Hey SonaliB,

Please refer below sample.

I have used ClosedXml Libraries to export to Excel.

You can refer below article for more details.

Export DataTable to Excel in ASP.Net using C# and VB.Net

HTML

<div>
    <asp:FileUpload ID="FileUpload1" runat="server" />
    <asp:Button Text="Upload" runat="server" OnClick="ExportToExcel" />
</div>

Namespaces

C#

using System.Data;
using ClosedXML.Excel;
using System.IO;

VB.Net

Imports System.Data
Imports ClosedXML.Excel
Imports System.IO

Code

C#

protected void ExportToExcel(object sender, EventArgs e)
{
    string excelPath = Server.MapPath("~/File/") + Path.GetFileName(FileUpload1.PostedFile.FileName);        
    FileUpload1.SaveAs(excelPath);
    DataSet ds = new DataSet();
    ds.ReadXml(excelPath);
    using (XLWorkbook wb = new XLWorkbook())
    {
        wb.Worksheets.Add(ds.Tables[0], "Customers");

        Response.Clear();
        Response.Buffer = true;
        Response.Charset = "";
        Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
        Response.AddHeader("content-disposition", "attachment;filename=SqlExport.xlsx");
        using (MemoryStream MyMemoryStream = new MemoryStream())
        {
            wb.SaveAs(MyMemoryStream);
            MyMemoryStream.WriteTo(Response.OutputStream);
            Response.Flush();
            Response.End();
        }
    }
}

VB.Net

Protected Sub ExportToExcel(ByVal sender As Object, ByVal e As EventArgs)
    Dim excelPath As String = Server.MapPath("~/File/") + Path.GetFileName(FileUpload1.PostedFile.FileName)
    FileUpload1.SaveAs(excelPath)
    Dim ds As DataSet = New DataSet()
    ds.ReadXml(excelPath)
    Using wb As XLWorkbook = New XLWorkbook()
        wb.Worksheets.Add(ds.Tables(0), "Customers")
        Response.Clear()
        Response.Buffer = True
        Response.Charset = ""
        Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
        Response.AddHeader("content-disposition", "attachment;filename=SqlExport.xlsx")
        Using MyMemoryStream As MemoryStream = New MemoryStream()
            wb.SaveAs(MyMemoryStream)
            MyMemoryStream.WriteTo(Response.OutputStream)
            Response.Flush()
            Response.End()
        End Using
    End Using
End Sub