When I run a Select and want the result to be of a specific type, like this:
persons.Query().Where(p => p.Uid == personUid).Select(p => new MyDto
{
PersonUid = p.Uid
});I get this error
System.InvalidOperationException: When called from 'VisitMemberInit', rewriting a node of type 'System.Linq.Expressions.NewExpression' must return a non-null value of the same type. Alternatively, override 'VisitMemberInit' and change it to not visit children of this type.
at System.Linq.Expressions.ExpressionVisitor.VisitAndConvert[T](T node, String callerName)
at System.Linq.Expressions.ExpressionVisitor.VisitMemberInit(MemberInitExpression node)
at BccCode.Linq.Client.Evaluator.SubtreeEvaluator.Visit(Expression exp)
at System.Linq.Expressions.ExpressionVisitor.VisitLambda[T](Expression`1 node)
at BccCode.Linq.Client.Evaluator.SubtreeEvaluator.Visit(Expression exp)
at System.Linq.Expressions.ExpressionVisitor.VisitUnary(UnaryExpression node)
at BccCode.Linq.Client.Evaluator.SubtreeEvaluator.Visit(Expression exp)
at System.Dynamic.Utils.ExpressionVisitorUtils.VisitArguments(ExpressionVisitor visitor, IArgumentProvider nodes)
at System.Linq.Expressions.ExpressionVisitor.VisitMethodCall(MethodCallExpression node)
at BccCode.Linq.Client.Evaluator.SubtreeEvaluator.Visit(Expression exp)
at BccCode.Linq.Client.Evaluator.SubtreeEvaluator.Eval(Expression exp)
at BccCode.Linq.Client.Evaluator.PartialEval(Expression expression, Func`2 fnCanBeEvaluated)
at BccCode.Linq.Client.ApiQueryProvider.TranslateExpression(Expression expression, QueryableTypeMode expectedTypeMode)
at BccCode.Linq.Client.ApiQueryProvider.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
at BccCode.Linq.Client.QueryableAsyncExtensions.AsAsyncEnumerable[TSource](IQueryable`1 queryable, CancellationToken cancellationToken)
at BccCode.Linq.Client.QueryableAsyncExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
This bug encourages inefficient use of the library because the easiest path would be to materialize the response and then project it to MyDto, but that means I would request from the API all properties of the Person object when I only need a subset.
A workaround for keeping this efficient until this gets fixed would be to project this to an anonymous object, then materialize the query then project it to MyDto.
persons.Query().Where(p => p.Uid == personUid).Select(p => new
{
PersonUid = p.Uid
}).ToListAsync(cancellationToken)
.ContinueWith((task) => {
return task.Result.Select(p => new MyDto
{
PersonUid = p.PersonUid
}).ToList();
}, cancellationToken);
When I run a Select and want the result to be of a specific type, like this:
I get this error
This bug encourages inefficient use of the library because the easiest path would be to materialize the response and then project it to MyDto, but that means I would request from the API all properties of the Person object when I only need a subset.
A workaround for keeping this efficient until this gets fixed would be to project this to an anonymous object, then materialize the query then project it to MyDto.