Exception thrown: 'System.Collections.Generic.KeyNotFoundException' in MongoDB.EntityFrameworkCore.dll (MongoDB)

Question

I have .NET 8 project using MongoDB.EntityFrameworkCore v7.0.0-preview and MongoDB.Driver v2.24.0.

I created my MyDbContext class inherited from the DbContext and in the void OnModelCreating(ModelBuilder modelBuilder) method performed all required attributes mapping.

But when I called var drawings = db.Drawings.ToList(); I got the following exception:

Exception thrown: System.Collections.Generic.KeyNotFoundException in MongoDB.EntityFrameworkCore.dll

An unhandled exception of type 'System.Collections.Generic.KeyNotFoundException' occurred in MongoDB.EntityFrameworkCore.dll The given key was not present in the dictionary.

I checked all attributes binding. For example, binding the property Name looks like below:

b.Property(c => c.Name).HasElementName("name");

How can I understand what causes the exception? I tried to analyze the callback stack. But it doesn’t help a much and the InnerException is null.

I have a few collections and they are loaded without a problem. But this one thought the exception and I can’t understand why.

Thanks