简单写了个c#连接西门子PLC的小程序来练习，源代码放在下面，可以看看


using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using S7.Net;

namespace 西门子连接上位机
{
    public partial class Form1 : Form
    {
        public Plc Myplc;
        public string IP = "192.168.1.118";//PLC的IP地址
        public void Connect()//创建连接PLC方法
        {
            try
            {
                Myplc = new Plc(CpuType.S71500, IP, 0, 1);//实例化PLC对象
            }
            catch { MessageBox.Show("连接失败！"); }
        }
        public Form1()
        {
            InitializeComponent();
            Connect();//调用连接PLC方法
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if(Myplc==null)
            {
                MessageBox.Show("连接失败！");
                return;
            }
            try
            {
                Myplc.Open();//打开PLC连接
                button1.BackColor = Color.Lime;//改变按钮1颜色为绿色
                button2.BackColor = Color.White;//改变按钮2颜色为白色
                button1.Text = "已连接PLC";//改变按钮1文字为已连接PLC
                label1.Text = "已连接到PLC";//改变label1文字为已连接到PLC
                label1.Visible = true;//显示label1
                
            }
            catch { MessageBox.Show("连接失败！"); }//捕获异常
            
        }

        private void button2_Click(object sender, EventArgs e)
        {
            if (Myplc == null)
            {
                MessageBox.Show("连接失败！");//判断PLC是否连接成功
                return;
            }
            try
            {
                Myplc.Close();//关闭PLC连接
                button2.BackColor = Color.Lime;//改变按钮2颜色为绿色
                button1.BackColor = Color.White;//改变按钮1颜色为白色
                button2.Text = "已断开PLC";//改变按钮2文字为已断开PLC
                label1.Visible = false;//隐藏label1
            }
            catch { MessageBox.Show("断开失败！"); }//捕获异常
            
        }

        private void button3_Click(object sender, EventArgs e)
        {
            if (Myplc == null)
            {
                MessageBox.Show("连接失败！");//判断PLC是否连接成功
                return;
            }
            try
            {
                if ((bool)Myplc.Read("DB1.DBX0.0") == false)//判断读取的BOOL变量对按钮进行取反操作
                {
                    Myplc.Write("DB1.DBX0.0", 1);//写入BOOL变量
                    button3.BackColor = Color.Lime;//改变按钮3颜色为绿色
                }
                else if ((bool)Myplc.Read("DB1.DBX0.0") == true)
                {
                    Myplc.Write("DB1.DBX0.0", 0);//写入BOOL变量
                    button3.BackColor = Color.White;//改变按钮3颜色为白色
                }
                else { MessageBox.Show("读取或写入失败！"); }//捕获异常
            }
            catch { MessageBox.Show("读取或写入失败！"); }//捕获异常
            
            
        }
    }
}