如何在Winforms应用程序中从app.config加载连接字符串后保护内存中的连接字符串

using System;
using System.Configuration;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Cryptography;
using System.Text;

namespace WinformsApp
{
    public static class ConnectionStringHelper
    {
        public static SecureString GetProtectedConnectionString(string name)
        {
            // 获取连接字符串
            var connectionString = ConfigurationManager.ConnectionStrings[name]?.ConnectionString;
            if (string.IsNullOrEmpty(connectionString))
            {
                throw new Exception($"连接字符串 '{name}' 不存在或为空。");
            }

            // 加密连接字符串
            var encryptedString = ProtectString(connectionString);

            // 创建安全字符串
            var secureString = new SecureString();
            foreach (var c in encryptedString)
            {
                secureString.AppendChar(c);
            }
            secureString.MakeReadOnly();

            return secureString;
        }

        private static string ProtectString(string input)
        {
            // 将字符串转换为字节数组
            var bytes = Encoding.UTF8.GetBytes(input);

            // 使用DPAPI对字节数组进行加密
            var encryptedBytes = ProtectedData.Protect(bytes, null, DataProtectionScope.CurrentUser);

            // 将加密后的字节数组转换为Base64字符串
            var encryptedString = Convert.ToBase64String(encryptedBytes);

            return encryptedString;
        }

        private static string UnprotectString(string input)
        {
            // 将Base64字符串转换为字节数组
            var encryptedBytes = Convert.FromBase64String(input);

            // 使用DPAPI对字节数组进行解密
            var bytes = ProtectedData.Unprotect(encryptedBytes, null, DataProtectionScope.CurrentUser);

            // 将解密后的字节数组转换为字符串
            var decryptedString = Encoding.UTF8.GetString(bytes);

            return decryptedString;
        }
    }

    public class Program
    {
        public static void Main()
        {
            // 从app.config加载连接字符串并保护内存中的连接字符串
            var secureConnectionString = ConnectionStringHelper.GetProtectedConnectionString("MyConnectionString");

            // 在需要使用连接字符串的地方，可以使用SecureString进行操作
            // 例如，可以将SecureString转换为普通的字符串
            var connectionString = ConvertToUnsecureString(secureConnectionString);

            // 使用连接字符串进行数据库连接等操作
            // ...

            // 清除内存中的连接字符串
            secureConnectionString.Dispose();
        }

        private static string ConvertToUnsecureString(SecureString secureString)
        {
            // 将SecureString转换为普通的字符串
            var unsecureStringPtr = IntPtr.Zero;
            try
            {
                unsecureStringPtr = Marshal.SecureStringToGlobalAllocUnicode(secureString);
                return Marshal.PtrToStringUni(unsecureStringPtr);
            }
            finally
            {
                Marshal.ZeroFreeGlobalAllocUnicode(unsecureStringPtr);
            }
        }
    }
}