如何从datagridview导出csv仅在VB.Net中可见列?

Question

我正在研究抓取程序，从我的程序中抓取项目后的下一步是从datagridview生成/导出到csv文件。我已经做了如下的保存代码，但我只想导出一个可见的列。我怎么能那样做呢?

Private Sub CmdCSV_Click(sender As Object, e As EventArgs) Handles CmdCSV.Click
Dim sfd As New SaveFileDialog()
sfd.FileName = "export-csv"
sfd.Filter = "CSV File | *.csv"
If sfd.ShowDialog() = DialogResult.OK Then
Using sw As StreamWriter = File.CreateText(sfd.FileName)
Dim dgvColumnNames As List(Of String) = DataGridView1.Columns.Cast(Of DataGridViewColumn).ToList().Select(Function(c) c.Name).ToList()
sw.WriteLine(String.Join(";", dgvColumnNames))
For Each row As DataGridViewRow In DataGridView1.Rows
Dim rowData As New List(Of String)
For Each column As DataGridViewColumn In DataGridView1.Columns
rowData.Add(Convert.ToString(row.Cells(column.Name).Value))
Next
sw.WriteLine(String.Join(";", rowData))
Next
End Using
End If
End Sub

Answer 1

首先，这里没有必要调用两次ToList:

Dim dgvColumnNames As List(Of String) = DataGridView1.Columns.Cast(Of DataGridViewColumn).ToList().Select(Function(c) c.Name).ToList()

你不需要一个通用的List来做Select，所以删除第一个ToList:

Dim dgvColumnNames = DataGridView1.Columns.
Cast(Of DataGridViewColumn).
Select(Function(c) c.Name).
ToList()

如果您想过滤该列表以只包含可见列，那么您就可以这样做。Where方法是如何过滤的:

Dim dgvColumnNames = DataGridView1.Columns.
Cast(Of DataGridViewColumn).
Where(Function(c) c.Visible).
Select(Function(c) c.Name).
ToList()

你也应该替换这个:

Dim rowData As New List(Of String)
For Each column As DataGridViewColumn In DataGridView1.Columns
rowData.Add(Convert.ToString(row.Cells(column.Name).Value))
Next

与这个:

Dim rowData As New List(Of String)
For Each columnName In dgvColumnNames
rowData.Add(Convert.ToString(row.Cells(columnName).Value))
Next

，或者更简单地说:

Dim rowData = dgvColumnNames.Select(Function(s) row.Cells(columnName).Value.ToString()).ToList()

最后一个ToList也不需要，因为String.Join接受IEnumerable(Of String)。除非您确实需要，否则不要花费额外的时间和精力将内容转换为通用的List。