如果给我一个我知道已经被一个String填充的MemoryStream，我该如何退回一个String呢？

解决方案

回答

使用StreamReader，然后可以使用返回字符串的ReadToEnd方法。

回答

使用StreamReader将MemoryStream转换为字符串。

<Extension()> _
Public Function ReadAll(ByVal memStream As MemoryStream) As String
    ' Reset the stream otherwise you will just get an empty string.
    ' Remember the position so we can restore it later.
    Dim pos = memStream.Position
    memStream.Position = 0

    Dim reader As New StreamReader(memStream)
    Dim str = reader.ReadToEnd()

    ' Reset the position so that subsequent writes are correct.
    memStream.Position = pos

    Return str
End Function

回答

此示例说明如何向MemoryStream读取和写入字符串。

Imports System.IO

Module Module1
  Sub Main()
    ' We don't need to dispose any of the MemoryStream 
    ' because it is a managed object. However, just for 
    ' good practice, we'll close the MemoryStream.
    Using ms As New MemoryStream
      Dim sw As New StreamWriter(ms)
      sw.WriteLine("Hello World")
      ' The string is currently stored in the 
      ' StreamWriters buffer. Flushing the stream will 
      ' force the string into the MemoryStream.
      sw.Flush()
      ' If we dispose the StreamWriter now, it will close 
      ' the BaseStream (which is our MemoryStream) which 
      ' will prevent us from reading from our MemoryStream
      'sw.Dispose()

      ' The StreamReader will read from the current 
      ' position of the MemoryStream which is currently 
      ' set at the end of the string we just wrote to it. 
      ' We need to set the position to 0 in order to read 
      ' from the beginning.
      ms.Position = 0
      Dim sr As New StreamReader(ms)
      Dim myStr = sr.ReadToEnd()
      Console.WriteLine(myStr)

      ' We can dispose our StreamWriter and StreamReader 
      ' now, though this isn't necessary (they don't hold 
      ' any resources open on their own).
      sw.Dispose()
      sr.Dispose()
    End Using

    Console.WriteLine("Press any key to continue.")
    Console.ReadKey()
  End Sub
End Module

回答

我们也可以使用

Encoding.ASCII.GetString(ms.ToArray());

我认为这样做效率不高，但我不能对此宣誓。它还允许我们选择其他编码，而使用StreamReader则必须将其指定为参数。

回答

稍作修改的Brian答案允许对读开始进行可选管理，这似乎是最简单的方法。可能不是最有效的，但易于理解和使用。

Public Function ReadAll(ByVal memStream As MemoryStream, Optional ByVal startPos As Integer = 0) As String
    ' reset the stream or we'll get an empty string returned
    ' remember the position so we can restore it later
    Dim Pos = memStream.Position
    memStream.Position = startPos

    Dim reader As New StreamReader(memStream)
    Dim str = reader.ReadToEnd()

    ' reset the position so that subsequent writes are correct
    memStream.Position = Pos

    Return str
End Function