Question

我试图在VB中使用循环填充数组。它基本上读取.txt文件并将所有行存储在一个数组中。我得到这个错误。 “在分配值之前使用数组”。

Dim fileEntries As String() = Directory.GetFiles(folderDIR, "*.txt")
Dim fileName As String
Dim fileReader As StreamReader
Dim strReadFile As String
Dim arrLines() As String
Dim i As Integer = 0
For Each fileName In fileEntries
    fileReader = File.OpenText(fileName)
    Do Until fileReader.Peek = -1
        strReadFile = fileReader.ReadLine()
        arrLines(i) = strReadFile
        i += 1
    Loop
Next

有没有办法在不预先定义数组长度的情况下做到这一点？我希望数组的长度是txt文件中的行数。希望我解释得很好。提前谢谢。

Answer 1

有很长一段时间，在vb6中，我使用 ReDim 在循环中动态地在数组中添加一个新条目。不方便：减慢过程。最好在创建数组之前计算文件所需的出现次数。希望有所帮助。

Answer 2

你可以将arrlines声明为list：

Dim arrLines As New List(Of String)()

然后你可以转换为arrLines到array：

arrLines.ToArray()

试试这个：

Dim fileEntries As String() = Directory.GetFiles(folderDIR, "*.txt")
Dim fileName As String
Dim fileReader As StreamReader
Dim strReadFile As String
Dim arrLines As New List(Of String)()
Dim i As Integer = 0
For Each fileName In fileEntries
    fileReader = File.OpenText(fileName)
    Do Until fileReader.Peek = -1
        strReadFile = fileReader.ReadLine()
        arrLines.Add(strReadFile)
    Loop
Next
arrLines.ToArray()

Answer 3

您可以这样做：

Dim fileEntries As String() = Directory.GetFiles(folderDIR, "*.txt")
Dim fileName As String
Dim fileReader As StreamReader
Dim strReadFile As String
Dim arrLines() As String = {} 'Added this
'Dim i As Integer = 0 'Removed this
For Each fileName In fileEntries
    fileReader = File.OpenText(fileName)
    Do Until fileReader.Peek = -1
        strReadFile = fileReader.ReadLine()
        If arrLines.Length = 0 Then ReDim arrLines(0 To 0) Else ReDim Preserve arrLines(0 To arrLines.Length)
        arrLines(arrLines.Length - 1) = strReadFile
        i += 1
    Loop
Next

或者......

如何在vb中赋值之前使用数组

3 个答案: