I am trying to create a linq statement to filter otu results using an any clause. My issue is that I dont have a single value to compare against.
In the example below I have a PropertyTaxBill entity that is the parent. Each one has a collection of TaxPropertyAssessmentDetails attached to it.
In this query people can specify that they only want to deal with bills pertaining to a specific class strata so I check to see if any values exist in the classStrata variable. If so then the user selected specific ones. I was trying to do an any clause on the classStrata but instead of giving it a single value to match on I was trying to select all the values in the TaxPropertyAssessmentDetails collection attached to the PropertyTaxBill. Is this possible?
using (var dataContext = contextProvider.GetContext())
{
var query = dataContext.PropertyTaxBills.Where(x => x.Id > 1);
var classStrata = new int[0];
if (classStrata != null && classStrata.Any())
{
query = query.Where(x => classStrata.Any(y => y == x.TaxPropertyAssessmentDetails.SelectMany(z => z.PropertyTaxClassStrataId)));
}
}
You need to use contains so that ef is able to translate to a ef query.
Not sure that i understood your model correctly. Here's a example with a model. Please tell me if i understood incorrect so i can fix it.
public void TestMethod1()
{
IEnumerable<TaxBill> TaxBills = new List<TaxBill>();
var query = TaxBills.Where(x => x.Id > 1);
var classStrata = new int[0];
if (classStrata != null && classStrata.Any())
{
query = query.Where(x => x.AssessmentDetails.Any(ad => ad.TaxClassStrataId.Any(cs => classStrata.Contains(cs))));
}
}
And the entities
public class TaxBill
{
public int Id { get; set; }
public ICollection<AsessmentDetails> AssessmentDetails { get; set; }
}
public class AsessmentDetails
{
public ICollection<int> TaxClassStrataId { get; set; }
}
Related
Hope you're doing well,
I was trying to optimize my reads with entity framework, where I arrived at a position, where I get a record from database by id, and I want to include a one-to-many related list, but I don't want to get all data of the list, just a few, so I want to kind of paginate it.
I want to do this process as long as data is in IQueryable state, I don't want to load all data of list in memory and that paginate it as enumerable.
Let's say the query is like below:
var author = await _dbContext.Authors.Where(x => x.Id == id)
.Include(x => x.Books) // <-- paginate this !!??
.FirstOrDefaultAsync();
Entities represent Data state. Pagination and presentation concerns are View state. Entity Framework can help bridge that gap, but it does so by enabling projection so that you can build View state from Data state. Don't pass entities to views, instead build and pass ViewModels to represent the data in accordance to translations and limitations you want for the view.
For instance if you want to pass Author details with their 5 most recent books:
public class AuthorViewModel
{
public int Id { get; set; }
public string Name { get; set; }
// Any other relevant fields...
public ICollection<BookViewModel> RecentBooks = new List<BookViewModel>();
}
public class BookViewModel
{
public int Id { get; set; }
public string Name { get; set; }
public DateTime PublishedDate { get; set; }
// Any other relevant fields...
}
var author = await _dbContext.Authors
.Where(x => x.Id == id)
.Select( x => new AuthorViewModel
{
Id = x.Id,
Name = x.Name,
RecentBooks = x.Books
.OrderByDescending(b => b.PublishedDate)
.Select(b => new BookViewModel
{
Id = b.Id,
Name = b.Name,
PublishedDate = b.PublishedDate
}).Take(5)
.ToList()
}).SingleOrDefault();
This gives you the benefit of structuring the data how you want to present it, while generating efficient queries against the database. You can configure tools like Automapper to perform this kind of mapping to use it's ProjectTo<AuthorViewModel>() as a more succinct alternative.
My Web API Controller has a method that retrieves a specified number of decriptions from a database table. There are duplicate descriptions with different IDs, so sometimes the query returns duplicates when I use SELECT TOP. I also added random (ORDER BY NEWID) to lessen the chances of getting dups but duplicates still get returned sometimes. I want to change the query to SELECT DISTINCT but not sure how to do that in my particular case. Using First() seems to be complicated here. Can anyone help? My method is below:
public List<String> GetRandomDescriptions(string cat, string subcat, int n)
{
using (MyContext ctx = new MyContext())
{
var temp = ctx.Interactions.Where(d => (d.Category.Equals(cat) && d.Subcategory.Equals(subcat)))).OrderBy(d=>Guid.NewGuid()).Take(n).Select(d=>d.Description).ToList();
return temp;
}
}
Here is my class:
[Table("[Records]")]
public class Interaction
{
[Key, Column("RECORD_ID")]
public string DescId { get; set;}
public string Category { get; set; }
public string Subcategory { get; set; }
public string Description{get; set;}
}
You can use something like this
var result = ctx.Interactions
.Where(d => d.Category == cat && d.Subcategory == subcat)
.Select(d => d.Description)
.Distinct()
.Take(n)
.ToList();
The key points are - first apply the filter, then select the description, then make it distinct and finally take the required number of items.
