Using Group by in DataTable with c#

namesapce testNamespace
{
public partial class testClassName : System.Web.UI
{
private void chkRepeatMtrlsQty(DataTable dtMtrlChk)
    {
   //Pass groupby column names here

        IList<string> _groupByColumnNames = new List<string>();
        _groupByColumnNames.Add("Barcode");
        _groupByColumnNames.Add("MaterialNo");
        _groupByColumnNames.Add("CustPartNo");
        _groupByColumnNames.Add("MtrlDesc");
        _groupByColumnNames.Add("NV");
        _groupByColumnNames.Add("SkuUM");
        _groupByColumnNames.Add("ExtUM");

//Pass Aggregate function column name and alias name here
 IList<DataTableAggregateFunction> _fieldsForCalculation = new List<DataTableAggregateFunction>();
 _fieldsForCalculation.Add(new DataTableAggregateFunction() { enmFunction = AggregateFunction.Sum, ColumnName = "SkuQty", OutPutColumnName = "SkuQty" });
        _fieldsForCalculation.Add(new DataTableAggregateFunction() { enmFunction = AggregateFunction.Sum, ColumnName = "ExtQty", OutPutColumnName = "ExtQty" });

 DataTable dtGroupedBy = GetGroupedBy(dtMtrlChk, _groupByColumnNames, _fieldsForCalculation);
 
    }



private DataTable GetGroupedBy(DataTable _dtSource, IList<string> _groupByColumnNames, IList<DataTableAggregateFunction> _fieldsForCalculation)
    {
        /// <summary>
        /// Group by DataTable
        /// </summary>
        /// <param name="_dtSource"></param>
        /// <param name="_groupByColumnNames"></param>
        /// <param name="_fieldsForCalculation"></param>
        /// <returns></returns>
        //Once the columns are added find the distinct rows and group it bu the numbet
        DataTable _dtReturn = _dtSource.DefaultView.ToTable(true, _groupByColumnNames.ToArray());

        //The column names in data table
        foreach (DataTableAggregateFunction _calculatedField in _fieldsForCalculation)
        {
            _dtReturn.Columns.Add(_calculatedField.OutPutColumnName);
        }

        //Gets the collection and send it back
        for (int i = 0; i < _dtReturn.Rows.Count; i = i + 1)
        {
            #region Gets the filter string
            string _filterString = string.Empty;
            for (int j = 0; j < _groupByColumnNames.Count; j = j + 1)
            {
                if (!string.IsNullOrEmpty(_dtReturn.Rows[i][_groupByColumnNames[j]].ToString()))
                {
                    if (j > 0 && !string.IsNullOrEmpty(_filterString))
                    {
                        _filterString += " AND ";
                    }
                    if (_dtReturn.Columns[_groupByColumnNames[j]].DataType == typeof(System.Int32))
                    {
                        _filterString += _groupByColumnNames[j] + " = " + _dtReturn.Rows[i][_groupByColumnNames[j]].ToString() + "";
                    }
                    else
                    {
                        _filterString += _groupByColumnNames[j] + " = '" + _dtReturn.Rows[i][_groupByColumnNames[j]].ToString() + "'";
                    }
                }
            }
            #endregion

            #region Compute the aggregate command

            foreach (DataTableAggregateFunction _calculatedField in _fieldsForCalculation)
            {
                _dtReturn.Rows[i][_calculatedField.OutPutColumnName] = _dtSource.Compute(_calculatedField.enmFunction.ToString() + "(" + _calculatedField.ColumnName + ")", _filterString);
            }

            #endregion
        }
        return _dtReturn;
    }

}

//create enum function

public enum AggregateFunction
{
    Sum,
    Avg,
    Count,
    Max,
    Min
}

public class DataTableAggregateFunction
{
    /// <summary>
    /// The function to be performed
    /// </summary>
    public AggregateFunction enmFunction { get; set; }

    /// <summary>
    /// Performed for which column
    /// </summary>
    public string ColumnName { get; set; }

    /// <summary>
    /// What should be the name after output
    /// </summary>
    public string OutPutColumnName { get; set; }
}
}