: System.NullReferenceException: Object reference not set to an instance of an object

using System;
using System.Data;
using System.Configuration;
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;
using System.Data.OracleClient;
public partial class _Default : System.Web.UI.Page 
{
    OracleConnection objConn;
    OracleCommand objCmd;
    String strSQL;

    protected void Page_Load(object sender, EventArgs e)
    {
String strConnString;         
strConnString = "Data Source=pcrm195;User Id=wllnew;Password=wllnew;";         
objConn = new OracleConnection(strConnString);        
objConn.Open();         
if (!Page.IsPostBack)         
{             
BindData();        
} 
    }
    protected void BindData()
    {
        String strSQL;
        strSQL = "SELECT * FROM WLLPACKAGE";

        OracleDataReader dtReader;

        objCmd = new OracleCommand(strSQL, objConn);

        dtReader = objCmd.ExecuteReader();

        //*** BindData to DataGrid ***// 

        myDataGrid.DataSource = dtReader;
        myDataGrid.DataBind();
        dtReader.Close();
        dtReader = null;
    }

 protected void  myDataGrid_CancelCommand(object sender, DataGridCommandEventArgs e)
{
myDataGrid.EditItemIndex = -1;        
myDataGrid.ShowFooter = true;        
BindData(); 
}
protected void  myDataGrid_EditCommand(object sender, DataGridCommandEventArgs e)
{
myDataGrid.EditItemIndex = e.Item.ItemIndex;        
myDataGrid.ShowFooter = false;        
BindData();
}
    protected void myDataGrid_DeleteCommand(object sender, DataGridCommandEventArgs e)
{
strSQL = "DELETE FROM WLLPACKAGE WHERE WLLPACKAGEID = '" + myDataGrid.DataKeys[e.Item.ItemIndex]+"'";        
objCmd = new OracleCommand(strSQL, objConn);       
objCmd.ExecuteNonQuery();           
myDataGrid.EditItemIndex = -1;      
BindData();
}
    protected void myDataGrid_UpdateCommand(object sender, DataGridCommandEventArgs e)
{
TextBox txtWLLPACKAGEID = (TextBox)e.Item.FindControl("txtEditWLLPACKAGEID"); 

TextBox txtWLLPACKAGECODE = (TextBox)e.Item.FindControl("txtWLLPACKAGECODE"); 

TextBox txtWLLPACKAGENAME = (TextBox)e.Item.FindControl("txtEditWLLPACKAGENAME"); 
TextBox txtWLLPACKAGEDESC = (TextBox)e.Item.FindControl("txtEditWLLPACKAGEDESC");        
TextBox txtSDATE = (TextBox)e.Item.FindControl("txtSDATE");         
TextBox txtEDATE = (TextBox)e.Item.FindControl("txtEditEDATE");
TextBox txtSTATUS = (TextBox)e.Item.FindControl("txtEditSTATUS");
TextBox txtBRANDID = (TextBox)e.Item.FindControl("txtEditBRANDID"); 

strSQL = "UPDATE WLLPACKAGE SET WLLPACKAGEID = '" + txtWLLPACKAGEID.Text + "' " +            
" ,WLLPACKAGECODE = '" + txtWLLPACKAGECODE.Text + "' " +
  " ,WLLPACKAGENAME = '" + txtWLLPACKAGENAME.Text + "' " +           
" ,WLLPACKAGEDESC = '" + txtWLLPACKAGEDESC.Text + "' " +            
" ,SDATE= '" + txtSDATE.Text + "' " +           
" ,EDATE= '" + txtEDATE.Text + "' " +           
" ,STATUS= '" + txtSTATUS.Text + "' " +            
" ,BRANDID = '" + txtBRANDID.Text + "' " +           
" WHERE WLLPACKAGEID = '" + myDataGrid.DataKeys[e.Item.ItemIndex] + "'";        
objCmd = new OracleCommand(strSQL, objConn);       
objCmd.ExecuteNonQuery(); 
myDataGrid.EditItemIndex = -1;        
myDataGrid.ShowFooter = true;         
BindData();        
}
    protected void myDataGrid_ItemCommand(object sender, DataGridCommandEventArgs e)
{
    if (e.CommandName == "Add")
    {

        TextBox txtWLLPACKAGEID = (TextBox)e.Item.FindControl("txtAddWLLPACKAGEID");

        TextBox txtWLLPACKAGECODE = (TextBox)e.Item.FindControl("txtAddWLLPACKAGECODE");

        TextBox txtWLLPACKAGENAME = (TextBox)e.Item.FindControl("txtAddWLLPACKAGENAME");

        TextBox txtWLLPACKAGEDESC = (TextBox)e.Item.FindControl("txtAddWLLPACKAGEDESC");

        TextBox txtSDATE = (TextBox)e.Item.FindControl("txtAddSDATE");

        TextBox txtEDATE = (TextBox)e.Item.FindControl("txtAddEDATE");
        TextBox txtSTATUS = (TextBox)e.Item.FindControl("txtAddSTATUS");
        TextBox txtBRANDID = (TextBox)e.Item.FindControl("txtAddBRANDID");

        strSQL = "INSERT INTO WLLPACKAGE (WLLPACKAGEID,WLLPACKAGECODE,WLLPACKAGENAME,WLLPACKAGEDESC,SDATE,EDATE,STATUS,BRANDID) " +

        " VALUES ('" + txtWLLPACKAGEID.Text + "','" + txtWLLPACKAGECODE.Text + "','" + txtWLLPACKAGENAME.Text +"','" + txtWLLPACKAGEDESC.Text + "','" + txtSDATE.Text + "','" + txtEDATE.Text + "','" + txtSTATUS.Text + "','" + txtBRANDID.Text + "')";

        objCmd = new OracleCommand(strSQL, objConn);

        objCmd.ExecuteNonQuery();

        BindData(); 
}



}


}