Id Not auto incrementing as expected

I am using the latest version of LiteDb on a .Net project. A user can fill in a form and create a person. The class for this is;

public class Witness
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public string First_Name { get; set; }
        public string Surname { get; set; }
        public string DOB { get; set; }
        public int Age { get; set; }
        public string Address { get; set; }
        public string Postcode { get; set; }
        public DateTime Update { get; set; }
        public string URN { get; set; }
        public string Email { get; set; }
        public string HomePhone { get; set; }
        public string WorkPhone { get; set; }
        public string MobilePhone { get; set; }
        public string Occupation { get; set; }
        public string PlaceOfBirth { get; set; }
        public string[] Investigations { get; set; }
        public bool IsActive { get; set; }
    }

The winform calls a method to create the person as follows;

public static int CreateWitness(string Title, string FirstName, string SurName,string DOB,string Address,string Postcode, string Email,
            string Mobile, string Home, string Work, string Occupation, string POB, int Age,string[] Investigations)
        {
           
            //try
            //{
                using (var db = new LiteDatabase(WitnessDb))
                {                  
                    var witnesses = db.GetCollection<Classes.Witness>("Witness");
                    var witness = new Classes.Witness
                    {
                        Title = Title,
                        First_Name = FirstName,
                        Surname = SurName,
                        DOB = DOB,
                        Address = Address,
                        Postcode = Postcode,
                        Email = Email,
                        MobilePhone = Mobile,
                        WorkPhone = Work,
                        HomePhone = Home,
                        Occupation = Occupation,
                        Update = DateTime.UtcNow,
                         URN = SurName + DateTime.UtcNow.ToString("ddMMHHmmssfffffff"),
                        // Investigations = new string[]{""}
                        PlaceOfBirth = POB,
                        Age = Age,
                        Investigations = Investigations
                        
                    };

                    witnesses.Insert(witness);
                    return witness.Id;
                   }

This initially worked fine I think (wasn’t thoroughly tested). However, the user can add and delete people and now it throws an exception for a duplicate Id.

So if I create 3 people (Id’s 1,2 & 3) and then delete person 2 (Id 2) and then try to create a new person - it throws an exception for a duplicate Id (duplicate being 3). I would expect it to create Id 4 and so on.

I have deleted my Db and tried again but no joy. I have tried indexing and shrinking the Db also.

Where am i going wrong?

[Brown3246]

Confirmed the fix appears to work. I employ Shrink when the app opens so that would explain why the problem occurs after an application restart. Many thanks for the quick fix - and for LiteDb!

[mbdavid]

You can download from master branch and compile (if you have vs2017) - otherwise, I will publish in this holiday a new version on nuget/github release