使用C＃.Net在Text文件中检查新行

Could someone tell me what is the best way to check for a new Line in a Text file? I have a scale, it writes weight values into a text file. Then my C# program has to read out the last value und use it for other calculation. I would read the last line of the text and repeat this after few seconds, but this is a bad solution because it would be better if I could read the last value only then when a new value has been written to file, not every few seconds. So how do I check for a new line in a file? Should I use the file date or file size? Whats the best way? Hope someone can help.Could someone tell me what is the best way to c