如何从列表中删除重复项< listviewitem>没有改变它的类型？ [英] How do I remove duplicates from a list<listviewitem> without changing it's type?

问题描述

我有一个List< listviewitem>我将稍后使用.AddRange方法添加到ListView中。该列表包含重复项，因为条目来自不同的来源。



如何从列表< listviewitem>中删除重复项？在不改变元素顺序的情况下改变它的类型，

，使用普通C＃代码（没有外部库）并且没有额外的编码循环来重新使用
填充，删除和检查？



我试过这个对我有用，但之后整个类型都丢失了：



列表< listviewitem> MyList = new List< listviewitem>（）;

//...我的List正在填充并包含重复项...（不包含代码）

List<串GT; tempvar = MyList.Select（x => x.Name）.Distinct（）。ToList（）;



List< string> tempvar基本上包含了我需要的内容，但我需要它作为List< listviewitem>不是List< string>。我是一个初学者，我试过的所有其他东西对我来说都不像Hashing和其他的建议。



后来我执行添加整个列表到listview如下：

MylistView.AddRange（MyList.toArray（））;

在此调用之后我不再检查重复项，代码必须在它之前。



我尝试了什么：



对linq和distinct的不同建议，到目前为止没有任何工作。

I have a List<listviewitem> which I will add later to my ListView with the .AddRange Method. The list contains duplicates because the entries are from different sources.

How do I remove duplicates from a List<listviewitem> without changing its type,
without changing the order of the elements,
with the usage of plain C# code (no external libraries) and without an extra coded loop for re-populating, deleting and checking?

I tried this which works for me, but the whole type is lost afterwards:

List<listviewitem> MyList = new List<listviewitem>();
//...here my List is being populated and contains duplicates... (Code not included)
List<string> tempvar = MyList.Select(x => x.Name).Distinct().ToList();

List<string> tempvar contains basically what I would need, but I need it as a List<listviewitem> not a List<string>. I am a beginner and all other stuff which I tried did not work for me like the Hashing and other sugggestions.

Later I perform the adding of the whole list to the listview as follows:
MylistView.AddRange(MyList.toArray());
After this call I would not check for duplicates anymore, the code must go before it.

What I have tried:

different suggestions for linq and distinct, nothing worked so far.

推荐答案

我的第一个建议，如果可能，将首先收集不同的数据列表然后从在那里为每个创建一个 ListViewItem 。



另一种方式：

尝试使用 .Distinct（）的版本，它带有 IEqualityComparer< TSource> 参数。

例如：

My first suggestion, if possible, would be to collect the list of distinct data first and then go from there to create a ListViewItem for each.

Another way:
Try using the version of .Distinct() that takes an IEqualityComparer<TSource> parameter.
Like:

class LviNameComparer : IEqualityComparer<ListViewItem>
{
  // implement Equals and GetHashCode methods of the interface
  public bool Equals(ListViewItem lvi1, ListViewItem lvi2)
  {
    return ReferenceEquals(lvi1, lvi2) ||
           (lvi1 != null &&
            lvi2 != null &&
            lvi1.Name.Equals(lvi2.Name));
  }

  public int GetHashCode(ListViewItem lvi)
  {
    return lvi == null ? 
           0 :
           (lvi.Name ?? string.Empty).GetHashCode();
  }
}

List<string> tempvar = MyList.Distinct(new LviNameComparer()).ToList();

你'我基本上都在寻找一个.DistinctBy（..）方法，它不包含在标准.NET中，但有一些实现，其中一个可以在这里找到：

GitHub - morelinq / MoreLINQ：LINQ to Objects扩展 [ ^ ]



..允许你这样做：

You're basically looking for a .DistinctBy(..) method, which isn't included in standard .NET but there are implementations, one of which you can find here:
GitHub - morelinq/MoreLINQ: Extensions to LINQ to Objects[^]

..which will allow you to do this:

List<listviewitem> distinctItems = MyList.DistinctBy(x => x.Name).ToList();

编辑：

如果您不想将整个MoreLINQ项目包含在您的解决方案中，请使用以下代码并将其复制到其中拥有C＃-source-file：

If you don't want to include the whole MoreLINQ-project into your solution, use just the following code and copy it into its own C#-source-file:

using System;
using System.Collections.Generic;

namespace LinqExtensions
{
    public static class LinqExtensionDistinctBy
    {
        public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
        {
            HashSet<TKey> keys = new HashSet<TKey>();

            foreach (TSource item in source)
            {
                if (keys.Add(keySelector(item)))
                {
                    yield return item;
                }
            }
        }
    }
}

使用LinqExtensions添加; -directive您要使用此扩展方法的文件。

Add a using LinqExtensions; -directive to your files where you want to use this extension method.

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