Run powershell file from c#

RunPowershell.cs

using System.Management.Automation;
//....
public static async  Task<string> RunPowershellScript(string scriptName, Dictionary<string,string> parameters)
        {
            using (var ps = PowerShell.Create())
            {
                var script = string.Format(". \"{0}\" {1}", scriptName, string.Join(" ", parameters.Select(p => "-" + p.Key + " '" + p.Value + "'")));
                if (debug)
                {
                    log.Debug("Running the following script:\r\n " + script);
                }
                ps.AddScript(script);

                var task = Task<PSDataCollection<PSObject>>.Factory.FromAsync(ps.BeginInvoke(), ps.EndInvoke);
                var objs = await task;

                if (ps.Streams.Error.Count > 0)
                {
                    throw new Exception(ps.Streams.Error[0].ToString());
                }
                else
                {
                    if (objs.Count > 0)
                    {
                        var result = objs[0].ToString();
                        return string.IsNullOrEmpty(result) ? null : result;
                    }
                }
                return null;
            }
        }