Monday, July 12, 2010

Impress your colleagues with your knowledge about…the TextFieldParser class

Sometimes when working with C# you discover some hidden gems. Some of them very useful, other ones a little bit harder to find a good way to benefit from their functionality. One of those hidden gems that I discovered some days ago is the TextFieldParser class.

This class is well hidden in the Microsoft.VisualBasic namespace – which makes it not very accessible for the C# developer – although there’s nothing VB.NET specific about it. It makes it very easy to process filetypes like CSV and similar formats.

A quick sample:

   1:  using (var csvFile = new TextFieldParser(myFilePath)  
   2:  {   
   3:        csvFile.TextFieldType = FieldType.Delimited;   
   4:        csvFile.SetDelimiters(",");   
   5:        csvFile.CommentTokens = new[] { "HEADER" };  
   7:        while (!csvFile.EndOfData)  
   8:        {  
   9:            string[] fieldArray;  
  10:            try  
  11:            {  
  12:                fieldArray = csvFile.ReadFields();  
  13:            }  
  14:            catch (Microsoft.VisualBasic.FileIO.MalformedLineException ex)  
  15:           {  
  16:                // TODO: Handle exception  
  17:                continue;  
  18:            }  
  19:            // TODO: process values in fieldArray  
  20:        }  
  21:   }

Some characteristics of this class:

  • There are several constructor overloads, so you can point it to a file path or a stream or TextReader.
  • TextFieldParser implements IDisposable, so you can use it in a "using" block to automatically close the file or stream when finished.
  • The delimiter value can be specified using the  SetDelimiters method.
  • The CommentTokens property is used to tell TextFieldParser to ignore lines where the text begins with one of the specified strings.

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