Read and store to csv all users from active directory

//src :
//https://stackoverflow.com/questions/5162897/how-can-i-get-a-list-of-users-from-active-directory
//https://stackoverflow.com/questions/10606334/using-principalsearcher-to-find-users-with-or-parameters
//https://stackoverflow.com/questions/1785751/how-to-get-company-and-department-from-active-directory-given-a-userprincipa

//add ref to :
//System.DirectoryServices
//System.DirectoryServices.AccountManagement

string line="";

using (StreamWriter outfile = new StreamWriter(Application.StartupPath + "\\export" + DateTime.Now.ToString("yyyyMMddHHmmss").ToString() + ".csv", true))
{
	//streamwriter autoflush by default is true, on my test when reach the max memory, doing auto flush
	//outfile.AutoFlush = true;
	//otherwise you can use .Flush on every line

	using (var context = new PrincipalContext(ContextType.Domain, "x.com"))
	{
	   // query direct for a specific samaccount with : 
	   // using (var searcher = new PrincipalSearcher(new UserPrincipal(context) { SamAccountName = "pipiscrew" }))
	   // else get all :
	   using (var searcher = new PrincipalSearcher(new UserPrincipal(context)))
		{

			List<string> cols = new List<string> { "DisplayName", "samAccountName", "co",  "EmployeeNumber", "Company", "WhenCreated", "whenchanged", "sAMAccountType", "LogonCount", "PrimaryGroupID", "msRTCSIP-UserEnabled" };

			foreach (string col_item in cols)
			{
				line += "\"" + col_item + "\",";
			}

			outfile.WriteLine(line);

			foreach (var result in searcher.FindAll())
			{
				line = "";

				DirectoryEntry de = result.GetUnderlyingObject() as DirectoryEntry;

				foreach (string col_item in cols)
				{

					if (de.Properties[col_item].Value == null)
					{
						line += ",";
						continue;
					}

					line += "\"" + de.Properties[col_item].Value.ToString() + "\",";
				}
				outfile.WriteLine(line);

			}
		}
	}

}