Hi Debug,

Check this example. now take its reference.

I have used below article to read excel to DataTable.

Read Excel file from FileUpload control without Saving file in ASP.Net

HTML

<asp:FileUpload ID="FileUpload1" runat="server" /><br />
<asp:Button Text="Upload" runat="server" ID="btnUpload" OnClick="OnUpload" /><br /><br />
<asp:GridView runat="server" ID="gvCustomers">
</asp:GridView>

Namespaces

C#

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

VB.Net

Imports System
Imports System.Data
Imports ClosedXML.Excel

Code

C#

protected void OnUpload(object sender, EventArgs e)
{
    using (XLWorkbook workBook = new XLWorkbook(FileUpload1.PostedFile.InputStream))
    {
        IXLWorksheet workSheet = workBook.Worksheet(1);
        DataTable dt = new DataTable();
        bool firstRow = true;
        foreach (IXLRow row in workSheet.Rows())
        {
            if (firstRow)
            {
                foreach (IXLCell cell in row.Cells())
                {
                    dt.Columns.Add(cell.Value.ToString());
                }
                firstRow = false;
            }
            else
            {
                dt.Rows.Add();
                int i = 0;
                foreach (IXLCell cell in row.Cells())
                {
                    dt.Rows[dt.Rows.Count - 1][i] = cell.Value.ToString();
                    i++;
                }
            }
        }

        DataTable dtFinal = new DataTable();
        dtFinal.Columns.AddRange(new DataColumn[3] { 
                        new DataColumn("CustomerId", typeof(string)),
                        new DataColumn("Country", typeof(string)),
                        new DataColumn("Name",typeof(string)) });
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            dtFinal.Rows.Add();
        }

        for (int i = 0; i < dtFinal.Columns.Count; i++)
        {
            string dtFinalColumnName = dtFinal.Columns[i].ColumnName;
            for (int j = 0; j < dt.Columns.Count; j++)
            {
                string dtColumnName = dt.Columns[j].ColumnName;
                if (dtColumnName.ToLower() == dtFinalColumnName.ToLower())
                {
                    for (int k = 0; k < dt.Rows.Count; k++)
                    {
                        DataRow dr = dt.Rows[k];
                        dtFinal.Rows[k][dtFinalColumnName] = dr[dtFinalColumnName];
                        dtFinal.AcceptChanges();
                    }
                    break;
                }
            }
        }
        this.gvCustomers.DataSource = dtFinal;
        this.gvCustomers.DataBind();
    }
}

VB.Net

Protected Sub OnUpload(ByVal sender As Object, ByVal e As EventArgs)
    Using workBook As XLWorkbook = New XLWorkbook(FileUpload1.PostedFile.InputStream)
        Dim workSheet As IXLWorksheet = workBook.Worksheet(1)
        Dim dt As DataTable = New DataTable()
        Dim firstRow As Boolean = True
        For Each row As IXLRow In workSheet.Rows()
            If firstRow Then
                For Each cell As IXLCell In row.Cells()
                    dt.Columns.Add(cell.Value.ToString())
                Next
                firstRow = False
            Else
                dt.Rows.Add()
                Dim i As Integer = 0
                For Each cell As IXLCell In row.Cells()
                    dt.Rows(dt.Rows.Count - 1)(i) = cell.Value.ToString()
                    i += 1
                Next
            End If
        Next
        Dim dtFinal As DataTable = New DataTable()
        dtFinal.Columns.AddRange(New DataColumn(2) {New DataColumn("CustomerId", GetType(Integer)), New DataColumn("Country", GetType(String)), New DataColumn("Name", GetType(String))})
        For i As Integer = 0 To dt.Rows.Count - 1
            dtFinal.Rows.Add()
        Next
        For i As Integer = 0 To dtFinal.Columns.Count - 1
            Dim dtFinalColumnName As String = dtFinal.Columns(i).ColumnName
            For j As Integer = 0 To dt.Columns.Count - 1
                Dim dtColumnName As String = dt.Columns(j).ColumnName
                If dtColumnName.ToLower() = dtFinalColumnName.ToLower() Then
                    For k As Integer = 0 To dt.Rows.Count - 1
                        Dim dr As DataRow = dt.Rows(k)
                        dtFinal.Rows(k)(dtFinalColumnName) = dr(dtFinalColumnName)
                        dtFinal.AcceptChanges()
                    Next
                    Exit For
                End If
            Next
        Next

        Me.gvCustomers.DataSource = dtFinal
        Me.gvCustomers.DataBind()
    End Using
End Sub