Microsoft .NET Framework三个流行版本 3.5、4.5.2、4.6.2的官方下载地址：
Microsoft .NET Framework 3.5：
https://download.microsoft.com/download/2/0/E/20E90413-712F-438C-988E-FDAA79A8AC3D/dotnetfx35.exe
Microsoft .NET Framework 4.5.2：
https://download.microsoft.com/download/E/2/1/E21644B5-2DF2-47C2-91BD-63C560427900/NDP452-KB2901907-x86-x64-AllOS-ENU.exe
Microsoft .NET Framework 4.6.2：
https://download.microsoft.com/download/F/9/4/F942F07D-F26F-4F30-B4E3-EBD54FABA377/NDP462-KB3151800-x86-x64-AllOS-ENU.exe
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Microsoft .NET Framework 各版本官方下载地址：
https://docs.microsoft.com/en-us/dotnet/framework/deployment/deployment-guide-for-developers
https://www.microsoft.com/en-us/download/developer-tools.aspx
