Inno安装程序：验证是否已安装.NET 4.0

运行Inno Setup可执行文件时，将调用 InitializeSetup 函数。为自定义脚本插入此代码应该可以完成您想要的操作：

The InitializeSetup function is called when the Inno Setup executable is run. Inserting this code for a custom script should do what you want:

function IsDotNetDetected(version: string; service: cardinal): boolean;
// Indicates whether the specified version and service pack of the .NET Framework is installed.
//
// version -- Specify one of these strings for the required .NET Framework version:
//    'v1.1'          .NET Framework 1.1
//    'v2.0'          .NET Framework 2.0
//    'v3.0'          .NET Framework 3.0
//    'v3.5'          .NET Framework 3.5
//    'v4\Client'     .NET Framework 4.0 Client Profile
//    'v4\Full'       .NET Framework 4.0 Full Installation
//    'v4.5'          .NET Framework 4.5
//    'v4.5.1'        .NET Framework 4.5.1
//    'v4.5.2'        .NET Framework 4.5.2
//    'v4.6'          .NET Framework 4.6
//    'v4.6.1'        .NET Framework 4.6.1
//    'v4.6.2'        .NET Framework 4.6.2
//    'v4.7'          .NET Framework 4.7
//
// service -- Specify any non-negative integer for the required service pack level:
//    0               No service packs required
//    1, 2, etc.      Service pack 1, 2, etc. required
var
    key, versionKey: string;
    install, release, serviceCount, versionRelease: cardinal;
    success: boolean;
begin
    versionKey := version;
    versionRelease := 0;

    // .NET 1.1 and 2.0 embed release number in version key
    if version = 'v1.1' then begin
        versionKey := 'v1.1.4322';
    end else if version = 'v2.0' then begin
        versionKey := 'v2.0.50727';
    end

    // .NET 4.5 and newer install as update to .NET 4.0 Full
    else if Pos('v4.', version) = 1 then begin
        versionKey := 'v4\Full';
        case version of
          'v4.5':   versionRelease := 378389;
          'v4.5.1': versionRelease := 378675; // 378758 on Windows 8 and older
          'v4.5.2': versionRelease := 379893;
          'v4.6':   versionRelease := 393295; // 393297 on Windows 8.1 and older
          'v4.6.1': versionRelease := 394254; // 394271 before Win10 November Update
          'v4.6.2': versionRelease := 394802; // 394806 before Win10 Anniversary Update
          'v4.7':   versionRelease := 460798; // 460805 before Win10 Creators Update
        end;
    end;

    // installation key group for all .NET versions
    key := 'SOFTWARE\Microsoft\NET Framework Setup\NDP\' + versionKey;

    // .NET 3.0 uses value InstallSuccess in subkey Setup
    if Pos('v3.0', version) = 1 then begin
        success := RegQueryDWordValue(HKLM, key + '\Setup', 'InstallSuccess', install);
    end else begin
        success := RegQueryDWordValue(HKLM, key, 'Install', install);
    end;

    // .NET 4.0 and newer use value Servicing instead of SP
    if Pos('v4', version) = 1 then begin
        success := success and RegQueryDWordValue(HKLM, key, 'Servicing', serviceCount);
    end else begin
        success := success and RegQueryDWordValue(HKLM, key, 'SP', serviceCount);
    end;

    // .NET 4.5 and newer use additional value Release
    if versionRelease > 0 then begin
        success := success and RegQueryDWordValue(HKLM, key, 'Release', release);
        success := success and (release >= versionRelease);
    end;

    result := success and (install = 1) and (serviceCount >= service);
end;


function InitializeSetup(): Boolean;
begin
    if not IsDotNetDetected('v4.6', 0) then begin
        MsgBox('MyApp requires Microsoft .NET Framework 4.6.'#13#13
            'Please use Windows Update to install this version,'#13
            'and then re-run the MyApp setup program.', mbInformation, MB_OK);
        result := false;
    end else
        result := true;
end;

（代码从此处获取： http://www.kynosarges.de/DotNetVersion.html ）

首先，它检查是否存在指示已安装的.NET Framework版本的注册表项。如果注册表项不存在，它将提示用户下载.NET Framework。如果用户说是，它将打开下载URL。 （您可能必须将脚本中指定的版本更改为4.0版。）

First, it checks for the presence of a registry entry that indicates the version of the .NET framework that is installed. If the registry entry is not present, it prompts the user to download the .NET framework. If the user says Yes, it opens the download URL. (You may have to change the version it specifies in the script to version 4.0.)

我也遇到过有关CodeProject的这篇文章，这可能是一种更全面，更可定制的方式来寻找所需的内容，尽管可能需要更多工作才能理解，并且必须进行修改才能使用4.0版。

I also came across this article on CodeProject, which may be a more comprehensive and customizable way of doing what you're looking for, although it may take more work to understand and will have to be modified to work with version 4.0.