I am usins LINQ TO ENTITY in order to filter a list of persons based on their phone number.
IEnumerable<Person> personsList = (from person in repoPersons.All()
where person.PhoneNumber.Contains(PhoneSearch)
select person).ToList();
repoPersons.All() contains all the persons read from the database.
PhoneSearch is the search term entered by the user.
The Phone number is saved in the database as a string in a special format: +1 (555) 555-6608 (as an example.
But I want to allow the user to search for 5555556608 without having to format it properly. (I want him to be able to search for part of the phone number too like 556608 and still get the result.
I tried to create a Method called RemoveSpecialCharactersInPhoneNumber that will remove the special characters and returns it and use it like this:
IEnumerable<Person> personsList = (from person in repoPersons.All()
where RemoveSpecialCharactersInPhoneNumber(person.PhoneNumber).Contains(PhoneSearch)
select person).ToList();
But I get this error:
LINQ to Entities does not recognize the method 'System.String RemoveSpecialCharactersInPhoneNumber(System.String)' method, and this method cannot be translated into a person expression.
So is there a way I can check if the PhoneNumber contains PhoneSearch without the special character, using LINQ TO ENTITY?
I know I can use LINQ TO ENTITY to get all the list and then use LINQ TO OBJECT to filter it but I am trying to avoid this approach.
Any solution or hint is greatly appreciated
The following isn't exactly neat and tidy, but it will solve your problem (as no method is trying to be incorrectly resolved on the SQL end)
IEnumerable<Person> personsList = (from person in repoPersons.All()
where person.Phone.Replace("+", "").Replace("(", "").Replace(")", "").Replace("-", "").Replace(" ", "").Contains(PhoneNumber)
select person).ToList()
It will give error because the linq to entity will be converted into SQL query so there is no method for RemoveSpecialCharactersInPhoneNumber in sql.
This is similar question.
Seems like as where clause is evaluated on server side, this method cannot be recognized.
CLR method needs to be converted to Cannonical mapping so that it can be executed on server.
Try doing
IEnumerable<Person> personsList = (from person in repoPersons.All().ToList()
where RemoveSpecialCharactersInPhoneNumber(person.PhoneNumber).Contains(PhoneSearch)
select person).ToList();
This will prevent LINQ from trying to resolve RemoveSpecialCharactersInPhoneNumber in the SQL layer, and instead it can be processed by your business layer as you described.
Related
At first you might think this is duplicate of this question but hopefully you will see it is not.
I also want to select groups of rows that are consecutive but consider that this time the entries are telephone numbers, therefore, stored as string.
I have been trying somethink like:
var numbers = await (from a in context.Telephones
from b in context.Telephones
Convert.ToInt32(a.Number) < Convert.ToInt32(b.Number) &&
Convert.ToInt32(b.Number) < (Convert.ToInt32(a.Number) + numberQuantity)
group b by new { a.Number }
into myGroup
where myGroup.Count() + 1 == numberQuantity
select myGroup.Key.Number).ToListAsync();
But this fails with:
LINQ to Entities does not recognize the method 'Int32 ToInt32(System.String)' method, and this method cannot be translated into a store expression.
I understand that LINQ to Entities does not support Convert.ToInt32 but I am running out of ideas here to make it work.
So if my database has:
2063717608
2063717609
2063717610
2063717611
2063717613
2063717614
How can I select consecutive rows based on the string values? And when querying for 3 consecutive numbers get results like:
From 2063717608 to 2063717610
From 2063717609 to 2063717611
1- If you are aware of performance side effect of calling AsEnumerable() cast your query and do conversion in memory on the retrieved entities.
2- If you don't want solution #1, you have to look for a way to solve the conversion problem:
2-1- Either change the column type in the database to int
2-2- Or select one of the solution previously proposed by other developers such as:
Problem with converting int to string in Linq to entities
I am trying to implement some search functionality within our app and have a situation where a User can select multiple Topics from a list and we want to return all activities that match at least one of the selected Topics. Each Activity can have 0-to-many Topics.
I can write a straight SQL query that gives me the results I want like so:
SELECT *
FROM dbo.ACTIVITY_VERSION av
WHERE ACTIVITY_VERSION_ID IN (
SELECT ACTIVITY_VERSION_ID
FROM dbo.ACTIVITY_TOPIC at
WHERE at.TOPIC_ID IN (3,4)
)
What I can't figure out is how to write a LINQ query (we are using Linq to Sql) that returns the same results.
I've tried:
activities.Where(x => criteria.TopicIds.Intersect(x.TopicIds).Any());
this works if activities is a list of in memory objects (i.e. a Linq to Objects query), but I get an error if I try to use the same code in a query that hits the database. The error I receive is:
Local sequence cannot be used in LINQ to SQL implementations of query operators except the Contains operator.
I believe that this means that Linq to Sql doesn't know how to translate either Intersect or Any (or possibly both). If that is the case, I understand why it isn't working, but I still don't know how to make it do what I want it to and my Google-fu has not provided me with anything that works.
Haven't tested it. But this is how you ll go about it.
