C# 从数据集中获取列的所有值
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Get all values of a column from a DataSet
提问by Nelson Reis
In C#, is it possible to get all values of a particular column from all rows of a DataSet with a simple instruction (no LINQ, no For cicle)?
在 C# 中，是否可以使用简单的指令（没有 LINQ，没有 For cicle）从 DataSet 的所有行中获取特定列的所有值？
采纳答案by Jeff Sternal
Only by iterating over the rows, as Utaal noted in this answer.
正如Utaal 在这个答案中指出的那样，只能遍历行。
You might expect that the DataTable.DefaultView.RowFilterwould support grouping, but it does not (it mainly offers the equivalent functionality of a Whereclause, with some basic aggregations - though not simple grouping).
您可能期望DataTable.DefaultView.RowFilter将支持分组，但它不支持（它主要提供Where子句的等效功能，以及一些基本聚合 - 尽管不是简单的分组）。
回答by Utaal
As far as I know there's no direct way to get those; but the for-loop is pretty straightforward and obviously won't be more resource-intensive than anything else.
据我所知，没有直接的方法可以得到这些；但是 for 循环非常简单，显然不会比其他任何东西都更占用资源。
回答by Welbog
In addition to Utaal's answer, you can possibly populate a new DataTable object with the results of a query that selects only one column from your original data source, assuming it's an RDBMS. This has the advantage of letting you specify things that are easy to express in code but easy to express in SQL like DISTINCTqueries.
除了 Utaal 的答案之外，您还可以使用从原始数据源中仅选择一列的查询结果填充新的 DataTable 对象，假设它是一个 RDBMS。这样做的好处是让您指定易于用代码表达但易于用 SQL 表达的事物，如DISTINCT查询。
回答by KyleMit
Why No LINQ? For people coming here without the same restriction, here are three ways to do this, the bottom two both using LINQ.
为什么没有 LINQ？对于没有同样限制来到这里的人，这里有三种方法可以做到这一点，底部两种都使用 LINQ。
C#
C＃
List<object> colValues = new List<object>();
//for loop
foreach (DataRow row in dt.Rows) {
colValues.Add(row["ColumnName"]);
}
//LINQ Query Syntax
colValues = (from DataRow row in dt.Rows select row["ColumnName"]).ToList();
//LINQ Method Syntax
colValues = dt.AsEnumerable().Select(r => r["ColumnName"]).ToList();
VB
VB
Dim colValues As New List(Of Object)
'for loop
For Each row As DataRow In dt.Rows
colValues.Add(row("ColumnName"))
Next
'LINQ Query Syntax
colValues = (From row As DataRow In dt.Rows Select row("ColumnName")).ToList
'LINQ Method Syntax
colValues = dt.Rows.AsEnumerable.Select(Function(r) r("ColumnName")).ToList
To use the AsEnumerablemethod on a DataTable, you'll have to have a Reference to System.Data.DataSetExtensions which add the LINQ extension methods. Otherwise, you can just cast the Rowsproperty of the DataTableas type DataRow(you don't have to do this with the Query syntax because it automatically casts for you).
要AsEnumerable在 a 上使用该方法DataTable，您必须有一个对 System.Data.DataSetExtensions 的引用，它添加了LINQ 扩展方法。否则，您可以只转换as 类型的Rows属性（您不必使用 Query 语法执行此操作，因为它会自动为您转换）。DataTableDataRow
