vb.net - 将字符串发送到其等效的十六进制值

Question

我想向我的设备发送 hex 命令，因为它只能理解 hex 。

因此，我设法创建一个函数，可以验证用户输入的 string 是否具有有效对应的 hex 。问题是 here 。

因此，通过验证 users input 是否具有相应的 hex 等效项，我确信我的系统发送的内容将被我的设备读取。 By searching 我意识到它需要转换为字节，它指出

Use the ASCIIEncoding class to convtert strings to an array of bytes you can transmit.

Code:

Dim str as String = "12345678"
Dim bytes() as Byte = ASCIIEncoding.ASCII.GetBytes(strNumbers)
' Then Send te bytes to the reader
sp.Write(bytes, 0, bytes.Length)

You do not need to covert the values to HEX, in this case HEX is mearly a different way of displaying the same thing.

我的代码:

'This is a string with corresponding hex value
Dim msg_cmd as string  = "A0038204D7" 
'Convert it to byte so my device can read it
Dim process_CMD() As Byte = ASCIIEncoding.ASCII.GetBytes(msg_cmd) 
'Send it as bytes
ComPort.Write(process_CMD, 0, process_CMD.Length) 

我的输出:

41 30 30 33 38 32 30 34 44 37

期望的输出:

A0 03 82 04 D7

Answer 1

要发送特定的字节序列，不要发送字符串 - 只需发送字节:

Dim process_CMD() As Byte = { &HA0, &H03, &H82, &H04, &HD7 }
ComPort.Write(process_CMD, 0, process_CMD.Length)

正如我在上面的评论中提到的，这些值只是数值。十六进制没有什么特别的。十六进制只是表示相同值的另一种方式。换句话说，上面的代码所做的事情与以下完全相同:

Dim process_CMD() As Byte = { 160, 3, 130, 4, 215 }
ComPort.Write(process_CMD, 0, process_CMD.Length)

如果字符串中有十六进制数字，则可以使用 appropriate overload 将十六进制数字的字符串表示形式转换为字节值。 Convert.ToByte 方法的。但是，一次只能转换一个字节，因此，首先您需要将字符串拆分为字节(每个字节两个十六进制数字。例如:

Dim input As String = "A0038204D7"
Dim bytes As New List(Of Byte)()
For i As Integer = 0 to input.Length Step 2
    bytes.Add(Convert.ToByte(input.SubString(i, 2), 16)
Next
Dim process_CMD() As Byte = bytes.ToArray()
ComPort.Write(process_CMD, 0, process_CMD.Length)

但是，如果字符串的字节之间有空格，则会更容易。然后你可以使用 String.Split 方法:

Dim input As String = "A0 03 82 04 D7"
Dim hexBytes As String() = input.Split(" "c)
Dim bytes As New List(Of Byte)()
For Each hexByte As String in hexBytes
    bytes.Add(Convert.ToByte(hexByte, 16)
Next
Dim process_CMD() As Byte = bytes.ToArray()
ComPort.Write(process_CMD, 0, process_CMD.Length)

或者，更简单地说:

Dim input As String = "A0 03 82 04 D7"
Dim process_CMD() As Byte = input.Split(" "c).Select(Function(x) Convert.ToByte(x, 16)).ToArray()
ComPort.Write(process_CMD, 0, process_CMD.Length)