List<int> IDs = new List<int>();
IDs.Add(3);
IDs.Add(4);
var ACTIVITY_VERSION_IDs = ACTIVITY_TOPIC
.Where(AT => IDs.Contains(AT.TOPIC_ID))
.Select(AT=>AT.ACTIVITY_VERSION_ID)
var results = ACTIVITY_VERSION
.Where(AV => ACTIVITY_VERSION_IDs.Contains(AV.ACTIVITY_VERSION_ID))
I recently found out that i cannot call any methods from within a linq query. I am trying to write a query that, on the where clause compares two byte arrays. The value on the database is a GUID of type Raw(32) and it is returned as a byte array. This is the record ID for this table. I need to compare it to another byte array. the second byte array could be converted to a string but since i cannot call methods from within linq i was unable to compare.
I tied a custom "Compare" method, i also wrote an extension method. All received an error indicating "LINQ to Entities does not recognize the method"
Here is the code for what i am trying to do. The where clause causes this error:
LINQ to Entities does not recognize the method 'Boolean SequenceEqual[Byte] (System.Collections.Generic.IEnumerable1[System.Byte], System.Collections.Generic.IEnumerable1[System.Byte])' method, and this method cannot be translated into a store expression."
EPSGEntities dbContex = new EPSGEntities();
byte[] byteArray = ParseHex(ViewState["itemID"].ToString());
var q = (from d in dbContex.EPSG_VSOREJECTS
where d.SDSRECID.SequenceEqual(byteArray)
select d).First();
What version of EntityFramework are you using? On EF6 I am able to simply do the following against a SQL 2012 table with a varbinary column:
var q = dbContext.EPSG_VSOREJECTS.FirstOrDefault(e => e.SDSRECID == byteArray);
Is the SDSRECID property on EPSGEntities of type byte[]?
The alternative here would be to go to straight Sql to get your object. Something like:
dbContext.Database.SqlQuery<EPSG_VSOREJECT>("SELECT TOP 1 *" +
"FROM dbo.EPSGEntities" +
"WHERE SDSRECID = #byteString",
new SqlParameter
{
ParameterName = "byteString",
Value = ViewState["itemID"].ToString(),
}).FirstOrDefault();
Linq to Entities in EF is awesome for most queries, but I sometimes drop into sql when I need to do something unsupported, complex, or just fast. Hope this helps!
I'm not entirely sure this works, but I've found calling .AsEnumerable() on the IQueryable object set lets me apply pretty much any code I wish:
var q = dbContex.EPSG_VSOREJECTS.
.AsEnumerable()
.Where(d => d.SDSRECID.SequenceEqual(byteArray));
Doing so seems to prevent EF from trying to translate the Where() clause into SQL syntax, but I have no real idea what the performance hit would/will be.
This is also using method syntax, since I'm not real familiar with query syntax. HTH.
EDIT:
As some others have noted, you have to be careful with how you add any of the iterative methods (AsEnumerable(), ToList(), etc.) since past that point you are no longer building SQL against your data store. Once you start iterating, EF will execute whatever query has been built up to that point, and from then on you are filtering the result set from the LINQ query.
In this case, I don't know that this can be avoided, unless someone can build the same query as a sproc (which EF can execute on your behalf).
I'm getting the error:
LINQ to Entities does not recognize the method 'Int32 LastIndexOf(System.String)'
method, and this method cannot be translated into a store expression.
When using this code to tell if a person's last name starts with certain characters:
persons = persons.Where(c => c.FullName.IndexOf(" ") > 0 &&
c.FullName.Substring(c.FullName.LastIndexOf(" ")+1).StartsWith(lastNameSearch));
Any clue how to achieve this without using LastIndexOf()? Maybe I have to check for this after I grab results from the database using ToList()?
You are limited by the set of canonical functions that can be translated into an SQL query, so any solution must be achieved with no more than the canonical functions offer.
Luckily, one of the supported functions is the bool Contains(string) instance method. You can rewrite your check as
persons = persons.Where(c => c.FullName.Contains(" " + lastNameSearch));
This is not exactly like your current version (because it will allow people with more than one name to match their second name, while the former won't), but it's pretty close and IMHO can be acceptable.
Of course it would be much better than any of this to keep the last names as a separate column in the database, if that is at all possible.
I dont't know how to describe the title better (so feel free to change) but essntial I want to produce the equivilent of the following statement in LINQ to SQL:
select * from products where category in ('shoes','boots')
The fields will be coming from the query string essentially (more secure than this but for ease of explanation) i.e
string[] myfields = request.querystring["categories"].split(',');
Thanks
Yes, you use Contains:
db.Products.Where(product => myFields.Contains(product.Category))
aka
from product in db.Products
where myFields.Contains(product.Category)
select product
As other have mentioned, yes it does using the .Contains method. To benefit the other random people that may arrive here via Bing (or any of the other search engines): Linq-To-Entities does not support the .Contains method in the current version. However, with a simple extension method, you can do so:
http://george.tsiokos.com/posts/2007/11/30/linq-where-x-in/
In theory you would use contains:
var productList = from product in context.Products
where myfields.contains(product.category)
select product
However you'll need to test this - I seem to recall there being a bug in the Linq2Sql optimizer when trying to deal with List<> and array values being used like this (it may have only occured if you tried to cast them as IQueryable)