Pivoting DataTable Simplified

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;

// Written by Anurag Gandhi.
// Url: http://www.gandhisoft.com
// Contact me at: soft.gandhi@gmail.com
public partial class _Default : System.Web.UI.Page 
{
    string _Separator = ".";

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindGridView();
        }
    }

    //Binds all the GridView used in the page.//
    private void BindGridView()
    {
        // Retrieve the data table from Excel Data Source.
        DataTable dt = ExcelLayer.GetDataTable("_Data\\DataForPivot.xls", "Sheet1$");  
        Pivot pvt = new Pivot(dt);

        grdRawData.DataSource = dt;
        grdRawData.DataBind();

        grdCompanyYear.DataSource = pvt.PivotData("Company", "CTC", AggregateFunction.Count, "Year");
        grdCompanyYear.DataBind();
        grdLeastCompanyYear.DataSource = pvt.PivotData("Company", "CTC", AggregateFunction.Min, "Year");
        grdLeastCompanyYear.DataBind();

        grdDesignationCompanyYear.DataSource = pvt.PivotData("Designation", "CTC", AggregateFunction.Max, "Company", "Year");
        grdDesignationCompanyYear.DataBind();
        grdDesignationCompanyYearAvg.DataSource = pvt.PivotData("Designation", "CTC", AggregateFunction.Average, "Company", "Year");
        grdDesignationCompanyYearAvg.DataBind();

        grdPivot.DataSource = pvt.PivotData("Designation", "CTC", AggregateFunction.Max, "Company", "Department", "Year");
        grdPivot.DataBind();
    }
    protected void grdPivot2_RowCreated(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.Header)
            MergeHeader((GridView)sender, e.Row, 2);
    }
    protected void grdPivot3_RowCreated(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.Header)
            MergeHeader((GridView)sender, e.Row, 3);
    }

    /// <summary>
    /// Function used to Create and Merge the Header Cells based on the Pivot conditions.
    /// </summary>
    /// <param name="gv">GridView</param>
    /// <param name="row">Header Row of the GridView</param>
    /// <param name="PivotLevel">The no. of ColumnFields used to Pivot the data</param>
    private void MergeHeader(GridView gv, GridViewRow row, int PivotLevel)
    {
        for (int iCount = 1; iCount <= PivotLevel; iCount++)
        {
            GridViewRow oGridViewRow = new GridViewRow(0, 0, DataControlRowType.Header, DataControlRowState.Insert);
            var Header = (row.Cells.Cast<TableCell>()
                .Select(x => GetHeaderText(x.Text, iCount, PivotLevel)))
                .GroupBy(x => x);

            foreach (var v in Header)
            {
                TableHeaderCell cell = new TableHeaderCell();
                cell.Text = v.Key.Substring(v.Key.LastIndexOf(_Separator) + 1);
                cell.ColumnSpan = v.Count();
                oGridViewRow.Cells.Add(cell);
            }
            gv.Controls[0].Controls.AddAt(row.RowIndex, oGridViewRow);
        }
        row.Visible = false;
    }
    private string GetHeaderText(string s, int i, int PivotLevel)
    {
        if (!s.Contains(_Separator) && i != PivotLevel)
            return string.Empty;
        else
        {
            int Index = NthIndexOf(s, _Separator, i);
            if (Index == -1)
                return s;
            return s.Substring(0, Index);
        }
    }

    /// <summary>
    /// Returns the nth occurance of the SubString from string str
    /// </summary>
    /// <param name="str">source string</param>
    /// <param name="SubString">SubString whose nth occurance to be found</param>
    /// <param name="n">n</param>
    /// <returns>Index of nth occurance of SubString if found else -1</returns>
    private int NthIndexOf(string str, string SubString, int n)
    {
        int x = -1;
        for (int i = 0; i < n; i++)
        {
            x = str.IndexOf(SubString, x + 1);
            if (x == -1)
                return x;
        }
        return x;
    }
}