User260076833 posted
Hello,
I want to execute a PowerShell script, which is contained in a TextBox. The output of the script should be written into another TextBox. Te execution should be started, when the user clicks on a button "Execute".
The script should be executed asynchroneously: When a long script produces output from time to time, the new portions of output should be written to the output TextBoox as they are produced.
My approach is like this: When the button "Execute" is clicked, the button handler method creates a PowerShell instance and registers a callback method "output_DataAdded", which is called whenever new portions of output arrive. This method then sends the
output to the client using SignalR (IHubContext.Clients.All.write).
There is a problem which I cannot solve:
- When the user first clicks on "Execute", the script is invoked and the callback method is called, which in turn calls a client-side method.
The output is written into the output TextBox. Everything is ok so far. - When the user then clicks on "Execute" again, nothing happens. I can verify by setting a breakpoint that the callback method "output_DataAdded" is called.
Even the call to "IHubContext.Clients.All.write" is reached, but it never makes it to the client. I can verify this by adding an alert trace at the client side method.
This alert is only executed, when the user clicks the button for the first time. The procedure is not repeatable for some reason.
In order to further analyze what's going on here, I removed all the PowerShell related code. The event handler method for the button click then only calls HubContext.Clients.All.write. This version works perfectly: Whenever
the user clicks the button, an output text is written into the output TextBox.
So the procedure is repeatable.
I conclude that the problem must result from the way I process the PowerShell script. There must be something that prevents the procedure from being repeatable. Maybe I need to clean up something after the invokation is done? I don't know.
Below is a minimal version of my code.
I hope that someone can see what's the problem here.
(Note that I started different threads on similar topics, because I don't want to mix problems with SignalR and problems with PowerShell code.)
Thanks
Magnus
OutputHub.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Microsoft.AspNet.SignalR;
namespace Playground.lab.PowerShellExecution.Asynchroneous
{
public class OutputHub : Hub
{
public void write(String txt)
{
Clients.All.write(txt);
}
}
}
Test.aspx:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Test.aspx.cs" Inherits="Playground.lab.PowerShellExecution.Asynchroneous.Test" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<script src="../../../Scripts/jquery-3.2.1.min.js"></script>
<script src="../../../Scripts/jquery.signalR-2.2.2.min.js"></script>
<script src="../../../signalr/hubs"></script>
<script type="text/javascript">
function write( txt)
{
alert(txt);
$('#' + '<% = txt_Output.ClientID%>').append(txt + "<br />");
}
$(function ()
{
var outputHub = $.connection.outputHub;
outputHub.client.write = write;
$.connection.hub.start();
});
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="txt_Input" runat="server" Height="250" Width="400" TextMode="MultiLine" Text="get-date"></asp:TextBox>
<br />
<asp:Button ID="btn_Execute" runat="server" Text="Execute" OnClick="btn_Execute_Click"/>
<br />
<asp:TextBox ID="txt_Output" runat="server" Height="250" Width="400" TextMode="MultiLine"></asp:TextBox>
</div>
</form>
</body>
</html>
Test.aspx.cs:
using System;
using System.Management.Automation;
using System.Management.Automation.Runspaces;
using System.Security;
using System.Collections.ObjectModel;
using Microsoft.AspNet.SignalR;
namespace Playground.lab.PowerShellExecution.Asynchroneous
{
public partial class Test : System.Web.UI.Page
{
private Runspace runSpace;
protected void Page_Load(object sender, EventArgs e)
{
if (Session["output"] == null)
Session["output"] = "";
txt_Output.Text = (String) Session["output"];
}
protected void btn_Execute_Click(object sender, EventArgs e)
{
//execute_1(); // works only for the first click
execute_2(); // works always, without Powershell
}
private void execute_1()
{
Session["output"] = "";
PowerShell psh = PowerShell.Create();
PSDataCollection<PSObject> output = new PSDataCollection<PSObject>();
output.DataAdded += output_DataAdded;
psh.AddScript(txt_Input.Text);
psh.Streams.Error.DataAdded += Error_DataAdded;
var result = psh.BeginInvoke<PSObject, PSObject>(null, output);
}
private void execute_2()
{
IHubContext c = GlobalHost.ConnectionManager.GetHubContext<OutputHub>();
write("CLICK");
}
void output_DataAdded(object snd, DataAddedEventArgs evt)
{
PSDataCollection<PSObject> col = (PSDataCollection<PSObject>)snd;
Collection<PSObject> rsl = col.ReadAll();
foreach (PSObject r in rsl)
{
write(r.ToString());
}
}
void Error_DataAdded(object sender, DataAddedEventArgs e)
{
//display error message in UI
}
private void write(String txt)
{
IHubContext c = GlobalHost.ConnectionManager.GetHubContext<OutputHub>();
String t;
if (Session["output"] != null)
t = (String)Session["output"];
else
t = "";
t = t + txt + "\n";
Session["output"] = t;
c.Clients.All.write( t);
}
}
}
How to execute a Powershell script asynchronously with SignalR?
