比较两个文本文件的特定列值 - C＃

Question

I have a case where I need to compare two text files (using C#), an incoming text file, and an existing text file, checking for changes/differences. Both text files have the same layout, 6 columns of the same type of data and column headers. So this is basically a check to see if the contents of the incoming file has any new data compared to the existing.

The File.ReadAllText method essentially does what I want, the problem is though, I only want to compare the values in the first two columns of the text files, and disregard the other trailing columns.

The text file layout is like the following:

Item #|Total |C3|C4|C5|C6

123|7 |0|0|0|0

So if either the Item # or Total column have a change in the first file compared to the second, the comparing of the files should stop there, and it should be considered a file change.

What is a simple way to approach this? Many thanks.

Answer 1

This is an easy problem when you use string.Split and LINQ's Take and SequenceEqual .

bool AnyDifferent(string file1FullText, string file2FullText)
{
    string[] file1Lines = file1FullText.Split('\n');
    string[] file2Lines = file2FullText.Split('\n');
    if (file1Lines.Length != file2Lines.Length)
        return true;
    for (int i = 0; i < file1Lines.Length; i++)
    {
        var file1LineSplit = file1Lines[i].Split('|');
        var file2LineSplit = file2Lines[i].Split('|');
        if (!file1LineSplit.Take(2).SequenceEqual(file2LineSplit.Take(2)))
            return true;
    }
    return false;
}

Edit or using File.ReadLines for improved performance (you don't have to read the whole files in before you start comparing them):

bool AnyDifferent(string file1Path, string file2Path)
{
    using (var file1Enumerator = File.ReadLines(file1Path).GetEnumerator())
    using (var file2Enumerator = File.ReadLines(file2Path).GetEnumerator())
    {
        while (true)
        {
            bool result1 = file1Enumerator.MoveNext();
            bool result2 = file2Enumerator.MoveNext();
            if (result1 != result2)
                return true;
            else if (!result1 && !result2)
                return false;
            var file1LineSplit = file1Enumerator.Current.Split('|');
            var file2LineSplit = file2Enumerator.Current.Split('|');
            if (!file1LineSplit.Take(2).SequenceEqual(file2LineSplit.Take(2)))
               return true;
        }
    }
}

Answer 2

I would create a class for each Item :

class Item
{
    public int ItemNumber { get; set; }
    public int Total { get; set; }
}

then use a list and compare the data

List<Item> items = new List<Item>();
foreach (String line in File.ReadAllLines("filepath"))
{
    Item item = new Item
    {
         ItemNumber = Convert.ToInt32(line.Split('|')[0]),
         Total = Convert.ToInt32(line.Split('|')[1])
    };
}

then you have a solid structure to compare them with