Hello guys and good day, I need your help.

This is my net code, I've this error in object dr, why?
Can you help me? Thank you in advance.
PHP Code:
    protected void BindEmployeeDetails()
    {
        
myConnectionString.Open();

        
httpCookie CustInfo Request.Cookies["id"]; 

        
SQL "SELECT * FROM ";
        
SQL SQL " tbl ";
        
SQL SQL " WHERE 1 ";
        
        if (
CustInfo != null)
        {
            
SQL SQL " AND id = " Request.Cookies["id"].ToString() + " ;";
        }

        
OdbcCommand cmd = new OdbcCommand(SQLmyConnectionString);
        
OdbcDataAdapter da = new OdbcDataAdapter(cmd);
        
DataSet ds = new DataSet();
        
da.Fill(ds);
        
OdbcDataReader dr null;


        if (
dr.Read())
        {
            if (
ds.Tables[0].Rows.Count 0)
            {
                
gvDetails.DataSource ds;
                
gvDetails.DataBind();
            }
            else
            {
                
ds.Tables[0].Rows.Add(ds.Tables[0].NewRow());
                
gvDetails.DataSource ds;
                
gvDetails.DataBind();
                
int columncount gvDetails.Rows[0].Cells.Count;
                
gvDetails.Rows[0].Cells.Clear();
                
gvDetails.Rows[0].Cells.Add(new TableCell());
                
gvDetails.Rows[0].Cells[0].ColumnSpan columncount;
                
gvDetails.Rows[0].Cells[0].Text "No record found";
            }
        }
        else
        {
            
Response.Write("No user");
        }

        
myConnectionString.Close();
    }


Exception DetailsSystem.NullReferenceExceptionObject reference not set to an instance of an object.

Source Error:


Line 43:         OdbcDataReader dr null;
Line 44:
Line 45:         if (dr.Read())
Line 46:         {
Line 47:             if (ds.Tables[0].Rows.Count 0