Mono.dll caused an Access Violation using Npgsql

Using Npgsql and Unity 5.6.2f1 to connect with PostgreSQL and the following code:

public bool OpenDB()
    {
        string connectionString = "Host=**;Port=**;Database=**;Username=**;Password=**";


        // IDbConnection dbcon; ## CHANGE THIS TO
        try
        {
            //NpgsqlConnection dbcon;
            dbcon = new NpgsqlConnection(connectionString);
            dbcon.Open();
        }
        catch (Exception e)
        {
            Debug.Log("catch " + e);
            return false;
        }
        return true;

    }

Unity closes and the way I try to access the database in question seems to be wrong.

The plugins are installed and I have done all the necessary steps that explain from Npgsql. Attachment error.log to add more information if someone can help me.

Thanks in advance ] 1