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• Create a many to many relationship in Entity Framework skipping extra data in the link table.

  - by Paul Smith

  I would like to model the following many to many relationship. Table A ID Field1 Field2 Table B ID Field1 Field2 LinkTable A_ID B_ID Field_I_want_to_ignore As I understand it, if LinkTable.Field_I_want_to_ignore was not present, the Entity Model Designer would automatically create a Many to Many relationship between entity A and entity B. However, because this field exists in the database the designer won't do it for me. I can delete the Field_I_want_to_ignore from the LinkTable Entity that the designer created for me, but how do I eliminate the LinkTable entity altogether and create the many to many relationship I want? I'm not averse to digging through the XML, just at the moment I can't see how to achieve what I want.

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• Getting a set of elements using linq

  - by MarceloRamires

  I have the following piece of XML: <xml> <ObsCont xCampo="field1"> <xTexto>example1</xTexto> </ObsCont> <ObsCont xCampo="field2"> <xTexto>example2</xTexto> </ObsCont> <ObsCont xCampo="field3"> <xTexto>example3</xTexto> </ObsCont> </xml> How do I (using linq) get for example what is inside the xTexto tag that has as parent the ObsCont with the xCampo attribute "field2" ? (c#, vb.net, your choice)

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• Return nested alias for linq expression

  - by Schotime

  I have the following Linq Expression var tooDeep = shoppers .Where(x => x.Cart.CartSuppliers.First().Name == "Supplier1") .ToList(); I need to turn the name part into the following string. x.Cart.CartSuppliers.Name As part of this I turned the Expression into a string and then split on the . and removed the First() argument. However, when I get to CartSuppliers this returns a Suppliers[] array. Is there a way to get the single type from this. eg. I need to get a Supplier back. Thanks

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• LINQ and set difference

  - by Pierre

  I have two collections a and b. I would like to compute the set of items in either a or b, but not in both (a logical exclusive or). With LINQ, I can come up with this: IEnumerable<T> Delta<T>(IEnumerable<T> a, IEnumerable<T> b) { return a.Except (b).Union (b.Except (a)); } I wonder if there are other more efficient or more compact ways of producing the difference between the two collections.

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• Linq to SQL ordered child collection

  - by Matt Connolly

  Is there a way to define a default order column from a child collection? In my case, I have a Form entity that has a collection of FormItem entities called FormItems. FormItem has a property called DisplayOrder (int). I want to make sure that any Form entities I return from a method have that collection properly ordered. Is there a way to do this before returning the result? For example, I tried this but the list is not actually sorted: var form = context.Forms.FirstOrDefault(x => x.IsDeleted == false && x.FormName == formName); if (form != null) { form.FormItems.OrderBy(x => x.DisplayOrder); // I can't even figure out a way to cast this next line so that it will compile // form.FormItems = form.FormItems.OrderBy(x => x.DisplayOrder); } return form; Is there a way to do this without using DataLoadOptions?

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• How to SET ARITHABORT ON for connections in Linq To SQL

  - by Laurence

  By default, the SQL connection option ARITHABORT is OFF for OLEDB connections, which I assume Linq To SQL is using. However I need it to be ON. The reason is that my DB contains some indexed views, and any insert/update/delete operations against tables that are part of an indexed view fail if the connection does not have ARITHABORT ON. Even selects against the indexed view itself fail if the WITH(NOEXPAND) hint is used (which you have to use in SQL Standard Edition to get the performance benefit of the indexed view). Is there somewhere in the data context I can specify I want this option ON? Or somewhere in code I can do it?? I have managed a clumsy workaround, but I don't like it .... I have to create a stored procedure for every select/insert/update/delete operation, and in this proc first run SET ARITHABORT ON, then exec another proc which contains the actual select/insert/update/delete. In other words the first proc is just a wrapper for the second. It doesn't work to just put SET ARITHABORT ON above the select/insert/update/delete code.

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• Insert xelements using LINQ Select?

  - by Simon Woods

  I have a source piece of xml into which I want to insert multiple elements which are created dependant upon certain values found in the original xml At present I have a sub which does this for me: <Extension()> Public Sub AddElements(ByVal xml As XElement, ByVal elementList As IEnumerable(Of XElement)) For Each e In elementList xml.Add(e) Next End Sub And this is getting invoked in a routine as follows: Dim myElement = New XElement("NewElements") myElement.AddElements( xml.Descendants("TheElements"). Where(Function(e) e.Attribute("FilterElement") IsNot Nothing). Select(Function(e) New XElement("NewElement", New XAttribute("Text", e.Attribute("FilterElement").Value)))) Is it possible to re-write this using Linq syntax so I don't need to call out to the Sub AddElements but could do it all in-line Many Thx Simon