If you really need to pick a random items, then just insert your OrderBy before Take.
You don't need to do the funny OrderBy construct. Try something like this:
public List<String> GetRandomDescriptions(string cat, string subcat, int n)
{
using (MyContext ctx = new MyContext())
{
var temp = ctx.Interactions
.Where(d => d.Category.Equals(cat) && d.Subcategory.Equals(subcat)))
.Select(d=>d.Description)
.Distinct()
.ToList();
return temp;
}
}
I have the following model:
public class Clip {
public Guid ClipId { get; set; }
public IList<StateChange> StateChanges { get; set; }
}
public class StateChange {
public string OldState { get; set; }
public string NewState { get; set; }
public DateTime ChangedAt { get; set; }
}
And this is how a query raven:
var now = DateTime.UtcNow;
var since = now.AddSeconds(60);
string state = "some state of interest";
using (var session = docStore.OpenSession()) {
RavenQueryStatistics stats;
session.Query<Clip>()
.Statistics(out stats)
.Where(
p => p.StateChanges.Any(a => (since > a.ChangedAt && a.NewState == state))
&& !p.StateChanges.Any(a => (a.OldState == state && now > a.ChangedAt)))
.ToArray();
return stats.TotalResults;
}
I want to get the count for all Clip records that have a (StateChange.CreatedAt before since and NewState is "some state of interest") AND NOT have a (StateChange.CreatedAt before now and OldState is "some state of interest").
While the predicate used above works in linq to object, it doesn't seem to work in linq to raven (i.e. does not return the expected result). I suspect that this is because the expression && !.p.StateChanges.Any.... is never evaluated if the expression on the left-hand side evaluates to true. Is there a way to work around this?
It's not related to the evaluation of conditions. && works just fine.
The problem is that RavenDB doesn't properly handle queries that use .All(...) or !.Any(...). This is due to the way raven's dynamic index engine evaluates your linq statement. It wants to build a separate index entry for each of your StateChange entries, which won't work for operations that need to consider multiple related items, such as the different state changes.
There is an issue already logged for this here. It was closed in build 2151 to throw back a meaningful exception when you try to query in this way. Maybe at some future date they can reassess if there's some way to actually evaluate these types of queries properly instead.
Update
I've been thinking about your challenge, and another related one, and was able to come up with a new technique that will allow you to do this. It will require a static index and lucene query:
public class Clips_ByStateChange : AbstractIndexCreationTask<Clip>
{
public Clips_ByStateChange()
{
Map = clips =>
from clip in clips
select new {
OldState = clip.StateChanges
.Select(x => x.OldState + "|" + x.ChangedAt.ToString("o")),
NewState = clip.StateChanges
.Select(x => x.NewState + "|" + x.ChangedAt.ToString("o"))
};
}
}
var results = session.Advanced.LuceneQuery<Clip, Clips_ByStateChange>()
.Where(string.Format(
"NewState: {{{0}|* TO {0}|{1}}} AND -OldState: {{{0}|* TO {0}|{2}}}",
state, since.ToString("o"), now.ToString("o")));
Of course, you can still just take statistics on it if that's what you want.
How do I created the appropriate AbstractIndexCreationTask for the following scenario?
For a scenario of multiple blogs, how do I get the tags from specific blogs and the tag-count for these?
Members of interest for data-structure stored in RavenDB:
public class BlogPost {
public string BlogKey { get; set; }
public IEnumerable<string> Tags { get; set; }
/* ... */
}
The method I need to implement has the following signature:
public Dictionary<string, int> GetTagsByBlogs(string tag, params string[] blogKeys)
In normal LINQ I would write something like this:
var tags = from post in blogPosts
from tag in post.Tags
where blogKeys.Contains(post.BlogKey)
group tag by tag into g
select new {
Tag = g.Key,
Count = g.Count(),
};
But neither SelectMany or GroupBy are supported in RavenDB. I've tried different combinations for a map-reduce solution, but I can't figure out how to do this since the map and the reduce differ in data-structure.
