vb.net - 如何将文件复制/替换到 VB.NET 中的文件夹中？

Question

我用File.Copy(source, target, True), wheresource是全路径名，比如c:\source.txtandtarget是一个文件夹，里面可能包含同名文件。如果文件已经存在，我想复制source.txt到目标文件夹并覆盖。

但我得到了错误：

'目标是一个文件夹，而不是一个文件'

Answer 1

目标也必须包含一个文件名：

sSource = "C:\something.txt"
sTarget = "C:\folder\something.txt"

File.Copy(sSource, sTarget, True)

如果您想以编程方式拥有相同的文件名，只需执行以下操作：

File.Copy(sSource, Path.Combine(sFolder, Path.GetFileName(sSource)), True)

阅读MSDN 文档以获取有关异常和方法使用的示例和信息。

Answer 2

您还可以使用 FileStream 来读取和写入文件内容。如果您使用文件流，您可以读取和写入所有类型的二进制文件，而不仅仅是文本文件。

使用以下过程：

''' <summary>
    ''' copies a file from one location to another
    ''' </summary>
    ''' <param name="inputPath">full path to the input file</param>
    ''' <param name="outputPath">full path to the output file</param>
    ''' <param name="bufferSize">the size in bytes as an integer that will be read and written at a time from input file and to the output file</param>
    ''' <param name="overwrite">overwrite the output file if it already exists</param>
    ''' <returns></returns>
    Public Function CopyFile(ByVal inputPath As String,
                             ByVal outputPath As String,
                             ByVal bufferSize As Integer,
                             Optional ByVal overwrite As Boolean = False) As Boolean

        Dim PathIsClear As Boolean = True, SucOpt As Boolean = False
        Dim inputByteReaderObj As System.IO.FileStream = System.IO.File.Open(inputPath, IO.FileMode.Open) 'open a file stream for reading bytes from the input file
        Dim endofSize As Integer = My.Computer.FileSystem.GetFileInfo(inputPath).Length
        If overwrite AndAlso FileExists(outputPath) Then
            'if file exits, delete the output file
            PathIsClear = False
            PathIsClear = DeleteFilesOnDisk(outputPath) ' Delete the output file if it already exists
        End If

        ' Adjust array length for VB array declaration.

        Dim allBytesRead As Integer = 0, sucessfullBytes As Integer = 0, bytes As Byte() 'The byte array
        If bufferSize > endofSize Then
            bufferSize = endofSize
        End If
        If bufferSize >= 1 Then
            bytes = New Byte(bufferSize - 1) {} 'The byte array; create a byte array that will hold the data in length equal to the bufferSize; the array index starts at 0;
            If PathIsClear Then
                While inputByteReaderObj.Read(bytes, 0, bufferSize) > 0
                    'read bytes consequtively from the input file, each time read bytes equal in length to bufferSize
                    Try
                        My.Computer.FileSystem.WriteAllBytes(outputPath, bytes, True) ' Append to the file contents
                        sucessfullBytes += bufferSize
                    Catch ex As Exception
                        Stop
                    End Try
                    allBytesRead += bufferSize
                    If (allBytesRead + bufferSize) > endofSize Then
                        bufferSize = endofSize - allBytesRead 'change the size of the buffer match the end of the file
                    End If
                    If bufferSize >= 1 Then
                        bytes = New Byte(bufferSize - 1) {} 'the array index starts at zero, the bufferSize starts at 1
                    End If
                    If allBytesRead >= endofSize Or bufferSize = 0 Then
                        'the reader has already reached the end of file, exit the reader loop
                        Exit While
                    End If
                End While
                If sucessfullBytes = allBytesRead Then
                    SucOpt = True
                End If
            End If
        Else
            'write an empty file
            Try
                System.IO.File.Create(outputPath) 'Create an empty file because the size of the input file is zero
            Catch ex As Exception
                'an error occured in creating an empty file
            End Try
        End If

        inputByteReaderObj.Close()

        Return SucOpt
    End Function