File Management

Create, Read, Write, Copy, Move and Delete a Text File using C# and VB.NET

 

In this article, we will explore some common text file operations using C# and VB.NET. This article has been requested by a long time reader of dotnetcurry.com. NET provides various classes like the File and FileInfo, to create, read, write and perform such similar operations on a text file. For example, you can use the Create() method of the File class to create a text file. The same could also be done using the CreateText() method of the FileInfo class. Similarly these classes also contain functionality to copy, move or delete a file. The trick is to find out when to use which class and for what purpose.

The ‘File’ class contains static methods and performs security checks on all the methods. The FileInfo contains instance methods and security check is not necessary. So this method is useful if you plan to use the same instance of the class in multiple operations.

However for copying, moving or deleting the files, the static methods are faster. Moreover, the Garbage Collector has less work to do when you use the File class, since the methods are static.

For reading and writing text files, we have some abstract classes like the TextReader and TextWriter classes. There are some useful classes like the StreamReader, StringReader, StreamWriter and StringWriter that derive from these abstract classes.

This article is by no means a comprehensive guide to demonstrate the capabilities of these classes. It should be treated as a ‘How do I’ kind of a series to demonstrate some of the capabilities of these classes. I will be giving some references at the end of this article, which should be read to gain a better understanding of these classes. Let us now see some code which demonstrates how to use these classes.

Before you go ahead and use these methods, declare a class variable called ‘fileLoc’ which contains the filepath of the text file.

C#

string fileLoc = @"c:\sample1.txt";

VB.NET

Dim fileLoc As String = "c:\sample1.txt"

You would also need to reference the System.IO namespace in your project.

 

Create a Text File

 

C#

       // Create a Text File

        private void btnCreate_Click(object sender, EventArgs e)

        {

            FileStream fs = null;

            if (!File.Exists(fileLoc))

            {

                using (fs = File.Create(fileLoc))

                {

 

                }

            }

        }

VB.NET

         ' Create a Text File

            Private Sub btnCreate_Click(ByVal sender As Object, ByVal e As EventArgs)

                  Dim fs As FileStream = Nothing

                  If (Not File.Exists(fileLoc)) Then

                        fs = File.Create(fileLoc)

                        Using fs

 

                        End Using

                  End If

            End Sub

 

Write to a Text File

 

C#

        // Write to a Text File

        private void btnWrite_Click(object sender, EventArgs e)

        {

            if (File.Exists(fileLoc))

            {

                using (StreamWriter sw = new StreamWriter(fileLoc))

                {

                    sw.Write("Some sample text for the file");                  

                }

            }

        }

 

VB.NET

            ' Write to a Text File

            Private Sub btnWrite_Click(ByVal sender As Object, ByVal e As EventArgs)

                  If File.Exists(fileLoc) Then

                        Using sw As StreamWriter = New StreamWriter(fileLoc)

                              sw.Write("Some sample text for the file")

                        End Using

                  End If

            End Sub

 

Read From a Text File

 

C#

        // Read From a Text File

        private void btnRead_Click(object sender, EventArgs e)

        {

            if (File.Exists(fileLoc))

            {

                using (TextReader tr = new StreamReader(fileLoc))

                {

                    MessageBox.Show(tr.ReadLine());

                }

            }

        }

VB.NET

            ' Read From a Text File

            Private Sub btnRead_Click(ByVal sender As Object, ByVal e As EventArgs)

                  If File.Exists(fileLoc) Then

                        Using tr As TextReader = New StreamReader(fileLoc)

                              MessageBox.Show(tr.ReadLine())

                        End Using

                  End If

            End Sub

 

Copy a Text File

 

C#

        // Copy a Text File

        private void btnCopy_Click(object sender, EventArgs e)

        {

            string fileLocCopy = @"d:\sample1.txt";

            if (File.Exists(fileLoc))

            {

                // If file already exists in destination, delete it.

                if (File.Exists(fileLocCopy))

                    File.Delete(fileLocCopy);

                File.Copy(fileLoc, fileLocCopy);

            }

        }

VB.NET

            ' Copy a Text File

            Private Sub btnCopy_Click(ByVal sender As Object, ByVal e As EventArgs)

                  Dim fileLocCopy As String = "d:\sample1.txt"

                  If File.Exists(fileLoc) Then

                        ' If file already exists in destination, delete it.

