使用streamreader将文件加载到数组中答案

【问题标题】：Loading file into array using streamreader使用streamreader将文件加载到数组中
【发布时间】：2016-01-13 23:16:08
【问题描述】：

我正在尝试获取一个文件并使用 StreamReader 对其进行迭代并将每一行加载到一个数组中。我知道文件输入正确，它是一个数据文本文件。

    Dim req As WebRequest = WebRequest.Create("http://www.blahahahaha.com/data/myfile.csv")
    Dim res As WebResponse = req.GetResponse()
    Dim stream As Stream = res.GetResponseStream()

    Dim lines2 As String()
    Using r As StreamReader = New StreamReader(stream, Encoding.ASCII)
        Dim line As String
        line = r.ReadLine
        Do While (Not line Is Nothing)
            lines2(lineCount2) = r.ReadLine
            lineCount2 += 1
        Loop
    End Using

但是结果数组是空的。我做错了什么，我该如何解决？

【问题讨论】：

你永远不会初始化数组。将其更改为 List(of String)，因为您不知道会有多少行。我应该认为这会引发异常。我也将 Nothing 测试更改为 String.IsNullOrEmpty()
你能用代码显示吗？

标签： arrays vb.net streamreader

【解决方案1】：

这一行：

Dim lines2 As String()

只需声明lines2 将是一个字符串数组。数组本身未初始化：

Dim lines2(9) As String     ' THIS one has elements

但由于您可能不知道会有多少行，请使用列表：

Dim Lines As New List(Of String)

Using r As StreamReader = New StreamReader(Stream, Encoding.ASCII)
    Dim line As String
    line = r.ReadLine
    Do Until String.IsNullOrEmpty(line)
        Lines.Add(line)
        line = r.ReadLine
    Loop
End Using

如果调用代码真的需要一个数组：

Return Lines.ToArray()

【讨论】：

【解决方案2】：

这将返回 6 行作为字符串数组，第一行是列名

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim csvAddress As String =
        "https://download.microsoft.com/download/4/C/8/4C830C0C-101F-4BF2-8FCB-32D9A8BA906A/Import_User_Sample_en.csv"

    Dim Lines As String() = GetCsvData(csvAddress)
    For Each line As String In Lines
        Console.WriteLine(line)
    Next
End Sub
Public Function GetCsvData(ByVal csvAddress As String) As String()
    Dim request As WebRequest = WebRequest.Create(csvAddress)
    request.Credentials = CredentialCache.DefaultCredentials
    Dim response As WebResponse = request.GetResponse()

    Dim dataStream As Stream = response.GetResponseStream()
    Dim LineList As New List(Of String)

    Using r As StreamReader = New StreamReader(dataStream, Encoding.ASCII)
        Dim currentLine As String = r.ReadLine
        Do While (Not String.IsNullOrWhiteSpace(currentLine))
            LineList.Add(currentLine)
            currentLine = r.ReadLine
        Loop
    End Using

    Return LineList.ToArray

End Function

【讨论】：