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How to: Read a Text File (C++/CLI)

The following code example demonstrates how to open and read a text file one line at a time, by using the StreamReader class that's defined in the System.IO namespace. An instance of this class is used to open a text file and then the StreamReader.ReadLine method is used to retrieve each line.

This code example reads a file that's named textfile.txt and contains text. For information about this kind of file, see How to: Write a Text File (C++/CLI).

// text_read.cpp
// compile with: /clr
#using<system.dll>
using namespace System;
using namespace System::IO;

int main()
{
   String^ fileName = "textfile.txt";
   try 
   {
      Console::WriteLine("trying to open file {0}...", fileName);
      StreamReader^ din = File::OpenText(fileName);

      String^ str;
      int count = 0;
      while ((str = din->ReadLine()) != nullptr) 
      {
         count++;
         Console::WriteLine("line {0}: {1}", count, str );
      }
   }
   catch (Exception^ e)
   {
      if (dynamic_cast<FileNotFoundException^>(e))
         Console::WriteLine("file '{0}' not found", fileName);
      else
         Console::WriteLine("problem reading file '{0}'", fileName);
   }

   return 0;
}

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