Some Useful Extension Methods On IList zt

Some Useful Extension Methods On IList<T>

By Peter Bromberg
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Often I need to convert a List of a certain type to a CSV string, or to a DataTable. Here I provide four extension methods: 1) public static DataTable ToDataTable<T>(this IList<T> data) (List<T> to DataTable. 2) public static string ToCsv<T>(this IList<T> data) ( List<T> to CSV string. 3) public static string ToCsv(this DataTable dt) ( DataTable to CSV string. 4) public static void WriteDelimitedFile<T>(this IEnumerable<T> list, string logfile, string delimiter)

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Extension methods are great for utility purposes as there is no need to reference the class in which they are defined, nor to instantiate any objects.

if you have a DataTable "dt" you can simply call dt.ToCsv() to get a CSV delimited string. Likewise if you have a List<Person> "people" you can call people.ToCsv().  I have also included a  public static void WriteDelimitedFile<T>(this IEnumerable<T> list, string logfile, string delimiter) extension method.

Here is the code for the extension methods:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.IO;
using System.Linq;
using System.Text;

namespace ListExtensions
{
  public static  class ListExtensions
    {
       public static DataTable ToDataTable<T>(this IList<T> data)
      {
          PropertyDescriptorCollection props =
              TypeDescriptor.GetProperties(typeof(T));
          DataTable table = new DataTable();
          for (int i = 0; i < props.Count; i++)
          {
              PropertyDescriptor prop = props[i];
               table.Columns.Add(prop.Name, prop.PropertyType);
          }
          object[] values = new object[props.Count];
          foreach (T item in data)
          {
               for (int i = 0; i < values.Length; i++)
              {
                  values[i] = props[i].GetValue(item);
               }
               table.Rows.Add(values);
          }
          return table;
      }

       public static string ToCsv<T>(this IList<T> data)
      {
          PropertyDescriptorCollection props =TypeDescriptor.GetProperties(typeof(T));
          StringBuilder sb = new StringBuilder();
        
          for (int i = 0; i < props.Count; i++)
          {
              PropertyDescriptor prop = props[i];
              sb.Append( prop.Name);
               if (i < props.Count - 1)
               {
                   sb.Append(",");
              }
          }
         sb.Append(Environment.NewLine);
          var values = new object[props.Count];
          foreach (T item in data)
          {
               for (int i = 0; i < values.Length; i++)
              {
                  values[i] = props[i].GetValue(item);
                  sb.Append( values[i].ToString() );
                   if (i < values.Length - 1)
                   {
                        sb.Append(",");
                  }
              }
              sb.Append( Environment.NewLine);
           }
          return sb.ToString();
      }


      public static string ToCsv(this DataTable dt)
      {
          MemoryStream ms = new MemoryStream();
          StreamWriter sw = new StreamWriter(ms);
        int iColCount = dt.Columns.Count;
        for (int i = 0; i < iColCount; i++)
         {
             sw.Write(dt.Columns[i]);
             if (i < iColCount - 1)
             {
                 sw.Write(",");
            }
        }
         sw.Write(sw.NewLine);

        foreach (DataRow dr in dt.Rows)
        {
             for (int i = 0; i < iColCount; i++)
             {
                 if (!Convert.IsDBNull(dr[i]))
                 {
                      sw.Write(dr[i].ToString());
                 }

                 if (i < iColCount - 1)
                 {
                      sw.Write(",");
                 }
             }
             sw.Write(sw.NewLine);
        }
         sw.Close();
          return System.Text.Encoding.UTF8.GetString(ms.ToArray());
      }
    public static void WriteDelimitedFile<T>(this IEnumerable<T> list, string logfile, string delimiter)
       {
           using (var sw = File.AppendText(logfile))
          {
              var props = typeof(T).GetProperties();
              var headerNames = props.Select(x => x.Name);
                   sw.WriteLine(string.Join(delimiter, headerNames.ToArray()));
              foreach (var item in list)
              {
                  var item1 = item;  
                  var values = props
                  .Select(x => x.GetValue(item1, null) ?? "")  
                  .Select(x => x.ToString())
                  .Select(x => x.Contains(delimiter) || x.Contains("\n") ? "\"" + x + "\"" : x);  
                   sw.WriteLine(string.Join(delimiter, values.ToArray()));
               }
               sw.Close();
          }
       }
    }
}

And here is a short Console Application to exercise the above:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Linq;
using System.Text;
using ListExtensions;

namespace ConsoleApplication1
{

    public class Test
   {
       public String Name { get; set; }
       public String Address { get; set; }
       public string City { get; set; }
       public string State { get; set; }
       public string Zipcode { get; set; }
   }
    class Program
    {
         static void Main(string[] args)
        {
           List<Test> tests = new List<Test>();

             for (int i = 0; i < 3; i++)
            {
               Test t = new Test()
                             {
                                 Name = "Peter Bromberg",
                                 Address = "123 High St #10" + i,
                                 City = "Pocahontas",
                                 State = "FL",
                                 Zipcode = "32323"
                             };
                 tests.Add(t);
            }
            DataTable dt = tests.ToDataTable();
            string csv2 = dt.ToCsv();
            string csv = tests.ToCsv();
          
           Console.WriteLine(csv);
           Console.WriteLine("===========================================================");
           Console.WriteLine(csv2);
             tests.WriteDelimitedFile(@"C:\temp\log.csv",",");
           Console.WriteLine("Any key to quit.");
           Console.ReadKey();
        }
    }
}


You can download the Visual Studio 2010 solution here.

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