.txt 文件与 .csv 文件的 C# FileInfo.Length 属性

Question

I am new to C# and new to Visual Studio. I am about half way through a 16 week class in C# using Visual Studio. I felt like I may have learned enough to understand this piece of code from work and modify it. So far I have been able to understand most of it (after many hours, and using google a lot). However, there are a few places that have me stumped... Or maybe the original programmer didn't use very good logic? I don't know... See the code below:

    //This is just a piece of the code... there are hundreds of lines of code above this
    private static void OnSizeChange(object source, FileSystemEventArgs e)
    {
        try
        {
            // SET PATHS FROM WATCHER
            String filePath = e.FullPath;

            FileInfo infoForPath = new FileInfo(e.FullPath);
            //CHECK FOR TEXT FILE IN ORDER TO VERIFY SIZE TO CONFIRM NEW EMPTY FILE WAS NOT CREATED
            String txtExt = ".txt";
            Boolean isTxt = e.FullPath.Contains(txtExt);
            //Length gets the size, in bytes, of the current file.
            if (!isTxt && infoForPath.Length > 5 || isTxt && infoForPath.Length > 0)

What you can not see here is that the file will either be a .txt file or a .csv file. My question is about the if statement.

What is the if statement checking?

From what I can gather, it is checking to see if there is a ".txt" in the file path && the length of the file in bytes is "> 5" (for a non .txt file) or "> 0" (for a .txt file).

What is the reason for the "5" and the "0"?

Is there some inherent reason for these numbers as pertains to .txt and .csv files?

If it helps, i found this code online, which is similar and could be used for testing I think from a C# command prompt application.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        const string fileName = @"C:\programs\file.txt";

        // Part 1: create new FileInfo get Length.
        FileInfo info = new FileInfo(fileName);
        long length = info.Length;

        // Part 2: print length in bytes.
        Console.WriteLine("LENGTH IN BYTES: {0}", length);
    }
}

Output

LENGTH IN BYTES: 60

Answer 1

To start Boolean isTxt = e.FullPath.Contains(txtExt); is error prone and not the best way to do this.

You should instead get the extension by doing var fileExtenstion = infoForPath.Extension this will get you the extension of the file. For more info about this look here . Now that you have the extension you can check if the extension is .txt and return a bool or change how you're if statement works.

The reason for checking for the length of 0 for text files is because text files contain no data (length) when they are empty. I don't know for sure but CSV files may have a default length of 5. You can use the console app code you posted if you want to check this