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.

xvorsx · Accepted Answer · 2014-07-16 22:09:46Z

6

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);

answered Jul 16, 2014 at 22:09

xvorsx

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Comments

Keith Hill · Accepted Answer · 2013-10-28 04:52:46Z

3

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.

answered Oct 28, 2013 at 4:52

Keith Hill

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3 Comments

Sachin Sundar Over a year ago

But I would like to have "path" to be dynamic.

Keith Hill Over a year ago

powershell.AddScript(String.Format("Get-WinEvent '{0}' ...", path));

xvorsx Over a year ago

@KeithHill then you need to worry about script-injections, if path can come from the outside of author's code.

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