Visual Basic 如何读取 CSV 文件并在数据网格中显示值？

Posted 2023-02-22

【中文标题】Visual Basic 如何读取 CSV 文件并在数据网格中显示值？

【英文标题】：Visual Basic How do I read a CSV file and display the values in a datagrid?

【发布时间】：2010-11-05 00:24:03

【问题描述】：

我使用的是 VB 2005，如何打开 CSV 文件并读取列/行并在数据网格中显示值？

CSV 文件示例： jsmith,[e-mail]

然后我想对每一行（即每个用户）执行一个操作，我该怎么做？

如您所知，我是一个新手，但很高兴学习。

谢谢

【参考方案1】：

用法：

Dim reader As New Common.CSVReader("C:\MyFile.txt")
reader.DisplayResults(dgvMyView)

类：

Imports System.Windows.Forms
Imports System.IO
Imports System.Text.RegularExpressions

Public Class CSVReader
    Private Const ESCAPE_SPLIT_REGEX = "(1[^1]*1)*(?<Separator>0)(1[^1]*1)*"
    Private FieldNames As String()
    Private Records As List(Of String())
    Private ReadIndex As Integer 

    Public Sub New(File As String)
        Records = New List(Of String())
        Dim Record As String()
        Dim Reader As New StreamReader(File)
        Dim Index As Integer = 0
        Dim BlankRecord As Boolean = True 

        FieldNames = GetEscapedSVs(Reader.ReadLine())
        While Not Reader.EndOfStream
            Record = GetEscapedSVs(Reader.ReadLine())
            BlankRecord = True
            For Index = 0 to Record.Length - 1
                If Record(Index) <> "" Then BlankRecord = False 
            Next
            If Not BlankRecord Then Records.Add(Record)
        End While
        ReadIndex = -1
        Reader.Close()
    End Sub

    Private Function GetEscapedSVs(Data As String, Optional Separator As String = ",", Optional Escape As String = """") As String()
        Dim Result As String()      
        Dim Index As Integer
        Dim PriorMatchIndex As Integer = 0
        Dim Matches As MatchCollection = _
            Regex.Matches(Data, String.Format(ESCAPE_SPLIT_REGEX, Separator, Escape))

        ReDim Result(Matches.Count)

        For Index = 0 to Result.Length - 2
            Result(Index) = Data.Substring(PriorMatchIndex, Matches.Item(Index).Groups("Separator").Index - PriorMatchIndex)
            PriorMatchIndex = Matches.Item(Index).Groups("Separator").Index + Separator.Length
        Next
        Result(Result.Length - 1) = Data.Substring(PriorMatchIndex)

        For Index = 0 To Result.Length - 1
            If Regex.IsMatch(Result(Index), String.Format("^0[^0].*[^0]0$", Escape)) Then _
    Result(Index) = Result(Index).Substring(1, Result(Index).Length - 2)
            Result(Index) = Replace(Result(Index), Escape & Escape, Escape)
            If Result(Index) Is Nothing Then Result(Index) = ""
        Next

        GetEscapedSVs = Result 
    End Function

    Public ReadOnly Property FieldCount As Integer 
        Get
            Return FieldNames.Length 
        End Get
    End Property

    Public Function GetString(Index As Integer) As String
        Return Records(ReadIndex)(Index)
    End Function

    Public Function GetName(Index As Integer) As String
        Return FieldNames(Index)
    End Function

    Public Function Read() As Boolean
        ReadIndex = ReadIndex + 1
        Return ReadIndex < Records.Count 
    End Function


    Public Sub DisplayResults(DataView As DataGridView)
        Dim col As DataGridViewColumn
        Dim row As DataGridViewRow
        Dim cell As DataGridViewCell
        Dim header As DataGridViewColumnHeaderCell
        Dim Index As Integer
        ReadIndex = -1

        DataView.Rows.Clear()
        DataView.Columns.Clear()

        For Index = 0 to FieldCount - 1
            col = new DataGridViewColumn()
            col.CellTemplate = new DataGridViewTextBoxCell()
            header = new DataGridViewColumnHeaderCell()
            header.Value = GetName(Index)
            col.HeaderCell = header
            DataView.Columns.Add(col)
        Next 

        Do While Read()
            row = new DataGridViewRow()
            For Index = 0 to FieldCount - 1
                cell = new DataGridViewTextBoxCell()
                cell.Value = GetString(Index).ToString()
                row.Cells.Add(cell)
            Next
            DataView.Rows.Add(row)
        Loop
    End Sub
End Class

【讨论】：

相当多的代码。为什么不使用 VB.NET 中内置的 TextParser？ msdn.microsoft.com/en-us/library/…

由于 CSV 从未被严格定义，我觉得使用内置库将不可避免地导致黑盒综合症。有些事情不会正常工作，你不会知道为什么。我想这是一个偏好问题。

【参考方案2】：

这是一个使用 ADO.Net 的 ODBC 文本驱动程序的简单解决方案：

Dim csvFileFolder As String = "C:\YourFileFolder"
Dim csvFileName As String = "YourFile.csv"

'Note that the folder is specified in the connection string,
'not the file. That's specified in the SELECT query, later.
Dim connString As String = "Driver=Microsoft Text Driver (*.txt; *.csv);Dbq=" _
    & csvFileFolder & ";Extended Properties=""Text;HDR=No;FMT=Delimited"""

Dim conn As New Odbc.OdbcConnection(connString)

'Open a data adapter, specifying the file name to load
Dim da As New Odbc.OdbcDataAdapter("SELECT * FROM [" & csvFileName & "]", conn)
'Then fill a data table, which can be bound to a grid
Dim dt As New DataTable
da.Fill(dt)

grdCSVData.DataSource = dt

填充后，您可以对数据表的属性（如 ColumnName）进行赋值，以充分利用 ADO.Net 数据对象的所有功能。

在VS2008中你可以使用Linq来达到同样的效果。

【参考方案3】：

使用TextFieldParser 即built into VB.NET。谷歌找到了我this example

Using MyReader As New Microsoft.VisualBasic.FileIO.TextFieldParser _
  ("C:\test\info.csv")

  'Specify that reading from a comma-delimited file'
  MyReader.TextFieldType = FileIO.FieldType.Delimited
  MyReader.SetDelimiters(",")

  Dim currentRow As String()
  While Not MyReader.EndOfData
    Try
      currentRow = MyReader.ReadFields()
      With Me.dgvReport.Rows
        .Add(currentRow) 'Add new row to data grid view'
     End With
   Catch ex As Microsoft.VisualBasic.FileIO.MalformedLineException
     MsgBox("Line " & ex.Message & _
       "is not valid and will be skipped.")
   End Try
 End While
End Using

【讨论】：

投反对票的人愿意发表评论解释原因吗？

【参考方案4】：

使用图书馆为您阅读。

CsvHelper（我维护的一个库）可通过 NuGet 获得。

我对VB不熟悉，所以如果有人想把它改成VB，请做。不过，这只是几行代码。

var streamReader = // Create StreamReader to CSV file.
var csvReader = new CsvReader( streamReader );
var myObjects = csvReader.GetRecords<MyObject>();
// You can then databind the myObjects collection to a datagrid.
// If you don't want the whole file, you can read row by row.
var myObject = csvReader.GetRecord<MyObject>();