How to create a tag cloud is described in the knowledge base of RavenDB.
In your case, you have to include the BlogKey in the index, especially in the group by clause:
public class Tags_Count : AbstractIndexCreationTask<BlogPost, Tags_Count.ReduceResult>
{
public class ReduceResult
{
public string BlogKey { get; set; }
public string Name { get; set; }
public int Count { get; set; }
}
public Tags_Count()
{
Map = posts => from post in posts
from tag in post.Tags
select new {
BlogKey = post.BlogKey,
Name = tag.ToString().ToLower(),
Count = 1
};
Reduce = results => from tagCount in results
group tagCount by new {
tagCount.BlogKey,
tagCount.Name } into g
select new {
BlogKey = g.Key.BlogKey,
Name = g.Key.Name,
Count = g.Sum(x => x.Count)
};
Sort(result => result.Count, SortOptions.Int);
}
}
Then query that index with the desired BlogKey:
var result = session.Query<Tags_Count.ReduceResult, Tags_Count>()
.Where(x => x.BlogKey = myBlogKey)
.OrderByDescending(x => x.Count)
.ToArray();
If you need to query for multiple blogs, you can try this query:
var tagsByBlogs = session.Query<Tags_Count.ReduceResult, Tags_Count>()
.Where(x => x.BlogKey.In<string>(blogKeys))
.OrderByDescending(x => x.Count)
.ToArray();
AFAIK that is as far as you can get with an index. You still have to aggregate the results on the client side as you did in your original question, except that you can skip the filtering on blogKeys:
var tags = from tag in tagsByBlogs
group tag by Name into g
select new {
Tag = g.Key,
Count = g.Count(),
};
Take a look at faceted search, you can specify the criteria at query time, like so:
var facetResults = s.Query<BlogPost>("BlogIndex")
.Where(x => x.BlogKey == "1" || x.BlogKey == "5" ...)
.ToFacets("facets/BlogFacets");
Then the grouping (and counts) is done on all the results that match the where clause.
Update You'll need an index that looks something like this:
from post in blogPosts
from tag in post.Tags
select new
{
post.BlogKey
Tag = tag
}
I have an TaxWork entity which is persisted using NHibernate. This entity has the following properties (among others):
public virtual TaxWorkType Type { get; set; } //Kctc.TaxWorkType is an enumeration
public virtual TaxWorkStatus Status { get; set; } //Kctc.TaxWorkStatus is an enumeration
public virtual LegalWorkPriority Priority { get; set; } //Kctc.LegalWorkType is an enumeration
public virtual User Handler { get; set; } //Kctc.BusinessLayer.Entities.User is another entity
public virtual int? CaseNumber { get; set; }
I am using Linq to NHibernate to pull of a subset of the tax work objects as follows (taxWorkRepository.All obviously returns an IQueryable):
foreach (TaxWork taxWork in taxWorkRepository.All.Where(x => x.CaseNumber == _caseNumber).OrderBy(x => x.DateCreated))
{
...
}
This works fine. I want to use projection in order to query only the columns that are required in this case. I am usnig the following code:
foreach (var taxWorkFragment in taxWorkRepository.All.Where(x => x.CaseNumber == _caseNumber).OrderBy(x => x.DateCreated).Select(x => new { Type = x.Type, DateCreated = x.DateCreated, Handler = x.Handler, Status = x.Status, Priority = x.Priority }))
{
...
}
However, I'm getting the following error when trying to create the anonymous type:
Invalid cast from 'Kctc.TaxWorkStatus' to 'Kctc.BusinessLayer.Entities.User'.
Where on earth is it getting the idea that it should be casting a TaxWorkStatus to a User?
Any suggestions whatsoever what might be going wrong?
Try to make like this:
foreach (var taxWorkFragment in taxWorkRepository.All.Where(x => x.CaseNumber == _caseNumber).OrderBy(x => x.DateCreated)
.Select(x => new TaxWork { Type = x.Type, DateCreated = x.DateCreated, Handler = x.Handler, Status = x.Status, Priority = x.Priority }))
{
...
}
It should help