title: Error: The type or namespace name 'ExcelPackage' could not be found
body: <p>I like to make excel file when I press the the button with below code, but I have 2 errors.</p>
  
  <pre><code>Error 1: The type or namespace name 'ExcelPackage' could not be found
  
  Error 2: var ds = query.CopyToDataTable();
  </code></pre>
  
  <p>the code for button click event is like below:</p>
  
  <pre><code>using System;
  using System.Collections;
  using System.Configuration;
  using System.Data;
  using System.Linq;
  using System.Web;
  using System.Web.Security;
  using System.Web.UI;
  using System.Web.UI.HtmlControls;
  using System.Web.UI.WebControls;
  using System.Web.UI.WebControls.WebParts;
  using System.Xml.Linq;
  using System.Data.OleDb;
  using Microsoft.Office.Interop.Excel;
  using Microsoft.Office.Core;
  using System.Reflection;
  using System.ComponentModel;
  using System.Collections.Generic;
  using System.Data.Linq;
  using System.Data.SqlClient;
  using System.Drawing;
  using System.Text;
  
  
  public partial class Default2 : System.Web.UI.Page
  {
      protected void Page_Load(object sender, EventArgs e)
      {
  
      }
      protected void Button1_Click(object sender, EventArgs e)
      {
          var p = new ExcelPackage();
          var sheetName = "MyWorksheet";
          ExcelWorksheet ws = p.Workbook.Worksheets.Add(sheetName);
  
  
          ws.Cells.Style.Font.Size = 11; //Default font size for whole sheet
          ws.Cells.Style.Font.Name = "Calibri"; //Default Font name for whole sheet
  
          LinqBooksDataSet dataSet = new LinqBooksDataSet();
          FillDataSetUsingLinqToSql2(dataSet);
  
          // Query the DataTables
          var query =
           from publisher in dataSet.Publisher
          join book in dataSet.Book
          on publisher.ID equals book.Publisher
          select new
         {
      Publisher = publisher.Name,
      Book = book.Title
  };
  
          var ds = query.CopyToDataTable();
  
          if (ds.Tables.Count &gt; 0 &amp;&amp; ds.Rows.Count &gt; 0)
          {
              ws.Cells["A1"].LoadFromDataTable(ds, true);
              Response.BinaryWrite(p.GetAsByteArray());
              Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
              Response.AddHeader("content-disposition", "attachment;  filename=" + sheetName + ".xlsx");
          }
  
      }
      private static void FillDataSetUsingLinqToSql2(LinqBooksDataSet dataSet)
      {
          // Prepare the LINQ to SQL DataContext
          var linqBooks = new LinqBooksDataContext();
  
          // Query the Publisher table
          var publisherQuery =
            from publisher in linqBooks.Publishers
            select new { publisher.ID, publisher.Name };
          // Query the Book table
          var bookQuery =
            from book in linqBooks.Books
            where book.PubDate.Value.Year &gt; 1950
            select new
            {
                book.ID,
                book.Title,
                book.Subject
  
  
            };
  
          // Execute the queries and load the data into the DataSet
          foreach (var publisher in publisherQuery)
          {
              dataSet.Publisher.AddPublisherRow(
              publisher.ID, publisher.Name, null, null);
          }
          foreach (var book in bookQuery)
          {
              dataSet.Book.AddBookRow(book.ID, book.Title, book.Subject);
  
          }
      }
  }
  </code></pre>