通过 StringWriter 写入 MemoryStream 会将空字符添加到流中

Question

I have some code in C# where I am trying to write to a MemoryStream via a StringWriter example code:

using (MemoryStream stream = new MemoryStream())
{
  using (StreamWriter writer = new StreamWriter())
  {
    writer.WriteLine("SELECT");
    writer.WriteLine("\tT.*");
    writer.WriteLine("FROM");
    writer.WriteLine("\t[A Table] T");
    writer.WriteLine("WHERE");
    writer.WriteLine($"\tT.[Data Field] IN ({data})");
  }

   ....
  return new MemoryStream(stream.GetBuffer());
}

When I inspect the contents of stream I see that the .NET Framework has added extra 0 bytes to the end of the buffer to take it up to 256 bytes. I can not find anything in the MSDN help and it is puzzling.

To work around this (using the above example) I did the following:

string crlf = Environment.NewLine;


string value = $"SELECT{crlf}";
value += $"\tT.*{crlf}";
value += $"FROM{crlf}";
value += $"\t[A Table] T{crlf}";
value += $"WHERE{crlf}";
value += $"\tT.[Data Field] IN ({data})";


return new MemoryStream(Encoding.UTF8.GetBytes(value));

I would rather use a stream writer than to build up a string and then call Encoding.UTF8.GetBytes(value)

I have tried using a StringBuilder as an intermediary step but it still adds the extra characters to the end.

Answer 1

You're calling stream.GetBuffer() , which returns the underlying buffer the stream writes to - which is almost always larger than the stream. The buffer is expanded automatically when a write would go past the end of it.

You can either use stream.GetBuffer() but also take the stream length into account, and effectively ignore any bytes past that - or call stream.ToArray() instead to get a copy of just the valid data as a new byte array.