与 IEnumerable 列表一起使用的聚合方法

发布于 2024-10-30 22:26:14 字数 635 浏览 1 评论 0原文

当不同类型在其构造函数中接受前一种类型时，是否有一种方法可以将例如字符串的 IEnumerable 列表“转换”（返回）为不同类型的 IEnumerable 列表？

例如，DataTable.Columns.AddRange() 方法仅接受列列表。有没有办法通过使用 LINQ 或某种聚合函数提供 string 列表来返回 DataColumn 列表？我想代码大致会执行以下操作，但在一行中：

var columnList = new List<DataColumn>();
foreach (var item in myStringList)
{
    columnList.Add(item);
}
return columnList;

同样，是否有一种聚合方法将获取一个列表并针对特定方法运行其每个成员？例如，我正在寻找一种单行方法来执行以下类似的 foreach 循环：

foreach (var item in myStringList)
{
    myDataTable.Columns.Add(item);
}

显然，我正在寻找实际上并不依赖于数据列或字符串的通用答案。

原文

Is there a way to "convert" (return) an IEnumerable list of, e.g., strings to an IEnumerable list of a different type when that different type accepts the former type in its constructor?

For example, the DataTable.Columns.AddRange() method accepts only lists of columns. Is there a way to return a DataColumn list by offering a string list using LINQ or some sort of aggregate function? I imagine the code would roughly do the following, but in one line:

var columnList = new List<DataColumn>();
foreach (var item in myStringList)
{
    columnList.Add(item);
}
return columnList;

Likewise, is there an aggregate method that will take a list and run each of its members against a specific method? For example, I am looking for a one line way to perform the following similar foreach loop:

foreach (var item in myStringList)
{
    myDataTable.Columns.Add(item);
}

Obviously, I am looking for generic answers that are not actually dependent on data columns or strings.

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榆西 2024-11-06 22:26:14

您可以编写

var newList = list.ConvertAll(x => new Something(x));
list.ForEach(x => DoSomething(x));

这些方法由 List 类定义。

如果您有任意 IEnumerable，则可以使用 LINQ：

var newEnumerable = enumerable.Select(x => new Something(x));

You can write

var newList = list.ConvertAll(x => new Something(x));
list.ForEach(x => DoSomething(x));

These methods are defined by th List<T> class.

If you have an arbitrary IEnumerable<T>, you can use LINQ:

var newEnumerable = enumerable.Select(x => new Something(x));

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无人问我粥可暖 2024-11-06 22:26:14

调用 Enumerable.Aggregate

List<DataColumn> result = myStringList.Aggregate(
  new List<DataColumn>(),
  (list, item) => { list.Add(item); return list; }
);

return result;

也就是说，foreach 语句更好。

Call Enumerable.Aggregate

List<DataColumn> result = myStringList.Aggregate(
  new List<DataColumn>(),
  (list, item) => { list.Add(item); return list; }
);

return result;

That said, foreach statement is better.

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折戟 2024-11-06 22:26:14

是的，事实上，尽管并非所有这些都是特定于 LINQ 的。 ForEach 只是一个 List 方法。对于您的两个示例：

myStringList.ForEach(x => columnList.Add(x));
// assumes myStringList is a List<T>... otherwise convert your enumerable using ToList()

ForEach 方法采用一个操作，并允许您对每个项目执行一些逻辑。因此，如果你想进行转换，与 select 结合起来就很容易了：

myStringList.Select(x => new DataColumn(x))
      .ToList()
      .ForEach(x => columnList.Add(x));
// transforms each element of the string by adding some text, then calling foreach 
// on the items

Yes, in fact, although not all of them are LINQ specific. ForEach is just a List method. For your two examples:

myStringList.ForEach(x => columnList.Add(x));
// assumes myStringList is a List<T>... otherwise convert your enumerable using ToList()

The ForEach method takes an Action and lets you perform some logic on each item. So if you want to do transformations, it's easy enough combining with select:

myStringList.Select(x => new DataColumn(x))
      .ToList()
      .ForEach(x => columnList.Add(x));
// transforms each element of the string by adding some text, then calling foreach 
// on the items

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