How to Create a Excel Sheet Using C#

Add this Namespaces

Imports System.Configuration
Imports System.Web
Imports System.Web.Security
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.WebControls.WebParts
Imports System.Web.UI.HtmlControls
Imports System.IO

Write this Code where you want

Dim Path As String = Server.MapPath("SendRequest\" + Filename)
        Dim FileInfor As New FileInfo(Path)
        Dim stringWriter As New StringWriter()
        Dim htmlWrite As New HtmlTextWriter(stringWriter)
        Dim directory__1 As String = Path.Substring(0, Path.LastIndexOf("\"))
        If Not Directory.Exists(directory__1) Then
            Directory.CreateDirectory(directory__1)
        End If
        Dim vw As New System.IO.StreamWriter(Path, True)
        stringWriter.ToString().Normalize()
        vw.Write(stringWriter.ToString())
        vw.Flush()
        vw.Close()
        WriteAttachment(FileInfor.Name, "application/vnd.ms-excel", stringWriter.ToString())

Add this Function also

Public Shared Sub WriteAttachment(ByVal FileName As String, ByVal FileType As String, ByVal content As String)
        Dim Response As HttpResponse = System.Web.HttpContext.Current.Response
        Response.ClearHeaders()
        Response.AppendHeader("Content-Disposition", "attachment; filename=" & FileName)
        Response.ContentType = FileType
        Response.Write(content)
        Response.[End]()
    End Sub