Start a process and manipulate stdin in PowerShell

gistfile1.ps1

try {
  $MyProcess = New-Object System.Diagnostics.Process
  
  $MyProcess.StartInfo.FileName = "c:\MyProcess.exe"
  $MyProcess.StartInfo.Arguments = "arguments for process"
  $MyProcess.StartInfo.UseShellExecute = $false
  $MyProcess.StartInfo.RedirectStandardInput = $true
  $MyProcess.Start()
  $StdIn = $MyProcess.StandardInput
  
  $StdIn.WriteLine("some data")
} finally {
  if($StdIn) {
    $StdIn.Close()
  }
}