How do i check if a particular MSI is installed?

Question

I'm writing a powershell script that will install some dependencies for my webapp. In my script, I'm running into a recurring problem of checking if a particular application is installed. it seems there's a unique way of checking if an application exists for each application (ie: by checking the existing of this folder or this file on c:). Is there not a way that i can check if an application is installed by querying a list of installed applications?

Answer 1

Here is the code I use sometimes (not too often, so...). See the help comments for details.

<#
.SYNOPSIS
    Gets uninstall records from the registry.

.DESCRIPTION
    This function returns information similar to the "Add or remove programs"
    Windows tool. The function normally works much faster and gets some more
    information.

    Another way to get installed products is: Get-WmiObject Win32_Product. But
    this command is usually slow and it returns only products installed by
    Windows Installer.

    x64 notes. 32 bit process: this function does not get installed 64 bit
    products. 64 bit process: this function gets both 32 and 64 bit products.
#>

function Get-Uninstall
{
    # paths: x86 and x64 registry keys are different
    if ([IntPtr]::Size -eq 4) {
        $path = 'HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall\*'
    }
    else {
        $path = @(
            'HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall\*'
            'HKLM:\Software\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*'
        )
    }

    # get all data
    Get-ItemProperty $path |
    # use only with name and unistall information
    .{process{ if ($_.DisplayName -and $_.UninstallString) { $_ } }} |
    # select more or less common subset of properties
    Select-Object DisplayName, Publisher, InstallDate, DisplayVersion, HelpLink, UninstallString |
    # and finally sort by name
    Sort-Object DisplayName
}

Get-Uninstall

Answer 2

To get a list of installed applications try:

$r = Get-WmiObject Win32_Product | Where {$_.Name -match 'Microsoft Web Deploy' }
if ($r -ne $null) { ... }

See the docs on Win32_Product for more info.