What do you do when you need to read text from a file in .NET, but you want to start from an offset? This is a slightly niche scenario, but it does happen. Below is a solution to that problem.
To summarize the implementation, you open a file stream, seek to your offset, and then read in the bytes from there. While loading the result I read small chunks into a buffer, decoded them, and then added the decoded string to a string buffer for storage. Please note that if you are using a multibyte encoding then this helper will only work if you use the correct offset.
Helper Code
public class FileHelper
{
private const int BufferSize = 1024;
public static string ReadAllTextFromOffset(
string path,
Encoding encoding,
int offset,
out int totalLength)
{
using (var fs = new FileStream(path, FileMode.Open))
{
totalLength = offset;
if (offset > 0)
{
fs.Seek(offset, SeekOrigin.Begin);
}
var sb = new StringBuilder();
var buffer = new byte[BufferSize];
int readCount;
do
{
readCount = fs.Read(buffer, 0, buffer.Length);
totalLength += readCount;
var subString = encoding.GetString(buffer, 0, readCount);
sb.Append(subString);
}
while (readCount == buffer.Length);
return sb.ToString();
}
}
}
