Entity Framework Core: Type Udt is not supported on this platform. (Spatial Data - Geography)

Question

I\'m experimenting with entity framework core and stumbled upon an error I\'ve never seen before and can\'t figure out how to fix it. I\'m using .net Core Web API 2.0 with E

Answer 1

Ok here is how I solved it:

The purpose is to keep geography in Entity Framework Core (without using DbGeography)

1) I created a struct called Location:

public struct Location
{
    public double Longitude { get; set; }
    public double Latitude { get; set; }
}

2) Add it to your EF Entity Model

public class User
{
    public Location Location { get; set; }
}

3) Hide it in your modelbuilder

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity().Ignore(x => x.Location);
}

4) Generate a Migration (Add-Migration migrationname)

5) Go to your migration file 1231randomnumbers1231_migrationname.cs and add the following (this way we create another column of type geography named Location) and then update your database (update-database):

migrationBuilder.Sql(@"ALTER TABLE [dbo].[User] ADD [Location] geography NULL");

6) (optional) I created a static class to update the db, handy if you have a Location column in mulple tables.

public static class GeneralDB
{

    public static async Task UpdateLocation(DbContext ctx, string table, Location location, int id)
    {
        Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en-US");

        string query = String.Format(@"UPDATE [dbo].[{0}] SET Location = geography::STPointFromText('POINT(' + CAST({1} AS VARCHAR(20)) + ' ' + CAST({2} AS VARCHAR(20)) + ')', 4326) WHERE(ID = {3})"
        , table.ToLower(), location.Longitude, location.Latitude, id);
        await ctx.Database.ExecuteSqlCommandAsync(query);
    }
    public static async Task GetLocation(DbContext ctx, string table, int id)
    {
        Location location = new Location();

        using (var command = ctx.Database.GetDbConnection().CreateCommand())
        {
            string query = String.Format("SELECT Location.Lat AS Latitude, Location.Long AS Longitude FROM [dbo].[{0}] WHERE Id = {1}"
                , table, id);
            command.CommandText = query;
            ctx.Database.OpenConnection();
            using (var result = command.ExecuteReader())
            {
                if (result.HasRows)
                {
                    while (await result.ReadAsync())
                    {
                        location.Latitude = result.GetDouble(0);
                        location.Longitude = result.GetDouble(1);
                    }
                }

            }
        }

        return location;
    }
}

This only works in EF Core 2.0

Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en-US");

For EF Core 1.0 you would have to find an alternative way to replace a ',' with '.'. A good old fashion .Replace() method could do the job.

location.Longitude.ToString().Replace(',', '.')

7) CRUD Examples:

7.1: Read

public async Task GetByIdAsync(int id)
{
    User user =  await ctx.User.AsNoTracking().SingleOrDefaultAsync(x => x.Id == id);

    user.Location = await GeneralDB.GetLocation(ctx, "user", id);
    return user;
}

7.2: Create

public async Task CreateAsync(User entity)
{

    ctx.User.Add(entity);
    await ctx.SaveChangesAsync();
    await GeneralDB.UpdateLocation(ctx, "user", entity.Location, entity.Id);
    return entity;  
}

7.3: Update

public async Task UpdateAsync(User entity)
{
    ctx.User.Attach(entity);
    ctx.Entry(entity).State = EntityState.Modified;
    await ctx.SaveChangesAsync();

    await GeneralDB.UpdateLocation(ctx, "user", entity.Location, entity.Id);

    return entity;
}