Programmatically create content database in C# (SP 2013)

The goal is to have a web user interface with the option to create new site collections with new Content Database.

With the admin user I can manually in the CA create new Content Databases. I can also create a new site collection in this content database.

The idea was to create an event receiver (C#). If the user adds data to a table, the mentioned actions are to be executed.

Experiments: a) Console application - works!

using (SPSite site = new SPSite("http://sp2013")) {
  using (SPWeb spWeb = site.OpenWeb()) {
      SPWebApplication elevatedWebApp = spWeb.Site.WebApplication;
        elevatedWebApp.ContentDatabases.Add("sp2013", "WSS_Content_80_" + DateTime.Now.ToString("yyyymmddhhMMss"), null, null, 10, 15, 0);
    }
}

b) Event Receiver - Only create site collections works, creation of content databases does not work! Error: Access Denied.

c) Web Service - Does not work! Error: Access Denied.

So, why do I get the error Access Denied when I can create site collections, but only content databases creation not go?

Finally I executed PS Script - but this also doesn´t work.

# AUTHOR: Paul Kotlyar
# CONTACT: unclepaul84@gmail.com
# DESCRIPTION: sets an option on content web service that allows updating of SP Administration objects such as SPJobDefinition from content web applications
function Set-RemoteAdministratorAccessDenied-False()
{
    # load sharepoint api libs
    [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint") > $null
    [System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint.Administration") > $null

  # get content web service
 $contentService = [Microsoft.SharePoint.Administration.SPWebService]::ContentService
  # turn off remote administration security
 $contentService.RemoteAdministratorAccessDenied = $false
  # update the web service
 $contentService.Update()
}

Maybe somebody knows a solution?