
{
outputHTML += "";
return outputHTML;
}

}
}

 

 

and below code is for PaytmPaymentGateway.aspx Page:

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Collections;
using paytm;
namespace WebApplication2
{
public partial class PaytmPaymentGateway : System.Web.UI.Page
{
SqlConnection con;
SqlCommand cmd;
string cons = ConfigurationManager.ConnectionStrings["MyDatabaseConnectionString1"].ConnectionString;
protected void Page_Load(object sender, EventArgs e)
{
String merchantKey = "XXXXXXXXXXXXXX";
Dictionary parameters = new Dictionary();
string paytmChecksum = "";
foreach (string key in Request.Form.Keys)
{
parameters.Add(key.Trim(), Request.Form[key].Trim());
}

if (parameters.ContainsKey("CHECKSUMHASH"))
{
paytmChecksum = parameters["CHECKSUMHASH"];
parameters.Remove("CHECKSUMHASH");
}

if (CheckSum.verifyCheckSum(merchantKey, parameters, paytmChecksum))
{
string paytmStatus = parameters["STATUS"];
string txnID = parameters["TXNID"];
if (paytmStatus == "TXN_SUCCESS")
{
hiMessage.InnerText = "Payment Success";
pTxnID.InnerText = "Transaction ID :" + txnID;
this.getOrderDetail();
}
else if (paytmStatus == "PENDING")
{
hiMessage.InnerText = "Payment is Pending";
}
else if (paytmStatus == "TXN_FAILURE")
{
hiMessage.InnerText = "Payment Failure !";
}
}
else
{
Response.Write("Checksum MisMatch");
}
}
protected void getOrderDetail()
{
DataTable dt;
dt = (DataTable)Session["Buyitem"];
if (dt != null)
{
for (int i = 0; i <= dt.Rows.Count - 1; i++)
{
con = new SqlConnection(cons);
con.Open();
string sql = ("Insert into OrderDetails(OrderID,ProductName,ProductImage,Price,CustomerName,BillingAddress,OrderDate,OrderStatus)values('" + Session["OrderID"] + "','" + dt.Rows[i]["Product_Name"] + "','" + dt.Rows[i]["ProdImage"] + "','" + dt.Rows[i]["ProdPrice"] + "','" + Session["CstmrName"] + "','" + Session["BillingAddress"] + "','" + Session["Orderdate"] + "','Pending')");
cmd = new SqlCommand(sql, con);
cmd.ExecuteNonQuery();
con.Close();
Session["Buyitem"] = null;
}
}
else
{

}
}

/* protected void Button1_Click(object sender, EventArgs e)
{
this.getOrderDetail();
Response.Redirect("BooksWorld_Index.aspx");
}*/
}
}

 

Plz review the code and helpme 

As @jenith mentioned earlier, check for dt!=null case. if dt have the data it will go through the code and if it doesn't then it won't throw the error.

 

If dt won't be null ever check your code and debug to see where the problem is. use the below code.

Try with this above syntax

Update me it's working or not

if(dt!=null)

{

for(..)

{

} 

}