How to store the result of SQL query in Session Variable using ASP.NET C# to use it later

Question

I am new to ASP.NET C#, I am working to develop web forms to send and receive messages (SQL Server as database) like emails. I want to store the result of SQL query in Session Variable and use it later in another page.

Kindly help me how can I do that, please correct if any things goes wrong.

Here is my code:

SqlConnection con = new SqlConnection("Data Source=AZEEM\\SQLEXPRESS; Initial Catalog=kics;User ID=sa;Password=123");
con.Open();

String query = "select username as sender,subject,message from emailtable where receiver='" + Session["username"] + "'";

    enter code here

//this is the query for which I want to store the result in variable myvar, how can I store the result of following query in variable myvar and use it later, when  I execute it, string is shown instead of result of string.
String myvar = "select receiver from emailtable where username='" + Session["username"] + "'";
SqlDataReader reader = null;

SqlCommand cmd = new SqlCommand(query, con);
SqlCommand cmd2 = new SqlCommand(myvar, con);

DataTable dt = new DataTable();
SqlDataAdapter sda = new SqlDataAdapter(cmd);
sda.Fill(dt);
reader = cmd2.ExecuteReader();

GridView1.DataSource = dt;
GridView1.DataBind();
DataSet ds = new DataSet();

ds = myvar;

Answer 1

Try below,

SqlConnection con = new SqlConnection("Data Source=AZEEM\\SQLEXPRESS; Initial Catalog=kics;User ID=sa;Password=123");
con.Open();

String query = "select username as sender,subject,message from emailtable where receiver='" + Session["username"] + "'";

    enter code here

//this is the query for which I want to store the result in variable myvar, how can I store the result of following query in variable myvar and use it later, when  I execute it, string is shown instead of result of string.
String myvar = "select receiver from emailtable where username='" + Session["username"] + "'";
SqlDataReader reader = null;

SqlCommand cmd = new SqlCommand(query, con);
SqlCommand cmd2 = new SqlCommand(myvar, con);

DataTable dt = new DataTable();
SqlDataAdapter sda = new SqlDataAdapter(cmd);
sda.Fill(dt);
reader = cmd2.ExecuteReader();

GridView1.DataSource = dt;
GridView1.DataBind();

session["dt"] = dt;

When you retrieve,

if (session["dt"] != null) {
    DataTable dt = (DataTable)session["dt"];
}

Answer 2

You Need to Pass that Query to this Method which will return you the result Set and then try to assign it to the Session

    String myvar = "select receiver from emailtable where username='" +  Session["username"] + "'";
    Session["myvar"] = GetData(myvar);

Method for GetData as Follows

   private static DataTable GetData(string query)
        {
            DataTable dt = new DataTable();
            string constr = "Data Source=AZEEM\\SQLEXPRESS; Initial Catalog=kics;User ID=sa;Password=123";
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand(query))
                {
                    using (SqlDataAdapter sda = new SqlDataAdapter())
                    {
                        cmd.CommandType = CommandType.Text;
                        cmd.Connection = con;
                        sda.SelectCommand = cmd;
                        sda.Fill(dt);

                    }
                }
                return dt;
            }
        }