C# How can I Kill a startet Process?

I developed a Webpage in ASP.NET - the page has a button that starts a DOS-Program on click.

Here is the Code:

if (!String.IsNullOrEmpty(endTime))
{
    Process p = new Process();
    p.StartInfo.WorkingDirectory = Server.MapPath("~/");
    p.StartInfo.FileName = Server.MapPath(apiFile);

    try
    {
        p.Start();
    }
    catch
    {
        throw new Exception(
            "Requested process (" + p.StartInfo.FileName 开发者_开发百科+ ") could not be started. Page: Api.aspx.cs, Method: UploadBtn_Click()");
    }

    System.Threading.Thread.Sleep(5000);

    Response.Redirect(Request.Url.ToString());
}

The code works fine and starts the Process.

Now the Problem:

I click on the button and the process starts (I see this in the database) and the program works fine, however, I want to stop the process now, but don't know how.

There isn't a DOS-Window where I can click "CTRL + C" or something.

What can I do to stop the process?

And which User is used for starting the Process?

---

Just use Process.Kill:

p.Kill();

UPDATE:
Because of your comment, I provide this as an alternative:
To kill a process without code, use the task manager (open it by using CTRL + SHIFT + ESC or CTRL + ALT + DEL -> Task manager), navigate to the "Processes" tab, choose "Show processes from all users", select your process and click "End process"...

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You can store Process object as field under the page class and call .Kill at with another button. But in this case you will be able to host only 1 process and should think of the way to make it safe to run only one.