.NET中如何对List中的数据进行部分转置？

以下是针对你的场景（从时序数据库获取的VoltageList（继承自List(Of Voltage)）转置需求）的几种.NET技术实现方案，均适配VB.NET环境：

1. LINQ 查询（最常用、代码简洁） #

利用LINQ的投影与集合转换能力，适合通道数量固定的结构化场景。假设你的Voltage类及目标转置类定义如下：

Public Class Voltage
    Public Property Timestamp As DateTime
    Public Property Channel1 As Double?
    Public Property Channel2 As Double?
    ' 扩展其他电压通道属性...
End Class

Public Class VoltageList
    Inherits List(Of Voltage)
    Public Function Transpose() As List(Of ChannelVoltage)
        ' 实现逻辑见下方
    End Function
End Class

' 转置后的目标数据结构示例
Public Class ChannelVoltage
    Public Property ChannelName As String
    Public Property Values As List(Of (Timestamp As DateTime, Value As Double?))
End Class

Transpose方法的LINQ实现：

Public Function Transpose() As List(Of ChannelVoltage)
    ' 定义通道映射：通道名称 → 取值逻辑
    Dim channelMappings = {
        ("Channel1", Function(v As Voltage) v.Channel1),
        ("Channel2", Function(v As Voltage) v.Channel2)
        ' 按需添加更多通道
    }

    Return channelMappings.Select(Function(map) New ChannelVoltage With {
        .ChannelName = map.Item1,
        .Values = Me.Select(Function(v) (v.Timestamp, map.Item2(v))).ToList()
    }).ToList()
End Function

2. 反射（处理动态通道场景） #

如果Voltage类的电压通道属性数量不固定（动态增减），可通过反射自动遍历属性实现转置，无需硬编码通道名称：

Imports System.Reflection

Public Function Transpose() As List(Of ChannelVoltage)
    Dim result As New List(Of ChannelVoltage)()
    
    ' 获取Voltage类中除Timestamp外的所有数值型属性（即电压通道）
    Dim channelProperties = GetType(Voltage).GetProperties() _
        .Where(Function(p) 
            p.Name <> NameOf(Voltage.Timestamp) AndAlso 
            (p.PropertyType Is GetType(Double) OrElse p.PropertyType Is GetType(Double?))
        ).ToList()

    For Each prop In channelProperties
        result.Add(New ChannelVoltage With {
            .ChannelName = prop.Name,
            .Values = Me.Select(Function(v) (v.Timestamp, CType(prop.GetValue(v), Double?))).ToList()
        })
    Next

    Return result
End Function

优化提示：可缓存channelProperties集合避免重复反射，提升性能。

3. DataTable 转置（兼容传统数据交互） #

若需转置后的数据与WinForms/WPF数据控件（如DataGridView）直接交互，可先将VoltageList转换为DataTable，再完成行列转置：

Imports System.Data

Public Function Transpose() As DataTable
    ' 1. 填充原始数据到DataTable
    Dim sourceTable As New DataTable()
    sourceTable.Columns.Add(NameOf(Voltage.Timestamp), GetType(DateTime))
    sourceTable.Columns.Add("Channel1", GetType(Double?))
    sourceTable.Columns.Add("Channel2", GetType(Double?))
    ' 添加其他通道列...

    For Each v In Me
        sourceTable.Rows.Add(v.Timestamp, v.Channel1, v.Channel2)
    Next

    ' 2. 创建转置后的DataTable结构
    Dim transposedTable As New DataTable()
    transposedTable.Columns.Add("ChannelName")
    ' 将所有时间戳作为转置后的列
    For Each row In sourceTable.Rows
        transposedTable.Columns.Add(row(NameOf(Voltage.Timestamp)).ToString(), GetType(Double?))
    Next

    ' 3. 填充转置数据
    For Each col In sourceTable.Columns.Cast(Of DataColumn)().Where(Function(c) c.ColumnName <> NameOf(Voltage.Timestamp))
        Dim newRow = transposedTable.NewRow()
        newRow("ChannelName") = col.ColumnName
        For i = 0 To sourceTable.Rows.Count - 1
            newRow(i + 1) = sourceTable.Rows(i)(col)
        Next
        transposedTable.Rows.Add(newRow)
    Next

    Return transposedTable
End Function

4. 手动循环遍历（最高性能） #

若数据量极大且对性能要求苛刻，直接手动循环遍历集合，避免LINQ/反射的额外开销：

Public Function Transpose() As List(Of ChannelVoltage)
    ' 初始化各通道的数值列表
    Dim channel1Vals As New List(Of (DateTime, Double?))()
    Dim channel2Vals As New List(Of (DateTime, Double?))()
    ' 初始化其他通道列表...

    ' 遍历原始数据填充各通道
    For Each v In Me
        channel1Vals.Add((v.Timestamp, v.Channel1))
        channel2Vals.Add((v.Timestamp, v.Channel2))
        ' 填充其他通道
    Next

    ' 组装转置结果
    Return New List(Of ChannelVoltage) From {
        New ChannelVoltage With {.ChannelName = "Channel1", .Values = channel1Vals},
        New ChannelVoltage With {.ChannelName = "Channel2", .Values = channel2Vals}
        ' 添加其他通道
    }
End Function

内容的提问来源于stack exchange，提问作者Paul Johnson