Comparing that two text files are identical C#

Question

I'm trying to compare two text files and check if they are identical otherwise I'll be returning false .

The two text files I'm comparing are identical but the result bool is false .

StreamReader sr1 = new StreamReader(@"..\..\..\Test\expected_result_1.txt");                        
StreamReader sr2 = new StreamReader(@"\temp_dir\result01.txt");
result = compareFiles(ref sr1,ref sr2);

And here I have the function:

public bool compareFiles(ref StreamReader file1, ref StreamReader file2)
{
    bool result = true;
    while (!file1.EndOfStream)
    {
        if (file1.Read() != file2.Read())
        {
            result = false;
            break;
        }
    }
    if (result)
    {
        if (!file2.EndOfStream)
        {
            result = false;
        }  
    }
    return result;
} 

Update: The two text files are identical so I compared them in a hex editor and the hex dump was slightly different. What should be done when encountering this issue?

Answer 1

You can simplify your code.

public bool compareFiles(ref StreamReader file1, ref StreamReader file2)
{
  try 
  {
    //Must put that check in a try/catch block, because not every stream
    //supports checking the length.
    if (file1.BaseStream.Length != file2.BaseStream.Length)
      return false;
  } catch {}  //but can safely ignore the exception 

  while (!file1.EndOfStream)
  {
    //once you read different chars from stream, you can return
    if (file1.Read() != file2.Read())
      return false;
  }
  //if you read file1 to the end, file2 must also be at the end 
  return file2.EndOfStream;
}

But in prinicple your code should work too. Maybe you have a linebreak in the end of one file, or some trailing whitespaces, ... Have you tried passing the same file in for both parameters? It should return true.

Answer 2

If the files are small, and if they are text files, which you say they are, then instead of streaming there are higher level methods for file handling. For example:

File.ReadAllText(f1) == File.ReadAllText(f2)

That will compare the contents of 2 files in 1 line without worrying about is 1 stream longer than the other etc.

Of course it is slower this way, but for 1kb you won't notice.

Another pointer, check if you really need to pass variables to a method using 'ref'. That is not required in the code above. Maybe read up on that.