.NET Framework Standard Library Annotated Reference, Volume 1: Base Class Library and Extended Numerics Library

Example

using System;
using System.IO;

namespace Samples
{
  public class FileModeSample
  {
    public static void Main()
    {
      string s = @"FileMode.txt";
      FileMode[] filemodes = {FileMode.Append,
                              FileMode.Create,
                              FileMode.CreateNew,
                              FileMode.Open,
                              FileMode.OpenOrCreate,
                              FileMode.Truncate};
      foreach(FileMode fm in filemodes)
      {
        OpenFile(s, fm,FileAccess.Write);
      }
    }
    private static void OpenFile(string s,
                                 FileMode fm,
                                 FileAccess a)
    {
      try
      {
        using(FileStream fs = File.Open(s, fm, a))
        {
          Console.WriteLine(
             "Can seek in {0} when opened with {1} and {2}: {3}",
                s, a, fm, fs.CanSeek);
        }
      }
      catch(Exception e)
      {
        Console.WriteLine(
           "Cannot open {0} with {1}, reason {2}",
           s, fm, e.Message);
      }
    }
  }
}

The output is

 Can seek in FileMode.txt when opened with Write and Append: ...