To show a label on the Inno wizard page displaying the amount of require disk space. Add the following code section to the installer script.

[Code]
procedure InitializeWizard;
begin
WizardForm.DiskSpaceLabel.Visible := True; // False to hide
end;

Download installer script FreeDiskSpace.iss

To check that DotNet framework is installed during an Inno install. Add the following code section to the install script.

; Check if dot net is insalled
[code]
function FrameworkIsNotInstalled: Boolean;
begin
Result := not RegKeyExists(HKEY_LOCAL_MACHINE, 'Software\Microsoft\.NETFramework\policy\v4.0');
end;

// Install dot net with feedback
[Code]
procedure InstallFramework;
var
StatusText: string;
ResultCode: Integer;
begin
StatusText := WizardForm.StatusLabel.Caption;
WizardForm.StatusLabel.Caption := 'Installing .NET framework...';
WizardForm.ProgressGauge.Style := npbstMarquee;
try
if not Exec(ExpandConstant('{tmp}\dotNetFx40_Full_x86_x64.exe'), '/q /noreboot', '', SW_SHOW, ewWaitUntilTerminated, ResultCode) then
begin
// you can interact with the user that the installation failed
MsgBox('.NET installation failed with code: ' + IntToStr(ResultCode) + '.',
mbError, MB_OK);
end;
finally
WizardForm.StatusLabel.Caption := StatusText;
WizardForm.ProgressGauge.Style := npbstNormal;
end;
end;

In the files section add the dotnet installer file. Note the flags AfterInstall and Check that will call the functions to check if DotNet is installed and instal if required.

Source: "C:\Example\dotNetFx40_Full_x86_x64.exe"; DestDir: {tmp}; Flags: deleteafterinstall; AfterInstall: InstallFramework; Check: FrameworkIsNotInstalled

Download the installer script CheckDotNet.iss

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CLIQUE CONCOMBRE DES MERS

To check if a program exists before installing with Inno add the following code section to the installer script. In this example we will be testing for the file “c:\Example\Test.exe”. If the test.exe file exist a message box showing “Program Already Exists” will be displayed and the installer will terminate.

[Code]
function IsMyProgramInstalled: boolean;
begin
result := FileExists('C:\Example\Test.exe');
end;

function InitializeSetup: boolean;
begin
result := not IsMyProgramInstalled;
if not result then
MsgBox('Program Already Exists', mbError, MB_OK);
end;


Download the installer script IsMyProgramInstalled.iss

When installing a program using Inno, to create an empty directory you will need to add a dirs section to the installer script.

[Dirs]
Name: "{app}\Example1"

Download installer script CreateEmptyDirectories.iss