为什么LINQ中的Union函数不能删除重复的条目? [英] Why doesn't the Union function in LINQ remove duplicate entries?

问题描述

我正在使用VB .NET，我知道Union通常可以使用ByRef，但是在VB中，字符串通常像原始数据类型一样进行处理.

I'm using VB .NET and I know that Union normally works ByRef but in VB, Strings are generally processed as if they were primitive datatypes.

因此，这就是问题所在:

Consequently, here's the problem:

Sub Main()
    Dim firstFile, secondFile As String(), resultingFile As New StringBuilder

    firstFile = My.Computer.FileSystem.ReadAllText(My.Computer.FileSystem.SpecialDirectories.Desktop & "\1.txt").Split(vbNewLine)
    secondFile = My.Computer.FileSystem.ReadAllText(My.Computer.FileSystem.SpecialDirectories.Desktop & "\2.txt").Split(vbNewLine)

    For Each line As String In firstFile.Union(secondFile)
        resultingFile.AppendLine(line)
    Next

    My.Computer.FileSystem.WriteAllText(My.Computer.FileSystem.SpecialDirectories.Desktop & "\merged.txt", resultingFile.ToString, True)
End Sub

1.txt包含:
一个
b
c
d

1.txt contains:
a
b
c
d
e

2.txt包含:
b
c
d
e
f
g
h
我
j

2.txt contains:
b
c
d
e
f
g
h
i
j

运行代码后，我得到:
一个
b
c
d
e
b
f
g
h
我
j

After running the code, I get:
a
b
c
d
e
b
f
g
h
i
j

关于使Union函数像数学函数一样起作用的任何建议吗?

Any suggestions for making the Union function act like its mathematical counterpart?

推荐答案

Linq Union确实可以达到预期的效果.确保输入文件正确(例如，其中一行可能在换行符之前包含空格)或拆分后的Trim()字符串?

Linq Union does perform as you want it to. Ensure your input files are correct (e.g. one of the lines may contain a space before the newline) or Trim() the strings after splitting?

var list1 = new[] { "a", "s", "d" };
var list2 = new[] { "d", "a", "f", "123" };
var union = list1.Union(list2);
union.Dump(); // this is a LinqPad method

在 linqpad 中，结果为{"a", "s", "d", "f", "123" }

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