Hi Sumit,
Thank you for contacting Infragistics!

The Columns collection contains only columns that you have added to the collection.  It does not contain any autogenerated columns.  You can scan your datasource and create the columns that you need.
In your case:
foreach (DataColumn dataColumn in ((DataTable) wdgRAWNAVReported.DataSource).Columns)
{
if (!dataColumn.Name.ToLower().Contains("portfolio"))
{
var csi = new ColumnSummaryInfo();
csi.ColumnKey = dataColumn.Name;
csi.Summaries.Add(SummaryType.Sum);
var srs = new SummaryRowSetting();
srs.ColumnKey = dataColumn.Name;
srs.FormatString = "{1}";
srs.ShowSummaryButton = false;

wdgRAWNAVReported.Behaviors.SummaryRow.ColumnSummaries.Add(csi);
wdgRAWNAVReported.Behaviors.SummaryRow.ColumnSettings.Add(srs);
}
}

The other way to get columns is form the row items collection. In InitializeRow row event you can use this:
protected void WebDataGrid_InitializeRow(object sender, RowEventArgs e)
    {
        if (e.Row.Index == 0)
        {
            foreach (GridRecordItem field in wdgRAWNAVReported.Rows[0].Items)
            {

                GridField column = field.Column;
                if (!column.Key.Contains("portfolio"))
                {
                    var csi = new ColumnSummaryInfo();
                    csi.ColumnKey = column.Key;
                    csi.Summaries.Add(SummaryType.Count);

                    var srs = new SummaryRowSetting();
                    srs.ColumnKey = column.Key;
                    srs.FormatString = "{1}";
                    srs.ShowSummaryButton = false;

                    wdgRAWNAVReported.Behaviors.SummaryRow.ColumnSummaries.Add(csi);
                    wdgRAWNAVReported.Behaviors.SummaryRow.ColumnSettings.Add(srs);
                }
            }
        }
    }