1 ------.aspx-----
 2 <asp:DataGrid id="ItemsGrid"
 3            BorderColor="black"
 4            BorderWidth="1"
 5            CellPadding="3"
 6            AutoGenerateColumns="true"
 7            runat="server">
 8  
 9       asp:DataGrid>
10 
11     <asp:Button ID="btnExcel" runat="server" Text="Excel" OnClick="btnExcelClick" />




 1 ------.cs--------------------
 2 
 3 protected void Page_Load(object sender, EventArgs e)
 4     {
 5         if (!Page.IsPostBack)
 6         {
 7             this.ItemsGrid.DataSource = this.setCreateData();
 8             this.ItemsGrid.DataBind();
 9         }
10     }
11 
12     ICollection setCreateData()
13     {
14         DataTable dt = new DataTable();
15 
16         dt.Columns.Add(new DataColumn("ID", typeof(Int32)));
17         dt.Columns.Add(new DataColumn("File", typeof(String)));
18         dt.Columns.Add(new DataColumn("From", typeof(String)));
19         dt.Columns.Add(new DataColumn("Subject", typeof(String)));
20         dt.Columns.Add(new DataColumn("RegDate", typeof(String)));
21         dt.Columns.Add(new DataColumn("MailSize", typeof(String)));
22         
23         DataRow dr;
24         for (int i = 0; i < 10; i++)
25         {
26             dr = dt.NewRow();
27             dr[0] = i;
28             dr[1] = "fileattach - " + i.ToString();
29             dr[2] = "from - " + i.ToString();
30             dr[3] = "subject - " + i.ToString();
31             dr[4] = "RegDate - " + i.ToString();
32             dr[5] = "MailSize - " + i.ToString();
33             dt.Rows.Add(dr);
34         }
35 
36         DataView dv = new DataView(dt);
37         return dv;
38     }
39     protected void btnExcelClick(object o, EventArgs e)
40     {
41         StringBuilder sb = new StringBuilder(500);
42         sb.Append("아이디, 파일, 기간(From), 제목, 날짜, 사이즈");
43         
44         foreach (DataGridItem item in ItemsGrid.Items) 
45         {
46             sb.Append(Environment.NewLine);
47 
48             for (int i = 0; i < item.Controls.Count; i++)
49             {
50                 sb.Append(((TableCell)item.Controls[i]).Text.Replace(
",", string.Empty)).Append(",");
51             }
52         }
53 
54         DateTime dt = DateTime.Now;
55         string sFileName = "FileName" + "_" + dt.Ticks.ToString() + ".csv";
56 
57         Response.ContentType = "application/vnd.ms-excel";
58         Response.AddHeader(
"Content-Disposition", "attachment;fileName=" + sFileName);
59         Response.Charset = "euc-kr";
60 
61         Response.Clear();
62         Response.Write(sb.ToString());
63         Response.End();
64     }
65 -----
66 --출처는 퍼왔습니다..