VB.NET serialport收发数据时，影响按钮操作，迟钝，求解答

VB.NET VS2019, serialport收发数据，典型的代码，每200ms发一下命令，读取外部一个板子的数据。连接串口后，可以读到数据，但是此时点击‘关闭串口’，或者退出窗口，都要点很多次，才有效，好像收数据时，影响了其次按钮的执行一样，求解，，

Imports System
Imports System.IO.Ports
Public Class Form1

Dim PortSwitch As Boolean    '定义串口是否打开标志
Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)

Private Sub ComLoad()   '显示可以用的串口号
    Dim com_ports As String() = IO.Ports.SerialPort.GetPortNames
    'Dim i As Integer
    'i = 0
    For Each com_port As String In com_ports
        ComboBox_COM.Items.Add(com_port)
        'If i = 0 Then                 '让框里面显示第一个读到的COM口
        '    ComboBox_COM.Text = com_port
        '    i = i + 1
        'End If

    Next
    ComboBox_COM.SelectedIndex = 0
End Sub

Private Sub InitialPort(SerialPort As String, BaudRate As String)
    If SerialPort1.IsOpen = False Then   '只能再关闭串口的时候，修改串口的参数，否则报错
        SerialPort1.PortName = SerialPort  '串口名称
        SerialPort1.BaudRate = BaudRate '波特率
        SerialPort1.DataBits = 8 '数据位
        SerialPort1.StopBits = IO.Ports.StopBits.One '停止位
        SerialPort1.Parity = IO.Ports.Parity.None '校验位
    End If
End Sub





Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load


    ToolStripStatusLabel_Bottom.Text = ""
    ComLoad()
    Timer1.Interval = 200   '100ms




End Sub

Private Sub Button_About_Click(sender As Object, e As EventArgs) Handles Button_About.Click
    About.ShowDialog()
End Sub

Private Sub Button_Exit_Click(sender As Object, e As EventArgs) Handles Button_Exit.Click
    'MyBase.Close()
    Me.Dispose()
End Sub

Private Sub Button_OpenCloseCom_Click(sender As Object, e As EventArgs) Handles Button_OpenCloseCom.Click
    InitialPort(ComboBox_COM.Text, ComboBox_Baudrate.Text)

    If PortSwitch = False Then   '如果串口关闭
        Try
            SerialPort1.Open() '打开串口
            If SerialPort1.IsOpen = True Then
                PortSwitch = True         '则将串口打开标志设为允许打开
                Button_OpenCloseCom.Text = "关闭串口"
                ToolStripStatusLabel_Bottom.Text = "串口已连接"
                'ToolStripStatusLabel_Bottom.BackColor = Color.Green
                Timer1.Start()

            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message + "a")
        End Try
    Else

        Try

            Timer1.Stop()
            SerialPort1.Close() '关闭串口
            Sleep(1000)
            If SerialPort1.IsOpen = False Then
                PortSwitch = False        '否则将串口打开标志设为禁止打开
                Button_OpenCloseCom.Text = "打开串口"
                ToolStripStatusLabel_Bottom.Text = "串口未连接"
                'ToolStripStatusLabel_Bottom.BackColor = DefaultBackColor
            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message + "b")
        End Try
    End If
End Sub
Private Sub SendData(ByVal strdata As String)
    Try
        SerialPort1.Write(strdata)
        StatusLabel_SendcharNum.Text = Str(Val(StatusLabel_SendcharNum.Text) + SerialPort1.BytesToWrite)
    Catch ex As Exception
        MessageBox.Show(ex.Message)
    End Try
End Sub

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
    '每1000ms发送一次测试连通包，回应后，发送状态信息，如果未得到回应，则直接退出
    'If mode = "发送端" Then
    If PortSwitch = True Then
        If SerialPort1.IsOpen = True Then
            SendData("GD" & vbCrLf)
        End If
    End If

    'End If
    '每两秒查询一次数据库的状态，比对视频会议的时间，如果当前时间已经超过开会时间，则直接退出
End Sub




Private Sub Sp_Receiving(ByVal sender As Object, ByVal e As EventArgs)
    Dim strIncoming As String

    Try
        StatusLabel_ReceiveCharNum.Text = Str(Val(StatusLabel_ReceiveCharNum.Text) + SerialPort1.BytesToRead) '获取接收缓冲区中数据的字节数。
        strIncoming = SerialPort1.ReadExisting.ToString '读取缓冲区中的数据
        SerialPort1.DiscardInBuffer()
        Threading.Thread.Sleep(100) '线程的延时
        TextBox_Receive.Text = TextBox_Receive.Text + strIncoming



        TextBox_Receive.Focus()
        TextBox_Receive.SelectionLength = 0
        TextBox_Receive.SelectionStart = TextBox_Receive.Text.Length
        TextBox_Receive.ScrollToCaret()


    Catch ex As Exception
        MessageBox.Show(ex.Message)
    End Try
End Sub

Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
    Me.Invoke(New EventHandler(AddressOf Sp_Receiving)) '开启一个新的线程，运行接收数据的函数。
End Sub

End Class

Threading.Thread.Sleep(100) 这句会阻塞UI，要么多线程，要么采用异步

Threading.Thread.Sleep(100)
修改为
Threading.Thread.Sleep(10)
Application.DoEvents()