Running embedded PowerShell script from .Net program

 I have a web UI that allows writing Powershell scripts. Later this script is being sent to the backend and executed.

In this post, I will focus how to execute the Powershell inside c#. 

First of all you need to add to you project "System.Management.Automation" reference. If you are not sure where to take it from, just open windows PowerShell windows and type

[psobject].assembly.location

The output is the exact location of the DLL.

In my program, the purpose of the PowerShell is to give the user the ability to manipulate the data of some DataTable object. For this purpose the program will person 3 operations.

1. Create DataTable

2. Pass it to Powershell 

3. Change the DataTable from inside the PowerShell

4. Return the DataTable 

Create DataTable

           DataTable dt = new DataTable();
            dt.Columns.Add("ID",typeof(Int32));
            DataRow dr = dt.NewRow();
            dr["ID"] =22;
            dt.Rows.Add(dr);

Create a Powershell object and pass this DataTable to it

           InitialSessionState iss = InitialSessionState.CreateDefault();
            Runspace rs = RunspaceFactory.CreateRunspace(iss);
            rs.Open();
 
            string powershell = @"Param([system.Data.DataTable]$dt)   
                                  [system.Data.DataRow]$row = $dt.NewRow();
                                  $row.ID = 3;       
                                  $dt.Rows.Add($row); 
 
                                  return  ,[system.Data.DataTable]$dt; "; //here is the catch ","
 
 
            using (PowerShell powerShellInstance = PowerShell.Create())
            {
                powerShellInstance.Runspace = rs;
                powerShellInstance.AddScript(powershell);
                powerShellInstance.AddParameter("dt", dt);
 
                DataTable outDt = null;
 
                Collection<PSObject> PSOutput = powerShellInstance.Invoke();

Note the Powershell parameter. It expects to get the DataTable . After this the script adds a new record into the DataTable.

This problematic point that took me some time to figure is how to return the DataTable.

The "," sign before [system.Data.DataTable]$dt; is not a misstake.

If you don't put it the script will return System.Data.DataRow!!! object.

You actually need "," to specify that you are returning the collection of DataRows

What is left now is to read the content of the output. You can check if there are some errors

               //catch the errors
                foreach (var err in powerShellInstance.Streams.Error)
                {
                    var ex = err.Exception?.Message;
                }
and actually read the output DataTable

          //catch the output
                foreach (PSObject pSObject in PSOutput)
                {
                    outDt = (DataTable)pSObject.ImmediateBaseObject;
                }
 
            }


  

If we check the "outDt" is debugger, we will see row with a value "3" that we added in the 

Powershell script

Datatable created by Powershell manipulation


P.S. Point of concern. I am trying to figure out how I can secure the PowerShell 

script from harming my backend. I could not find a way in PowerShell to restrict my 

PowerShell access to my file system. To solve this problem, I wrapped the whole 

code in a custom restricted AppDomain.