参考资料:
# 已在此计算机上安装相同或更高版本的 .NET Framework #
https://blog.csdn.net/qianxing111/article/details/79003298
https://blog.csdn.net/wangzl1163/article/details/78481894/
# .NET Framework 各版本介绍和下载链接汇总 #
https://blog.csdn.net/my98800/article/details/50901911