Cosmos DB update fails Unable to cast Guid to string - asp.net-core

Question

Tried to update a Cosmos DB record in ASP.NET core 3.1. But the update fails with the following message: "Unable to cast object of type 'System.Func'2[Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry,System.Guid]' to type 'System.Func'2[Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry,System.String]'
The error occurs on the saveCangesAsync();
Simplified, the code looks like:
// The service
public async Task<Todo> UpdateAsync(Todo entity)
{
var response = ctx.Todos.Update(entity);
await ctx.SaveChangesAsync(); // Error here
return response.Entity;
}
// The entity Todo
public class Todo
{
public Guid id { get; set; }
[Required(ErrorMessage = "Description is required")]
public string description { get; set; }
...
}
// The context
public class TodoDbContext : DbContext
{
public DbSet<Todo> Todos { get; set; }
public TodoDbContext(DbContextOptions<TodoDbContext> options) : base(options)
{
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.HasDefaultContainer("Todos");
}
}
// The controller
[HttpPut]
public async Task<IActionResult> Put(Todo todo)
{
try
{
if (ModelState.IsValid)
{
Todo td = await service.GetAsync(todo.id.ToString());
if (td != null)
{
td.description = todo.description;
var response = await service.UpdateAsync(td);
return Ok(response);
}
return BadRequest("Not found.");
}
else
{
return BadRequest(ModelState);
}
}
catch (Exception ex)
{
return BadRequest(ex.Message); // Exception here
}
}
I can insert, read, but not update, so following code runs fine (with a Guid as well)
public async Task<Todo> CreateAsync(Todo entity)
{
entity.id = Guid.NewGuid();
var response = await ctx.Todos.AddAsync(entity);
await ctx.SaveChangesAsync();
return response.Entity;
}
Thanks for any help!

Answer 1

Don't use "id", that will collide with the automatically generated id. Use another property or use "Id" (with a capital I) in stead, to solve the problem.

Answer 2

Is there any reason you're using Guid as your id type? In your Todo class you could write it like so:
public class Todo
{
[JsonProperty("id")
public string Id { get; set; }
[JsonProperty("description")
[Required(ErrorMessage = "Description is required")]
public string description { get; set; }
}
I'm assuming that you're using v3 of the Cosmos DB SDK. You would then just use Guid.NewGuid().ToString() to set the id as a Guid (but as a string type).