Export Gridview To Excel File - Error

Question

i use this code for exporting gridview to Excel in asp.net - c#.....but i found some error in my code

i am using stored procedure for sql command and my code behind is as follows....

C# code load event (Calling GetData method)

   public partial class Admin_ResultDisplay : System.Web.UI.Page
   {
    SqlConnection cn;
    SqlCommand cmd = new SqlCommand();

    protected void Page_Load(object sender, EventArgs e)
    {
        cn = new SqlConnection(ConfigurationManager.ConnectionStrings["DbConnect"].ConnectionString);
        cn.Open();

        SqlCommand cmd = (SqlCommand)Session["sqlcmd"];
        DataTable dt = GetData(cmd);
        GridView1.DataSource = dt;
        GridView1.DataBind(); 
    }

here GetData() Method

private DataTable GetData(SqlCommand cmd)
{
    DataTable dt = new DataTable();
    String strConnString = System.Configuration.ConfigurationManager.ConnectionStrings["DbConnect"].ConnectionString;
    //SqlConnection cn = new SqlConnection(strConnString);
    SqlDataAdapter sda = new SqlDataAdapter();

    Session["sqlcmd"] = cmd;
    cmd.CommandType = CommandType.Text;  // <= ERROR POINTED HERE....
    cmd.Connection = cn;
    try
    {
        cn.Open();
        sda.SelectCommand = cmd;
        sda.Fill(dt);
        return dt;
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        cn.Close();
        sda.Dispose();
        cn.Dispose();
    }
}

RAHUL:

As per your guidence i make changes but still gives error....

And ERROR Something like this...it has null value at page_load event thats why it gives error......

Object reference not set to an instance of an object

Answer 1

That's beacuse you are defining cmd in button event as below which is local in scope. If you need it globally then try defining accordingly.

protected void btn_insert_Click(object sender, EventArgs e)    
 {
 try
     {
         SqlCommand cmd = new SqlCommand("GetExamResults", cn); 

EDIT:

If you want to cmd in page_load as well then you can call the SP again in page_load and use it. Like

protected void Page_Load(object sender, EventArgs e) 
 {   
   cn = new SqlConnection(ConfigurationManager.ConnectionStrings     
   ["DbConnect"].ConnectionString);
   SqlCommand cmd = new SqlCommand("GetExamResults", cn);  

But suggest you store the cmd value in session ans reuse it again in page_load like, where your use of cmd getting over

SqlCommand cmd = new SqlCommand();
// Your code goes here

Session["sqlcmd"] = cmd;

In page_load

    protected void Page_Load(object sender, EventArgs e)
    {
        SqlCommand cmd = (SqlCommand)Session["sqlcmd"];

Then use cmd in page_load as well per your need

Answer 2

The error is giving you the information that you need. cmd does, indeed, not exist then. You need to create an instance of SqlCommand in your Page_Load event. From the code you have provided, you are only defining cmd in the button event which is not available to the Page_Load event.