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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. This is accomplished with the StreamReader class defined within 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 can be used with any file named textfile.txt that contains text or with the file generated in 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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