Read and write a text file using C#

The sample below is one of the most use functionality in programming.

public static void ReadWriteString(string strInFile, string strOutFile)


   String strLine;


   List<string> strList = new List<string>();

   StreamReader streamReader = new StreamReader(strInFile);


   StreamWriter sw = new StreamWriter(strOutFile);


   while (!streamReader.EndOfStream)


     //Read line

     strLine = streamReader.ReadLine();


     //Write a line of text






Normally people wondering why there is no content after writing to a text file. This is because you did not close the StreamWriter.

Download the complete code from The sample file name is ConAppTextFileReadWrite.rar. My MSN ID is

About chanmingman

Since March 2011 Microsoft Live Spaces migrated to Wordpress ( till now, I have is over 1 million viewers. This blog is about more than 50% telling you how to resolve error messages, especial for Microsoft products. The blog also has a lot of guidance teaching you how to get stated certain Microsoft technologies. The blog also uses as a help to keep my memory. The blog is never meant to give people consulting services or silver bullet solutions. It is a contribution to the community. Thanks for your support over the years. Ming Man is Microsoft MVP since year 2006. He is a software development manager for a multinational company. With 25 years of experience in the IT field, he has developed system using Clipper, COBOL, VB5, VB6, VB.NET, Java and C #. He has been using Visual Studio (.NET) since the Beta back in year 2000. He and the team have developed many projects using .NET platform such as SCM, and HR based applications. He is familiar with the N-Tier design of business application and is also an expert with database experience in MS SQL, Oracle and AS 400.
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2 Responses to Read and write a text file using C#

  1. FireMyst says:

    Here’s a blog which benchmarks 9 common techniques to determine the fastest way to read files using C# .Net:


  2. Johnny Boy says:

    If you have a lot of processing to do within the file itself, the fastest way is to read the entire file contents into an array, close the file, then loop over the array using a Parallel.For loop.

    Benchmarks and sample code here to prove it’s the fastest way to go:

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