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• Using LINQ to search a byte array for all subarrays that start/stop with certain byte

  - by Joel B

  I'm dealing with a COM port application and we have a defined variable-length packet structure that I'm talking to a micro-controller with. The packet has delimiters for the start and stop bytes. The trouble is that sometimes the read buffer can contain extraneous characters. It seems like I'll always get the whole packet, just some extra chatter before/after the actual data. So I have a buffer that I append data to whenever new data is received from the COM port. What is the best way to search this buffer for any possible occurrences of my packet? For example: Say my packet delimiter is 0xFF and I have an array as such { 0x00, 0xFF, 0x02, 0xDA, 0xFF, 0x55, 0xFF, 0x04 } How can I create a function/LINQ-statment that returns all subarrays that start and end with the delimiter (almost like a sliding-correlator with wildcards)? The sample would return the following 3 arrays: {0xFF, 0x02, 0xDA, 0xFF}, {0xFF, 0x55, 0xFF}, and {0xFF, 0x02, 0xDA, 0xFF, 0x55, 0xFF}

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• Weird mapping error in linq-to-sql dbml file in VS2010

  - by rwwilden

  Since I switched to VS2010, several times a day I get a compilation error in my dbml file: DBML1005: Mapping between DbType 'bigint' and Type 'MyNamespace.SecurityToken' in Column 'SecurityToken' of Type 'Employee' is not supported When I restart VS2010 the error disappears. I have no problems running my application using this dbml file (specifically, there are no problems getting correct values inside the SecurityToken property of Employee objects). The SecurityToken property is of an enum type defined as follows: [Flags] public enum SecurityToken : long { None = 1, Admin = 2, ...... } The SecurityToken column in the database is of type bigint. Am I missing something? It's especially weird that the error only happens sometimes, when I'm writing code that isn't related at all to the LINQ model.

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• Use LINQ and lambdas to put string in proper case

  - by Tobias Funke

  I have this function called ProperCase that takes a string, then converts the first letter in each word to uppercase. So ProperCase("john smith") will return "John Smith". Here is the code: public string ProperCase(string input) { var retVal = string.Empty; var words = input.Split(' '); foreach (var word in words) { if (word.Length == 1) { retVal += word.ToUpper(); } else if (word.Length > 1) { retVal += word.Substring(0, 1).ToUpper() + word.Substring(1).ToLower(); } retVal += ' '; } if (retVal.Length > 0) { retVal = retVal.Substring(0, retVal.Length - 1); } return retVal; } This code workds perfectly, but I'm pretty sure I can do it more elegantly with LINQ and lambdas. Can some please show me how?

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• Build dynamic LINQ?

  - by d daly

  Hi Im using #LINQ# to query data, but can anyone tell me how to build the query dynamically, if the user only wants to report on say 1 of the 3 fields? (see below) Thanks DD var query = from cl in db.tblClaims join cs in db.tblCases on cl.ref_no equals cs.ref_no where cl.claim_status == "Appeal" && cl.appeal_date >= Convert.ToDateTime(txtReferedFromDate.Text) && cl.appeal_date <= Convert.ToDateTime(txtReferedToDate.Text) && cs.referred_from_lho == dlLHO.Text && cs.adviser == dlAdviser.Text select new { Ref = cs.ref_no, ClaimType = cl.claim_type, ClaimStatus = cl.claim_status, AppealDate = cl.appeal_date }; gvReport.DataSource = query;

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• LINQ: Dot Notation vs Query Expression

  - by Martín Marconcini

  I am beginning to use LINQ in general (so far toXML and toSQL). I've seen that sometimes there are two or more ways to achieve the same results. Take this simple example, as far as I understand both return exactly the same thing: SomeDataContext dc = new SomeDataContext(); var queue = from q in dc.SomeTable where q.SomeDate <= DateTime.Now && q.Locked != true orderby (q.Priority, q.TimeCreated) select q; var queue2 = dc.SomeTable .Where( q => q.SomeDate <= DateTime.Now && q.Locked != true ) .OrderBy(q => q.Priority) .ThenBy(q => q.TimeCreated); Besides any mistake I may have made in the syntax or a missing parameter or difference, the idea is that there are two ways to express the same thing; I understand that the first method has some limitations and that the "dot notation" is more complete, but besides that, are there any other advantages?

