Extensions.cs

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;

namespace ExportHistorianTagDataToCSV
{
    static class Extensions
    {
        public static bool In<T>(this T item, params T[] items)
        {
            if (items == null)
                throw new ArgumentNullException("items");

            return items.Contains(item);
        }

        public static DataTable ConvertToDataTable<T>(IEnumerable<T> varlist)
        {
            var dtReturn = new DataTable();

            PropertyInfo[] oProps = null;

            if (varlist == null) return dtReturn;

            foreach (T rec in varlist)
            {
                if (oProps == null)
                {
                    oProps = rec.GetType().GetProperties();

                    foreach (PropertyInfo pi in oProps)
                    {
                        Type colType = pi.PropertyType;

                        if ((colType.IsGenericType) && (colType.GetGenericTypeDefinition() == typeof(Nullable<>)))
                        {
                            colType = colType.GetGenericArguments()[0];
                        }

                        dtReturn.Columns.Add(new DataColumn(pi.Name, colType));
                    }
                }

                DataRow dr = dtReturn.NewRow();

                foreach (PropertyInfo pi in oProps)
                {
                    dr[pi.Name] = pi.GetValue(rec, null) ?? DBNull.Value;
                }

                dtReturn.Rows.Add(dr);
            }
            return dtReturn;
        }
    }
}