Последовательность содержит более одного элемента при наличии .Include ⇐ C#

[Гость]

In my application I have an entity called Board. This board has a list of the Column entity. When I am trying to get a specific Board and include the Columns with EF Core, I am geting the "Sequence contains more than one element." Error.

Get Board function:

public async Task GetBoardByWorkspaceIdAndBoardIdAsync(WorkspaceId workspaceId, BoardId boardId) { var result = await dbContext .Boards .Where(board => board.WorkspaceId == workspaceId && board.Id == boardId) .Include(board => board.Columns) .FirstOrDefaultAsync(); return result; } Board class

public BoardId Id { get; } public string Name { get; private set; } public WorkspaceId WorkspaceId { get; } public ICollection Columns { get; protected set; } = new List(); Board configuration

public void Configure(EntityTypeBuilder builder) { builder.ToTable("Boards"); builder.HasKey(board => board.Id); builder.Property(board => board.Id) .HasConversion( boardId => boardId.Value, value => BoardId.Create(value)); builder.Property(board => board.Name) .HasMaxLength(50) .IsRequired(); builder.Property(board => board.WorkspaceId) .HasConversion( workspaceId => workspaceId.Value, value => WorkspaceId.Create(value)) .IsRequired(); builder.HasMany(board => board.Columns) .WithOne() .HasForeignKey(column => column.BoardId) .OnDelete(DeleteBehavior.Cascade); } Column class

public ColumnId Id { get; } public string Name { get; } public BoardId BoardId { get; } Column configuration

public void Configure(EntityTypeBuilder builder) { builder.ToTable("Columns"); builder.HasKey(column => column.Id); builder.Property(column => column.Id) .HasConversion( columnId => columnId.Value, value => ColumnId.Create(value)); builder.Property(column => column.Name) .HasMaxLength(50) .IsRequired(); } the migration and updating the database goes fine, but when fetching the Board I get the error. When I remove the include, everything works fine.

Anybody has an idea of what I am doing wrong here?


Источник: https://stackoverflow.com/questions/780 ... -a-include