比较两个文本文件并显示相同的内容

Question

我需要帮助来比较两个文件。我能够打印出两者之间的区别，但是当它们出错时，我无法弄清楚如何打印两者之间的相同之处。谁能帮我？提前感谢！

private void button2_Click(object sender, EventArgs e)
{
try
{
//Reads files line by line
var fileOld = File.ReadLines(Old);
var fileNew = File.ReadLines(New);                              //Ignores cases in files
IEnumerable<String> OldTxt = fileOld.Except(fileNew, StringComparer.OrdinalIgnoreCase);
IEnumerable<String> NewTxt = fileNew.Except(fileOld, StringComparer.OrdinalIgnoreCase);
FileCompare compare = new FileCompare();
bool areSame = OldTxt.SequenceEqual(NewTxt);
if (areSame == true)
{
MessageBox.Show("They match!");
}
else if(areSame == false)
{
// Find the set difference between the two files.  
// Print to Not Equal.txt
var difFromNew = (from file in OldTxt
select file).Except(NewTxt);
using (var file = new StreamWriter(NotEqual))
{
foreach (var notEq in difFromNew)
{
file.WriteLine(notEq.ToString() + "n", true);
}
}
MessageBox.Show("They are not the same! Please look at 'Not Equal.txt' to see the difference. Look at 'Equal.txt' to see what is the same at this time.");
}
}
catch
{
MessageBox.Show("'NewConvert.txt' or 'OldConvert.txt' files does not exist.");
}
}

Answer 1

首先，我认为您的代码中可能存在错误。"fileOld"包含旧文件的所有内容，"OldTxt"仅包含新文件中不存在的旧文件文本。在我的回答之后，请参阅下面的一些代码清理想法。

我认为您正在寻找Intersect，它返回两个 IEnumerable 的共同项目：

var commonItems = fileOld.Intersect(fileNew);

或者，由于您已经有difFromNew中捕获的差异列表，因此您可以再次使用Except：

var difFromNew = fileOld.Except(fileNew); // Note I fixed what I think is a bug here
var commonItems = fileOld.Except(difFromNew);

---

一些潜在的错误：

1. SequenceEqual意味着不仅项目相同，而且顺序相同。如果您确实关心订单，那么这是合适的。问题是这将使显示差异变得困难，因为您用来比较列表的其他方法(Except和Intersect)不关心顺序，只关心项目是否存在。因此，如果fileOld包含cat | dog的项目，而fileNew包含dog | cat的项目，那么它们将不相等，但您也无法显示差异(fileOld.Except(fileNew)将包含0项)。
2. 在diffFromNew列表中，您正在获取OldTxt，这是旧文件中的唯一文本，并针对NewTxt(新文件中的唯一文本)进行Except。这两者之间不能有重叠 - 事实上，默认情况下OldTxt已经包含diffFromNew。

以下是获取所需列表的一种方法：

var oldFilePath = "c:\oldFile.txt";
var newFilePath = "c:\newFile.txt";
var oldFileTxt = File.ReadLines(oldFilePath);
var newFileTxt = File.ReadLines(newFilePath);
// Determine if they're equal by checking if there are not any unique items
var filesAreSame = !oldFileTxt.Except(newFileTxt, StringComparer.OrdinalIgnoreCase).Any();
var commonItems = oldFileTxt.Intersect(newFileTxt, StringComparer.OrdinalIgnoreCase);
var uniqueOldItems = oldFileTxt.Except(commonItems, StringComparer.OrdinalIgnoreCase);
var uniqueNewItems = newFileTxt.Except(commonItems, StringComparer.OrdinalIgnoreCase);

---

以下是这些更改后代码的外观：

if (filesAreSame)
{
MessageBox.Show("They match!");
}
else
{
var commonItems = oldFileTxt.Intersect(newFileTxt, StringComparer.OrdinalIgnoreCase);
var uniqueOldItems = oldFileTxt.Except(commonItems, StringComparer.OrdinalIgnoreCase);
var uniqueNewItems = newFileTxt.Except(commonItems, StringComparer.OrdinalIgnoreCase);
var notEqualsFileText = new StringBuilder();
if (uniqueOldItems.Any())
{
notEqualsFileText.AppendLine(
$"Entries in {oldFilePath} that are not in {newFilePath}:");
notEqualsFileText.AppendLine(string.Join(Environment.NewLine, uniqueOldItems));
}
if (uniqueNewItems.Any())
{
notEqualsFileText.AppendLine(
$"Entries in {newFilePath} that are not in {oldFilePath}:");
notEqualsFileText.AppendLine(string.Join(Environment.NewLine, uniqueNewItems));
}
File.WriteAllText(notEqualFilePath, notEqualsFileText.ToString());
var equalsFileText = new StringBuilder();
if (commonItems.Any())
{
equalsFileText.AppendLine(
$"Entries that are common in both {newFilePath} and {oldFilePath}:");
equalsFileText.AppendLine(string.Join(Environment.NewLine, commonItems));
}
else
{
equalsFileText.AppendLine(
$"There are no common entries in both {newFilePath} and {oldFilePath}.");
}
File.WriteAllText(equalFilePath, equalsFileText.ToString());
MessageBox.Show("The files are not the same! Please look at 'Not Equal.txt' to see the difference. Look at 'Equal.txt' to see what is the same at this time.");
}