Question

I have a textReader that in a specific instance I want to be able to advance to the end of file quickly so other classes that might hold a reference to this object will not be able to call tr.ReadLine() without getting a null.

This is a large file. I cannot use TextReader.ReadToEnd() as it will often lead to an OutOfMemoryException

I thought I would ask the community if there was a way SEEK the stream without using TextReader.ReadToEnd() which returns a string of all data in the file.

Current method, inefficient.
The following example code is a mock up. Obviously I am not opening a file with an if statement directly following it asking if I want to read to the end.

TextReader tr = new StreamReader("Largefile");
if(needToAdvanceToEndOfFile)
{
    while(tr.ReadLine() != null) { }
}

Desired solution (Note this code block contains fake ‘concept’ methods or methods that cannot be used due to risk of outofmemoryexception)

TextReader tr = new StreamReader("Largefile");
if(needToAdvanceToEndOfFile)
{
    tr.SeekToEnd(); // A method that does not return anything. This method does not exist.
    // tr.ReadToEnd() not acceptable as it can lead to OutOfMemoryException error as it is very large file.
}

A possible alternative is to read through the file in bigger chunks using tr.ReadBlock(args).

I poked around ((StreamReader)tr).BaseStream but could not find anything that worked.

As I am new to the community I figured I would see if someone knew the answer off the top of their head.

Answer 1

You have to discard any buffered data if you have read any file content – since data is buffered you might get content even if you seek the underlying stream to the end – working example:

StreamReader sr = new StreamReader(fileName);
string sampleLine = sr.ReadLine();

//discard all buffered data and seek to end
sr.DiscardBufferedData();
sr.BaseStream.Seek(0, SeekOrigin.End);

The problem as mentioned in the documentation is

The StreamReader class buffers input from the underlying stream when
you call one of the Read methods. If you manipulate the position of
the underlying stream after reading data into the buffer, the position
of the underlying stream might not match the position of the internal
buffer. To reset the internal buffer, call the DiscardBufferedData
method