I'm working with the latest version of 7.5.7

I have a Poco Decorated class ...

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace uPost.Data
{
    using Umbraco.Core.Persistence.DatabaseAnnotations;
    using Umbraco.Core.Persistence;

    [TableName(uPost.Constants.CustomDBObjects.WeddingVendors)]
    [PrimaryKey("Id")]
    public class WeddingVendor
    {
        public WeddingVendor()
        {
            Id = Guid.NewGuid();
        }

        [PrimaryKeyColumn(AutoIncrement =false, Clustered =true)]
        public Guid Id { get; set; }

        public string Name { get; set; }

        public string Url { get; set; }

    }
}

I'm trying to just insert a new record in my api...

namespace uPost.Controllers
{
    using System.Collections.Generic;
    using System.Web.Http;
    using Umbraco.Web.WebApi;
    using System.Threading.Tasks;

    using Data;

    public class WeddingVendorApiController : UmbracoApiController
    {

        [HttpGet]
        public IEnumerable<WeddingVendor> GetAll()
        {
            var db = ApplicationContext.DatabaseContext.Database;

            return db.Fetch<WeddingVendor>("Select * from " + uPost.Constants.CustomDBObjects.WeddingVendors);
        }

        [HttpGet]
        public void Insert(string Name, string Url)
        {
            var newVendor = new WeddingVendor() { Name = Name, Url = Url };

            var db = ApplicationContext.DatabaseContext.Database;
            db.Insert(newVendor);
        }


    }
}

The table is created just fine using ...

    var logger = LoggerResolver.Current.Logger;
    var dbContext = ApplicationContext.Current.DatabaseContext;
    var dbhelper = new DatabaseSchemaHelper(dbContext.Database, logger, dbContext.SqlSyntax);

    dbhelper.CreateTable<Data.WeddingVendor>(false);

When i try to insert i get the following error...

Cannot insert the value NULL into column 'Id', table 'DB54305ngp17.dbo.uPost_WeddingVendors'; column does not allow nulls. INSERT fails. The statement has been terminated.

When i debug my object has is completely filled out... Id has a guid value. is there something special i'm missing? this is my first time doing this in Umbraco... my background in EF i feel i'm doing everything right. please help.