This will allow the following PowerShell script to work. Powershell does not handle generic methods of classes lacking a a generic signature, or having a different generic signature than the method.

Add-Type -Path 'MongoDB.Bson.dll'
Add-Type -Path 'MongoDB.Driver.dll'
$cn = [MongoDB.Driver.MongoServer]::Create("mongodb://localhost/MyDb");
$db = $cn['EventLog'];
[MongoDB.Driver.MongoCollection[System.Diagnostics.EventLogEntry]]$events = $db['Events.Simple'];