$scriptPath = $MyInvocation.MyCommand.Path
write-host $scriptPath
$nofilePath = Split-Path -Parent $scriptPath

function Export-Excel([Array]$data, [string]$outfilename) {
  function Get-Keys([Array]$data) {
    $keys = New-Object System.Collections.Generic.HashSet[string]
    $data | ForEach-Object {
      $item = $_
      $item | Get-Member -MemberType NoteProperty | select -ExpandProperty Name | ForEach-Object {
        $keys.Add($_) | Out-Null
      }
    }
    return $keys
  }

  $keys = Get-Keys($data)
  try {
    $excel = New-Object -ComObject Excel.Application
    $excel.Visible = $true
    $excel.DisplayAlerts = $true
    $book = $excel.Workbooks.Add()
    $book.Sheets(1).Name = "data"
    $sheet = $book.Sheets("data") # 扱いやすいようにシートを取得します
    $sheet.Name                   # hoge と出るはずです
    $keys | ForEach-Object { $j = 1 } {
      $sheet.Cells.Item(1, $j) = $_
      $j++
    }
    $data | ForEach-Object { $i = 2 } {
      $item = $_
      $keys | ForEach-Object { $j = 1 } {
        $key = $_
        $sheet.Cells.Item($i, $j) = $item.$key
        $j++
      }
      $i++
    }

    $book.SaveAs($nofilePath + "\" + $outfilename)
    $excel.Quit()  # Excel の終了
  }
  finally {
    [System.Runtime.Interopservices.Marshal]::ReleaseComObject($excel) | Out-Null # 変数の破棄
    [System.Runtime.Interopservices.Marshal]::ReleaseComObject($sheet) | Out-Null # 変数の破棄
    # null破棄
    $excel, $book, $sheet | foreach {$_ = $null}
  }
}


$data = @()
$data += [PSCustomObject]@{
  Name  = "unko"
  Name2 = "unkounko"
  Name3 = "unkounkounko"
}
$data += [PSCustomObject]@{
  Name  = "unko2"
  Name2 = "unkounko2"
}

Export-Excel $data "a.xlsx"