Usage of powerShell.AddCommand

Question

I would like to execute this event using c#.

Get-WinEvent -Path 'D:\Events\myevents.evt' -Oldest | Select-Object -Property * | ForEach-Object {$_ | ConvertTo-Json}

I have written upto

 path = "D:\\Events\\myevents.evt";  
 var powerShell = PowerShell.Create();
 powerShell.AddCommand("Get-WinEvent");
 powerShell.AddParameter("Path");
 powerShell.AddArgument(path);
 powerShell.AddParameter("Oldest");
 powerShell.AddCommand("Select-Object");
 powerShell.AddParameter("Property");
 powerShell.AddArgument("*");

I am stuck on writing for ForEach-Object {$_ | ConvertTo-Json}. Let me know how to proceed.

Appreciate help.

Answer 1

Keith's answer is totally valid if Path come from trusted source. Otherwise, it can be vulnerable for script injection. (demo https://gist.github.com/vors/528faab6411db74869d4)

I suggest a compromised solution: wrap you script in a function, which takes dynamic arguments and Invoke it with AddScript(). Now you have a function in your powershell runspace/session. You can call this function with AddCommand() + AddParameter(). Remember, that you need to call powershell.Commands.Clear() after first Invoke, otherwise commands will be piped.

Code can look like that:

const string script = @"function wrapper($path) {return (Get-WinEvent -Path $path -Oldest | Select-Object -Property * | ForEach-Object {$_ | ConvertTo-Json}) }";
ps.AddScript(script);
ps.Invoke();
ps.Commands.Clear();
ps.AddCommand("wrapper").AddParameter("path", path);

Answer 2

You could just use the AddScript method:

powershell.AddScript("Get-WinEvent D:\Events\myevents.evt -Oldest | ConvertTo-Json");

I think you could also simplify that script and pipe directly to ConvertTo-Json.