C# 設置系統環境變量

using Microsoft.Win32;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Drawing;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;

namespace WindowsForms設置系統變量
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {


            //var str =  SysEnvironment.GetSysEnvironmentByName("Path"); //系統變量 Path
            //  SysEnvironment.SetSysEnvironment("Path", "0");
            //HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\Environment 下的Path值
            SysEnvironment.SetPathAfter(@"C:\mysql\bin");
            MessageBox.Show("完成!" + @"C:\mysql\bin;");
            var str = SysEnvironment.GetSysEnvironmentByName("Path"); //系統變量 Path
            string[] temp = str.Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries);
            for (int i = 0; i < temp.Length; i++)
            {
                textBox1.Text += temp[i] + "\r\n";
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            ////RunCmd(@"C:\Windows\System32\","ipconfig");
            //System.Diagnostics.Process.Start(@"C:\Windows\System32\cmd.exe");
            //textBox2.Text += Cmd(@"CD C:\mysql  mysqld --defaults-file=my.ini --initialize-insecure");

        }
        ///<summary>
        /// cmd命令執行，在cmd上可以執行的語句，直接傳到這里，調用grads畫圖實例如下：
        ///  Cmd("C:/OpenGrADS/Contents/Cygwin/Versions/2.0.1.oga.1/i686/grads.exe -lbcx 'D:/data_wrfchem/gs/d01_hour_pm25.gs D:/data_wrfchem 2016-04-18 d01'");
        ///  Cmd("grads啟動程序exe路徑 -lbcx 'gs腳本文件 參數1 參數2 參數3'");
        /// </summary>
        /// <param name="c">執行語句</param>
        public string Cmd(string c)
        {
            System.Diagnostics.Process process = new System.Diagnostics.Process();
            process.StartInfo.FileName = "cmd.exe";
            process.StartInfo.UseShellExecute = false;
            process.StartInfo.CreateNoWindow = true;
            process.StartInfo.RedirectStandardOutput = true;
            process.StartInfo.RedirectStandardInput = true;
            process.Start();
            process.StandardInput.WriteLine(c);
            process.StandardInput.AutoFlush = true;
            process.StandardInput.WriteLine("exit");
            StreamReader reader = process.StandardOutput;//截取輸出流
            //string output = reader.ReadLine();//每次讀取一行
            //while (!reader.EndOfStream)
            //{
            //    // PrintThrendInfo(output);
            //    output = reader.ReadLine();
            //}
            string output = reader.ReadToEnd();//每次讀取一行
            process.WaitForExit();

            return output;
        }
    }


    public static class SysEnvironment
    {


        #region --獲取注冊表中的環境變量

        /// <summary>
        /// 獲取系統環境變量
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        public static string GetSysEnvironmentByName(string name)
        {
            string result = string.Empty;
            try
            {
                result = OpenSysEnvironment().GetValue(name).ToString();//讀取
            }
            catch (Exception)
            {

                return string.Empty;
            }
            return result;

        }

        /// <summary>
        /// 打開系統環境變量注冊表
        /// </summary>
        /// <returns>RegistryKey</returns>
        private static RegistryKey OpenSysEnvironment()
        {
            RegistryKey regLocalMachine = Registry.LocalMachine;
            RegistryKey regSYSTEM = regLocalMachine.OpenSubKey("SYSTEM", true);//打開HKEY_LOCAL_MACHINE下的SYSTEM 
            RegistryKey regControlSet001 = regSYSTEM.OpenSubKey("ControlSet001", true);//打開ControlSet001 
            RegistryKey regControl = regControlSet001.OpenSubKey("Control", true);//打開Control 
            RegistryKey regManager = regControl.OpenSubKey("Session Manager", true);//打開Control 

            RegistryKey regEnvironment = regManager.OpenSubKey("Environment", true);
            return regEnvironment;
        }

        /// <summary>
        /// 設置系統環境變量
        /// </summary>
        /// <param name="name">變量名</param>
        /// <param name="strValue">值</param>
        public static void SetSysEnvironment(string name, string strValue)
        {
            OpenSysEnvironment().SetValue(name, strValue);
        }
        #endregion


        /// <summary>
        /// 檢測系統環境變量是否存在
        /// </summary>
        /// <param name="name"></param>
        /// <returns></returns>
        public static bool CheckSysEnvironmentExist(string name)
        {
            if (!string.IsNullOrEmpty(GetSysEnvironmentByName(name)))
                return true;
            else
                return false;
        }

        /// <summary>
        /// 添加到PATH環境變量（會檢測路徑是否存在，存在就不重復）
        /// </summary>
        /// <param name="strPath"></param>
        public static void SetPathAfter(string strHome)
        {
            string pathlist;
            pathlist = GetSysEnvironmentByName("PATH");

            bool isPathExist = false;
            if (pathlist.Length > 1)
            {
                //檢測是否以;結尾
                if (pathlist.Substring(pathlist.Length - 1, 1) != ";") //截取最后一個字符,判斷這個字符不等於;號,
                {
                    SetSysEnvironment("PATH", pathlist + ";");
                    pathlist = GetSysEnvironmentByName("PATH");
                }
                string[] list = pathlist.Split(';');//以;切割


                foreach (string item in list)
                {
                    if (item == strHome)
                        isPathExist = true;
                }
            }
            if (!isPathExist)
            {
                SetSysEnvironment("PATH", pathlist + strHome + ";");
            }
        }

        public static void SetPathBefore(string strHome)
        {

            string pathlist;
            pathlist = GetSysEnvironmentByName("PATH");
            string[] list = pathlist.Split(';');
            bool isPathExist = false;

            foreach (string item in list)
            {
                if (item == strHome)
                    isPathExist = true;
            }
            if (!isPathExist)
            {
                SetSysEnvironment("PATH", strHome + ";" + pathlist);
            }

        }

        public static void SetPath(string strHome)
        {
            string pathlist;
            pathlist = GetSysEnvironmentByName("PATH");
            string[] list = pathlist.Split(';');
            bool isPathExist = false;

            foreach (string item in list)
            {
                if (item == strHome)
                    isPathExist = true;
            }
            if (!isPathExist)
            {
                SetSysEnvironment("PATH", pathlist + strHome + ";");
            }
        }
    }

    //Kernel32.DLL內有SetEnvironmentVariable函數用於設置系統環境變量
    //C#調用要用DllImport，代碼封裝如下：
    class SetSysEnvironmentVariable
    {
        [DllImport("Kernel32.DLL ", SetLastError = true)]
        public static extern bool SetEnvironmentVariable(string lpName, string lpValue);

        public static void SetPath(string pathValue)
        {
            string pathlist;
            pathlist = SysEnvironment.GetSysEnvironmentByName("PATH");
            string[] list = pathlist.Split(';');
            bool isPathExist = false;

            foreach (string item in list)
            {
                if (item == pathValue)
                    isPathExist = true;
            }
            if (!isPathExist)
            {
                SetEnvironmentVariable("PATH", pathlist + pathValue + ";");

            }

        }
    }


}