                        If File.Exists(fileLocCopy) Then

                              File.Delete(fileLocCopy)

                        End If

                        File.Copy(fileLoc, fileLocCopy)

                  End If

            End Sub

 

Move a Text File

 

C#

        // Move a Text file

        private void btnMove_Click(object sender, EventArgs e)

        {

            // Create unique file name

            string fileLocMove = @"d:\sample1" + System.DateTime.Now.Ticks + ".txt";

            if (File.Exists(fileLoc))

            {

                File.Move(fileLoc, fileLocMove);

            }

        }

VB.NET

            ' Move a Text file

            Private Sub btnMove_Click(ByVal sender As Object, ByVal e As EventArgs)

                  ' Create unique file name

                  Dim fileLocMove As String = "d:\sample1" & System.DateTime.Now.Ticks & ".txt"

                  If File.Exists(fileLoc) Then

                        File.Move(fileLoc, fileLocMove)

                  End If

            End Sub

 

Delete a Text File

 

C#

       // Delete a text file

        private void btnDelete_Click(object sender, EventArgs e)

        {

            if (File.Exists(fileLoc))

            {

                File.Delete(fileLoc);

            }

        }

VB.NET

         ' Delete a text file

            Private Sub btnDelete_Click(ByVal sender As Object, ByVal e As EventArgs)

                  If File.Exists(fileLoc) Then

                        File.Delete(fileLoc)

                  End If

            End Sub

 

Another Example

Here is a simple general way to write to a text file:

// FileWrite - write input from the Console into a text file

using System;
using System.IO;

namespace FileWrite
{
  public class Class1
  {
    public static void Main(string[] args)
    {
      // create the filename object - the while loop allows
      // us to keep trying with different filenames until
      // we succeed
      StreamWriter sw = null;
      string sFileName = "";
      while(true)
      {
        try
        {
          // enter output filename (simply hit Enter to quit)
          Console.Write("Enter filename "
                      + "(Enter blank filename to quit):");
          sFileName = Console.ReadLine();
          if (sFileName.Length == 0)
          {
            // no filename - this jumps beyond the while
            // loop to safety
            break;
          }

          // open file for writing; throw an exception if the
          // file already exists:
          //   FileMode.CreateNew to create a file if it
          //                   doesn't already exist or throw
          //                   an exception if file exists
          //   FileMode.Append to create a new file or append
          //                   to an existing file
          //   FileMode.Create to create a new file or 
          //                   truncate an existing file

          //   FileAccess possibilities are:
          //                   FileAccess.Read, 
          //                   FileAccess.Write,
          //                   FileAccess.ReadWrite
          FileStream fs = File.Open(sFileName, 
                                    FileMode.CreateNew, 
                                    FileAccess.Write);

          // generate a file stream with UTF8 characters
          sw = new StreamWriter(fs, System.Text.Encoding.UTF8);

          // read one string at a time, outputting each to the
          // FileStream open for writing
          Console.WriteLine("Enter text; enter blank line to stop");
          while(true)
          {
            // read next line from Console;
            // quit if line file is blank
            string sInput = Console.ReadLine();
            if (sInput.Length == 0)
            {
              break;
            }

            // write the line just read to output file
            sw.WriteLine(sInput);
          }

          // close the file we just created
          sw.Close();
          sw = null;
        }
        catch(IOException fe)
        {
          // whoops -- an error occurred somewhere during
          // the processing of the file - tell the user 
          // what the full name of the file is:
          // take the path name onto the filename
          string sDir = Directory.GetCurrentDirectory();
          string s = Path.Combine(sDir, sFileName);
          Console.WriteLine("Error on file {0}", s);

          // now output the error message in the exception
          Console.WriteLine(fe.Message);
        }
      }

      // wait for user to acknowledge the results
      Console.WriteLine("Press Enter to terminate...");
      Console.Read();
    }
  }
}