Check if .NET 5.0 is installed in Inno Setup - .net-core

Question

I have the following .iss script to compile a games launcher I'm working on that uses .NET 5.0. Currently it tries to install .NET 5.0 from the installer it has every time instead of checking if its required first. I've found plenty of resources that tell you how to do it for the .NET Framework but hardly anything for .NET 5.0 which is a updated version of .NET Core. How do I check if .NET 5.0 is already installed before trying to install it anyway?
I also am aware that 5.0 is nearer end of life but I'm using Visual Studio 2019 which 6.0 isn't compatible with and would prefer not to have to use any work arounds to get 2019 to play ball with it.
#define AppName "LowPoly Games Launcher"
#define AppEXEName "LPG Launcher.exe"
[Setup]
AppName={#AppName}
[Files]
Source: "..\bin\Release\net5.0-windows\*"; DestDir: "{app}"; \
Flags: ignoreversion recursesubdirs;
Source: "Resources\windowsdesktop-runtime-5.0.17-win-x64.exe"; \
DestDir: "{app}"; Flags: ignoreversion deleteafterinstall
[Run]
Filename: "{app}\{#AppEXEName}"; \
Description: "{cm:LaunchProgram, {#StringChange(AppName, '&', '&&')}}"; \
Flags: nowait postinstall
Filename: "{app}\windowsdesktop-runtime-5.0.17-win-x64.exe"; \
Parameters: "/q/passive"; Flags: waituntilterminated; \
StatusMsg: Microsoft .NET Framework 5.0 is being installed. Please wait...

Answer 1

Based on:
How to get an output of an Exec'ed program in Inno Setup?
How to check that .NET is already installed
You can do:
[Code]
function IsDotNetInstalled(DotNetName: string): Boolean;
var
Cmd, Args: string;
FileName: string;
Output: AnsiString;
Command: string;
ResultCode: Integer;
begin
FileName := ExpandConstant('{tmp}\dotnet.txt');
Cmd := ExpandConstant('{cmd}');
Command := 'dotnet --list-runtimes';
Args := '/C ' + Command + ' > "' + FileName + '" 2>&1';
if Exec(Cmd, Args, '', SW_HIDE, ewWaitUntilTerminated, ResultCode) and
(ResultCode = 0) then
begin
if LoadStringFromFile(FileName, Output) then
begin
if Pos(DotNetName, Output) > 0 then
begin
Log('"' + DotNetName + '" found in output of "' + Command + '"');
Result := True;
end
else
begin
Log('"' + DotNetName + '" not found in output of "' + Command + '"');
Result := False;
end;
end
else
begin
Log('Failed to read output of "' + Command + '"');
end;
end
else
begin
Log('Failed to execute "' + Command + '"');
Result := False;
end;
DeleteFile(FileName);
end;
And it use it like:
if IsDotNetInstalled('Microsoft.NETCore.App 5.0.') then // ...