在mongodb上按对象的子集合项属性查询

Question

I am storing a collection of the following:

{
    "_id" : ObjectId("59ffdb0c70a6560df428aaa3"),
    "name" : "Contact Information",
    "description" : "Basic contact information about myself",
    "questions" : [ 
        {
            "caption" : "First Name",
            "value" : ""
        }, 
        {
            "caption" : "Last Name",
            "value" : ""
        }, 
        {
            "caption" : "Email",
            "value" : ""
        }, 
        {
            "caption" : "Date of bith (mm/dd/yyyy)",
            "value" : ""
        }, 
        {
            "caption" : "Street Address",
            "value" : ""
        }, 
        {
            "caption" : "Address Line 2",
            "value" : ""
        }, 
        {
            "caption" : "State",
            "value" : ""
        }, 
        {
            "caption" : null,
            "value" : null
        }, 
        {
            "caption" : "Postal Code",
            "value" : ""
        }, 
        {
            "caption" : "Country",
            "value" : ""
        }
    ]

I need to query based on the parent property "name" or by questions collection and property "caption"

So I have constructed the following query:

var result =(from Query in this.CoreService.QuestionCategoriesCollection().AsQueryable()
                            from Questions in Query.questions
                            where Questions.caption.ToLower().Contains(filter.ToLower())
                            select Query).ToList();

However, when the query runs I receive the following exception:

Exception has occurred: CLR/System.NotSupportedException An exception of type 'System.NotSupportedException' occurred in MongoDB.Driver.dll but was not handled in user code: '$project or $group does not support {document}.' at MongoDB.Driver.Linq.Translators.AggregateLanguageTranslator.TranslateValue(Expression node) at MongoDB.Driver.Linq.Translators.AggregateLanguageTranslator.TranslateMapping(ProjectionMapping mapping) at MongoDB.Driver.Linq.Translators.QueryableTranslator.TranslateProjectValue(Expression selector) at MongoDB.Driver.Linq.Translators.QueryableTranslator.TranslateSelectMany(SelectManyExpression node) at MongoDB.Driver.Linq.Translators.QueryableTranslator.TranslateWhere(WhereExpression node) at MongoDB.Driver.Linq.Translators.QueryableTranslator.TranslateSelect(SelectExpression node) at MongoDB.Driver.Linq.Translators.QueryableTranslator.TranslatePipeline(PipelineExpression node) at MongoDB.Driver.Linq.Translators.QueryableTranslator.Translate(Expression node, IBsonSerializerRegistry serializerRegistry, ExpressionTranslationOptions translationOptions) at MongoDB.Driver.Linq.MongoQueryProviderImpl 1.GetExecutionModel(Expression expression) at MongoDB.Driver.Linq.MongoQueryableImpl 2.ToCurs or(CancellationToken cancellationToken) at MongoDB.Driver.IAsyncCursorSourceExtensions.ToList[TDocument](IAsyncCursorSource`1 source, CancellationToken cancellationToken) at projectname.Services.Questions.GetQuestions(String filter) in c:\\developerment\\project\\project\\Service\\Questions.cs:line 24 at projectnameAPI.Controllers.QuestionsController.Get(String filter) in c:\\developerment\\project\\project\\Controllers\\QuestionsController.cs:line 31 at Microsoft.Extensions.Internal.ObjectMethodExecutor.Execute(Object target, Object[] parameters) at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.d__12.MoveNext()

I don't know what other way to write the query using linq.

Answer 1

I ended up rewriting my query to this.

    var result =this.CoreService.QuestionCategoriesCollection().Find(c=>c.name.ToLower().Contains(filter.ToLower())
    || c.questions.Any(q=>q.caption.ToLower().Contains(filter.ToLower())));

Answer 2

A cleaner - but more raw - way. Given the following collection schema example:

public class Parent
{
    public IEnumerable<Child> Children { get; set; }
}

public class Child
{
    public string Id { get; set; }
}

Get the parent by child id:

var dictionary = new Dictionary<string, object>
{
    "Children.Id" : "childId"
}
var data = this.ParentCollection().Find(new MongoDB.Driver.CommandDocument(dictionary));