VB.NET - 創建從文件

Question

頭變量使用Visual Basic.NET 我有我已經證實

If My.Computer.FileSystem.FileExists(path + "\DATA") Then 
     MessageBox.Show("Files exist!") 
     End Using 
    Else 
     MessageBox.Show("Files missing!") 
    End If 

現在，我需要檢查的前四個字節的硬盤驅動器上的文件（頭文件）的DATA文件。他們應該是XMBF。我能從前四個字節創建一個變量嗎？

Dim header as string = 'Data's first four bytes 

我知道上面的代碼無法正常工作（明顯），但

Answer 1

這是一種方法（評論在線）：

Dim fSuccess As Boolean 
    Dim fileName As String 

    ' Use builtin method to combine two or more directory or file names; this will handle trailing \ correctly 
    fileName = IO.Path.Combine(path, "DATA") 

    ' Use standard io methods to see if the file exists 
    If IO.File.Exists(fileName) Then 
     ' Open the file for reading; this opens a FileStream 
     Using fs As IO.FileStream = IO.File.OpenRead(fileName) 
      ' Declare how much data you want to read 
      ' Note that you may need to change this to 8 if the file is expected to be encoded in unicode format 
      Const BYTES_TO_READ As Integer = 4 

      ' If the file is long enough, then read 
      If fs.Length >= BYTES_TO_READ Then 
       ' Setup the byte array that you are going to read the data into 
       Dim fileData(BYTES_TO_READ - 1) As Byte 

       ' Read the number of bytes into the local variable, double-checking to see if you read enough 
       If fs.Read(fileData, 0, BYTES_TO_READ) = BYTES_TO_READ Then 
        ' If the bytes that you read 
        If Convert.ToString(fileData).Equals("XMBF", StringComparison.InvariantCultureIgnoreCase) Then 
         fSuccess = True 
        End If 
       End If 
      End If 
     End Using 
    End If 

    If fSuccess Then 
     Debug.WriteLine("Success") 
    Else 
     Debug.WriteLine("Failure") 
    End If