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• Problem with linq-to-xml

  - by phenevo

  I want by linq save my xml in csv and I have o problem. This bracket are here beacuse without it this code is not displaying (why ? ) bracket results bracket <Countries country="Albania"><Regions region="Centralna Albania"><Provinces province="Durres i okolice"><Cities city="Durres" cityCode="2B66E0ACFAEF78734E3AF1194BFA6F8DEC4C5760"><IndividualFlagsWithForObjects Status="1" /><IndividualFlagsWithForObjects Status="0" /><IndividualFlagsWithForObjects magazyn="2" /></Cities></Provinces></Regions></Countries><Countries .... XDocument loaded = XDocument.Load(@"c:\citiesxml.xml"); // create a writer and open the file TextWriter tw = new StreamWriter("c:\\XmltoCSV.txt"); // Query the data and write out a subset of contacts var contacts = (from c in loaded.Descendants("Countries") select new { Country = (string)c.Element("Country"), Region = (string)c.Element("region"), Province= (string)c.Element("province"), City = (string)c.Element("city"), Hotel = (string)c.Element("hotel") }).ToList(); Problem is that loaded.Descendants("Countries") gives me 45 countries but all fields are null.

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• How to delete data in DB efficiently using LinQ to NHibernate (one-shot-delete)

  - by kastanf

  Hello, producing software for customers, mostly using MS SQL but some Oracle, a decision was made to plunge into Nhibernate (and C#). The task is to delete efficiently e.g. 10 000 rows from 100 000 and still stay sticked to ORM. I've tried named queries - link already, IQuery sql = s.GetNamedQuery("native-delete-car").SetString(0, "Kirsten"); sql.ExecuteUpdate(); but the best I have ever found seems to be: using (ITransaction tx = _session.BeginTransaction()) { try { string cmd = "delete from Customer where Id < GetSomeId()"; var count = _session.CreateSQLQuery(cmd).ExecuteUpdate(); ... Since it may not get into dB to get all complete rows before deleting them. My questions are: If there is a better way for this kind of delete. If there is a possibility to get the Where condition for Delete like this: Having a select statement (using LinQ to NHibernate) = which will generate appropriate SQL for DB = we get that Where condition and use it for Delete. Thanks :-)

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• Equality Comparison with Multiple Instances/IEqualityComparer problems in LINQ

  - by Stacey

  This is similar to my last question; but from a different angle. http://stackoverflow.com/questions/2792393/see-if-item-exists-once-in-enumerable-linq Given the following set of items, and lists containing them... Item 1 Item 2 Item 3 Item 4 Item 5 class Item { string Name { get; set; } } List<Item> available = new List<Item>() { Item 1 Item 1 Item 2 Item 3 Item 5 } List<Item> selected = new List<Item>() { Item 1 Item 2 Item 3 } I need to make a third List that has everything from "available", except what is in "selected". However 'Item 1' is in 'available' twice, but only in 'selected' once. Since they are instances of the same item, I am having trouble figuring out the appropriate logic to accomodate this. The final array should look like... List<Item> selectable = new List<Item>() { Item 1 Item5 }

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• LINQ OrderBy with more than one field

  - by brainimus

  I have a list that I need sorted by two fields. I've tried using OrderBy in LINQ but that only allows me to specify one field. I'm looking for the list to be sorted by the first field and then if there are any duplicates in the first field to sort by the second field. For example I want the results to look like this (sorted by last name then first name). Adams, John Smith, James Smith, Peter Thompson, Fred I've seen that you can use the SQL like syntax to accomplish this but I am looking for a way to do it with the OrderBy method. IList<Person> listOfPeople = /*The list is filled somehow.*/ IEnumerable<Person> sortedListOfPeople = listOfPeople.OrderBy(aPerson => aPerson.LastName, aPerson.FirstName); //This doesn't work.

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• Populate DataTable with LINQ in C#

  - by RaYell

  I have a method in my app that populates DataTable with the data using the following code: DataTable dt = this.attachmentsDataSet.Tables["Attachments"]; foreach (Outlook.Attachment attachment in this.mailItem.Attachments) { DataRow dr = dt.NewRow(); dr["Index"] = attachment.Index; dr["DisplayName"] = String.Format( CultureInfo.InvariantCulture, "{0} ({1})", attachment.FileName, FormatSize(attachment.Size)); dr["Name"] = attachment.FileName; dr["Size"] = attachment.Size; dt.Rows.Add(dr); } I was wondering if I could achieve the same functionality using LINQ in order to shorten this code a bit. Any ideas?

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• Linq To Sql: Compiled Queries and Extension Methods

  - by Beni

  Hi community, I'm interessted, how does Linq2Sql handles a compiled query, that returns IQueryable. If I call an extension method based on a compiled query like "GetEntitiesCompiled().Count()" or "GetEntitiesCompiled().Take(x)". What does Linq2Sql do in the background? This would be very bad, so in this situation I should write a compiled query like "CountEntitiesCompiled". Does he load the result (in this case "GetEntitiesCompiled()") into the memory (mapped to the entity class like "ToList()")? So what situations make sense, when the compiled queries return IQueryable, that query is not able to modify, before request to the Sql-Server. So in my opinion I can just as good return List. Thanks for answers!

