How to create Temporary Table in asp.net with compute column in C#

using System;

using System.Data;

using System.Configuration;

using System.Collections;

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;

public partial class Default3 : System.Web.UI.Page

{

    Int32 tt;  // tt for total it will calculate the total

    DataTable tb = new DataTable(); //create a instance tb of Datatable

    protected void Page_Load(object sender, EventArgs e)

    {

// here we will create a temporary table of columns under ispostback.

        if (IsPostBack == false)

        {

//”ord” is a datatable type which create a “Table” and “c” for datatable columns.

            DataTable ord = new DataTable("Table"); //the “Table” value must be same for

            DataColumn c = new DataColumn();        // always

            ord.Columns.Add(new DataColumn("value", Type.GetType("System.Int32")));

// “value” is a column name with Int32 datatype.

            ord.Columns.Add(new DataColumn("length", Type.GetType("System.Int32")));

// “length” is a column name with Int32 datatype.

            ord.Columns.Add(new DataColumn("breadth", Type.GetType("System.Int32")));

// “total” is a column name with Int32 datatype.

            ord.Columns.Add(new DataColumn("total", Type.GetType("System.Decimal")));

// “total” is a Expression which calculate the following formula

            ord.Columns["total"].Expression = "value/(length*breadth)";

//storing the structure in “ss” name session.

            Session["ss"] = ord;

           

        }      

    }

    protected void btn_submit_Click(object sender, EventArgs e)

    {

        grdview();// will call the grdview method

    }

// following the temporary table with structure

    private void tempdata()

    {

        tb = (DataTable)(Session["ss"]); //getting the structure from session and

        GridView1.DataSource = tb; // storing in “tb” datatable variable and bind with

        GridView1.DataBind(); // gridview

        Int32 a; Int32 i; ;

        a = tb.Rows.Count; // it will count the total records in the temporary table

    

        for (i = 0; i < a; i++)

        {

            tt += Convert.ToInt32(tb.Rows[i][3]);// will sum the each value

        }

        Label1.Text = tt.ToString();// display in label the total values

    }

    private void grdview()

    {

            //retreiving the structure from session and after creating the new row

// storing the data in rows as index wise. As we know we cannot store Expression column

// in database name is “total” which calculating the formula.

        tb = (DataTable)(Session["ss"]);

        DataRow r1 = tb.NewRow();

        r1[0] = Convert.ToInt32(txt_value.Text);

        r1[1] = Convert.ToInt32(txt_length.Text);

        r1[2] = Convert.ToInt32(txt_breadth.Text);

        tb.Rows.Add(r1);

        GridView1.DataSource = tb; //now binding the gridview with data.

        GridView1.DataBind();

        Int32 a; Int32 i; ;

        a = tb.Rows.Count;

        tt = 0;

        for (i = 0; i < a; i++)

        {

]);// will sum the each value according to index of the column.

            tt += Convert.ToInt32(tb.Rows[i][3]);

        }

        Label1.Text = tt.ToString(); //will store the Total amount of the Square feet..

   

    }

    protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)

    {

        try

        {

            tb = (DataTable)(Session["ss"]);

            tb.Rows.RemoveAt(e.RowIndex); //deleting the records and decreasing the  total

            tempdata(); //calling the tempdata form refresh the output

        }

        catch

        { }

            

    }

}

store the data into database table

*put the below code where u need.
DataTable tb_data = new DataTable();
tb_data = Session(“ss”);    //** here u can store ur all records from session to data table.
savedataintotable();


private void savedataintotable()
{
SqlDataAdapter adp1 = new SqlDataAdapter(“select * from table”, con); //* columnname must be same   
                                                                                                                      table.
SqlCommandBuilder cb = new SqlCommandBuilder(adp1);
DataSet ds1 = new DataSet();
adp1.Fill(ds1);
try {
adp1.Update(tb_data);
} catch (Exception ex) {
}
try
{
tb_data.AcceptChanges()
}
catch (Exception ex) {
}
}
hope it will help u