protected async Task WriteJsonAsync(JsonTextWriter writer, ISelection selection, IExpressionTree fields)
{
var countField = fields.Children.FirstOrDefault(c => c.Node.Name == nameof(ISelection.Count) && typeof(ISelection).IsAssignableFrom(c.Node.ToLambdaExpression().Parameters[0].Type));
var normalFields = new ExpressionTree
{
Node = fields.Node,
Children = fields.Children.Where(c => c != countField).ToList()
};
await writer.WriteStartObjectAsync();
if (countField == null || normalFields.Children.Count != 0)
{
var items = selection.GetItems();
await WriteKvpAsync(writer, NamingStrategy.GetPropertyName("items", false), items, normalFields, null);
}
if (countField != null)
{
await SerializePropertyAsync(writer, selection, countField);
}
await writer.WriteEndObjectAsync();
}