ASP.NET

Response.ClearContent()
             Response.AddHeader("content-disposition", "attachment;filename="&  Your File Name  & ".xls")
        Response.Charset = ""
        Response.ContentType = "application/vnd.xls"
        Dim stringWriter As New System.IO.StringWriter()
        Dim htmlWrite As New System.Web.UI.HtmlTextWriter(stringWriter)
'dgview is your datagrid
        dgview.AllowPaging = true
        dgview.DataSource = Your Data Source 
        dgview.DataBind()
        dgview.RenderControl(htmlWrite)
        Response.Write(stringWriter.ToString())
        Response.End()

foreach (DataRow drow in datatable.Rows)
				{
					for (j = 0; j < datatable.Columns.Count; j++)
					{
						
						//if(Headers.Length > k)
						//if(drow[j].ToString() != "" && drow[j].ToString().Length<255)
						if(Headers.Length > k)
						{
							if(datatable.Columns[j].ColumnName == Headers[k].ToString())
							{
								if(drow[j].ToString() != "" )//&& drow[j].ToString().Length<255)
								{
									strRow += drow[j].ToString() + "','";
									
								}
								else
								{
									//							if(datatable.Columns[j].DataType.FullName == "System.String" || datatable.Columns[j].DataType.FullName == "System.DateTime")
									strRow +="-'"+",'";
									//							else
									//								strRow +="0"+",";

								}
								k++;
							}
							//k++;
						}
					}

function applyvalidate(myenableflag) {
        document.all.validate.disabled = true;
        if (myenableflag == true) {
            document.all.validate.disabled = false;
        }
        if (myenableflag == false) {
            document.all.validate.enabled = false;
        }
    }