C#窗体程序，创建串口的接收和发送，先检查串口的连接状态，如果已经连接好则向com1发送A0 EC B6 E3数据，等待5秒后再向com2发送play数据,再等待5后再向com3发送1234数据并且所有端口只发送一次的完整代码

在C#中创建一个简单的Windows Form应用程序，用于控制串口通信，你可以使用`System.IO.Ports.SerialPort`类。首先需要添加对`System.IO.Ports命名空间`的引用。以下是完整的代码示例：

using System;
using System.IO.Ports;

public partial class MainForm : Form
{
    SerialPort serialPort1, serialPort2, serialPort3;
    
    public MainForm()
    {
        InitializeComponent();
        InitializeSerialPorts();
    }

    private void InitializeSerialPorts()
    {
        // 检查并设置串口连接
        serialPort1 = new SerialPort("COM1");
        serialPort1.DataReceived += SerialPort_DataReceived;
        if (serialPort1.IsOpen)
            SendDataToCom1();

        serialPort2 = new SerialPort("COM2");
        serialPort2.DataReceived += SerialPort_DataReceived;
        
        serialPort3 = new SerialPort("COM3");
        serialPort3.DataReceived += SerialPort_DataReceived;
    }

    private void SerialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        Console.WriteLine("Data received on " + ((SerialPort)sender).Name);
    }

    private void SendDataToCom1()
    {
        byte[] data = { 0x41, 0x30, 0xEC, 0xB6, 0xE3 };
        try
        {
            serialPort1.Write(data, 0, data.Length);
            Console.WriteLine("Sent data to COM1: A0 EC B6 E3");
            Thread.Sleep(5000); // 等待5秒
        }
        catch (Exception ex)
        {
            Console.WriteLine("Error sending to COM1: " + ex.Message);
        }
        finally
        {
            if (!serialPort1.IsDisposed)
                serialPort1.Close(); // 关闭连接后不再发送
        }
    }

    private void SendPlayDataToCom2()
    {
        string playData = "play";
        try
        {
            serialPort2.Write(playData, 0, playData.Length);
            Console.WriteLine($"Sent '{playData}' to COM2");
            Thread.Sleep(5000); // 再次等待5秒
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error sending to COM2: {ex.Message}");
        }
    }

    private void SendDataToCom3()
    {
        int num = 1234;
        try
        {
            serialPort3.Write(BitConverter.GetBytes(num), 0, sizeof(int));
            Console.WriteLine($"Sent number {num} to COM3");
            Thread.Sleep(5000); // 最后一次等待5秒
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error sending to COM3: {ex.Message}");
        }
    }

    private void buttonSend_Click(object sender, EventArgs e)
    {
        SendDataToCom1();
        SendPlayDataToCom2();
        SendDataToCom3();
    }
}

在这个代码中，我们初始化了三个串口，并在单击按钮时依次发送数据。注意这只是一个基本示例，实际应用可能需要处理异常、超时和其他更复杂的场景。