A PowerShell module for showing common dialogs. (Currently only supports open and save file dialogs.)

Dialogs.psd1

@{

    # MODULE
    Description        = "Common Dialogs Module"
    ModuleVersion      = '1.0'
    GUID               = '374EF8CD-AEC6-464C-92DA-290C662DA183'

    # AUTHOR
    Author             = 'Josh Einstein'

    # REQUIREMENTS
    PowerShellVersion  = '3.0'
    CLRVersion         = '4.0'
    RequiredModules    = @()
    RequiredAssemblies = @('PresentationFramework')

    # CONTENTS
    FormatsToProcess   = @()
    TypesToProcess     = @()
    ModuleToProcess    = 'Dialogs.psm1'
    NestedModules      = @()

}

Dialogs.psm1

#.SYNOPSIS
# Shows a file open or save dialog box and returns the selected file name.
function Select-File {

    [CmdletBinding(DefaultParameterSetName='Open')]
    param(

        # The initial file name
        [Parameter(Position=1)]
        [String]$FileName,

        # The caption of the dialog.
        [Parameter()]
        [String]$Title,

        # The initial directory that is displayed in the dialog.
        [Parameter()]
        [String]$InitialDirectory,

        # Prompts the user to create a new file or save to an existing file.
        [Parameter(ParameterSetName='Save')]
        [Switch]$Save,

        # Prompts the user to open an existing file or files.
        [Parameter(ParameterSetName='Open')]
        [Switch]$Open,

        [Parameter(ParameterSetName='Open')]
        [Switch]$AllowMultiple,

        # An array of file types to display in the drop down list in the
        # dialog. The syntax of the strings is as follows:
        # Description|mask[;mask;mask...]
        # The default is 'All Files (*.*)|*.*'
        [Parameter()]
        [String[]]$FileTypes = @(
            'All Files (*.*)|*.*'
        )

    )

    process {

        if ($PSCmdlet.ParameterSetName -eq 'Save') {
            $Dialog = New-Object Microsoft.Win32.SaveFileDialog
            $Dialog.OverwritePrompt = $true
        }
        else {
            $Dialog = New-Object Microsoft.Win32.OpenFileDialog
            $Dialog.CheckFileExists = $true
            if ($AllowMultiple) {
                $Dialog.Multiselect = $true
            }
        }

        if ($Title) { $Dialog.Title = $Title }
        else { $Dialog.Title = $PSCmdlet.ParameterSetName + " File" }

        # Convert any PowerShell paths to file system paths
        if ($FileName) { $FileName = $PSCmdlet.SessionState.Path.GetUnresolvedProviderPathFromPSPath($FileName) }
        if ($InitialDirectory) { $InitialDirectory = $PSCmdlet.SessionState.Path.GetUnresolvedProviderPathFromPSPath($InitialDirectory) } 

        # If they specified a filename but not initial direcotry,
        # use the path of the file as the initial directory.
        # Otherwise use the current $PWD working directory
        if (!$InitialDirectory) {
            if ($FileName) {
                $InitialDirectory = [System.IO.Path]::GetDirectoryName($FileName)
                $FileName = [System.IO.Path]::GetFileName($FileName)
            }
            else {
                $InitialDirectory = $PWD.ProviderPath
            }
        }

        $Dialog.FileName = $FileName
        $Dialog.InitialDirectory = $InitialDirectory
        $Dialog.Filter = $FileTypes -join '|'
        $Dialog.CheckPathExists = $true

        if ($Dialog.ShowDialog()) {
            if ($AllowMultiple) {
                Write-Output $Dialog.FileNames
            }
            else {
                Write-Output $Dialog.FileName
            }
        }

    }

}

Export-ModuleMember -Function *-*