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• Get the first and second objects from a list using LINQ

  - by Vahid

  I have a list of Person objects. How can I get the first and second Person objects that meet a certain criteria from List<Person> People using LINQ? Let's say here is the list I've got. How can I get the first and second persons that are over 18 that is James and Jodie. public class Person { public string Name; public int age; } var People = new List<Person> { new Person {Name = "Jack", Age = 15}, new Person {Name = "James" , Age = 19}, new Person {Name = "John" , Age = 14}, new Person {Name = "Jodie" , Age = 21}, new Person {Name = "Jessie" , Age = 19} }

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• Group by/count in LINQ against SQL Compact 3.5 SP2

  - by bash74

  Hello, I am using LINQ-To-Entities in C# and run queries against a SQL Compact Server 3.5 SP2. What I try to achieve is a simple group by with an additional where clause which includes a Count(). var baseIdent="expression"; var found=from o in ObservedElements where o.ObservedRoots.BaseIdent==baseIdent group o by o.ID into grouped where grouped.Count()==1 select new {key=grouped.Key, val=grouped}; foreach(var res in found){ //do something here } This query throws the famous exception "A parameter is not allowed in this location. Ensure that the '@' sign and all other parameters are in a valid location in the SQL statement." When I either omit the where clause OR directly enter the expression "expression" in the query (where o.ObservedRoots.BaseIdent=="expression") everything just works fine. Does anybody know how to solve this? Workaround would also be fine? Thanks in advance, Sebastian

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• help with linq query

  - by Luis

  Hi, i am trying to get some data, but i dont know how can i do a if in linq, this is how i am trying to do from so in db.Operations where ((opType!= "0" ? so.Operation == int.Parse(opType) : false) && (idState!=0 ? so.State == idState : false) && (start != null ? so.StartDate == start : false) && (end !=null ? so.EndDate == end : false)) select so the optype is a Int, the idState is a Int, end is a datetime, start is a datime what i am trying to do is, if those aren't null they add to the query function, so i can get all data together

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• joining two sets in LINQ

  - by user343209

  var setsA = new List<SetA> { new SetA { SsnA = "3450734507", name = "setA"}, new SetA { SsnA = "6833467788", name = "setA"}, new SetA { SsnA = "5452347787", name = "setA"}, new SetA { SsnA = "9345345345", name = "setA"}, }; var setsB = new List<SetB> { new SetB { SsnB = "5452347787" ,name = "setB"}, new SetB { SsnB = "9345345345", name = "setB"}, }; when i use this linq: var Set = from seta in setsA join setb in setsB on seta.SsnA equals setb.SsnB select new { SSN = seta.SsnA, NAME = setb.name }; i get this value: { SSN = "5452347787", NAME = "setB" } { SSN = "9345345345", NAME = "setB" } but i would want to have SET which combines these two and the result would be: { SSN = "3450734507", NAME = "setA" } { SSN = "6833467788", NAME = "setA" } { SSN = "5452347787", NAME = "setB" } { SSN = "9345345345", NAME = "setB" } This would be a result set that would tell me with the name NAME property which set it was taken from, if SSN was found in SetA and SetB it would have property NAME = "setB" could someone help me with this?

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• Linq query with subquery as comma-separated values

  - by Keith

  In my application, a company can have many employees and each employee may have have multiple email addresses. The database schema relates the tables like this: Company - CompanyEmployeeXref - Employee - EmployeeAddressXref - Email I am using Entity Framework and I want to create a LINQ query that returns the name of the company and a comma-separated list of it's employee's email addresses. Here is the query I am attempting: from c in Company join ex in CompanyEmployeeXref on c.Id equals ex.CompanyId join e in Employee on ex.EmployeeId equals e.Id join ax in EmployeeAddressXref on e.Id equals ax.EmployeeId join a in Address on ax.AddressId equals a.Id select new { c.Name, a.Email.Aggregate(x=x + ",") } Desired Output: "Company1", "[email protected],[email protected],[email protected]" "Company2", "[email protected],[email protected],[email protected]" ... I know this code is wrong, I think I'm missing a group by, but it illustrates the point. I'm not sure of the syntax. Is this even possible? Thanks for any help.

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• Linq to SQL gives NotSupportedException when using local variables

  - by zwanz0r

  It appears to me that it matters whether you use a variable to temporary store an IQueryable or not. See the simplified example below: This works: List<string> jobNames = new List<string> { "ICT" }; var ictPeops = from p in dataContext.Persons where ( from j in dataContext.Jobs where jobNames.Contains(j.Name) select j.ID).Contains(p.JobID) select p; But when I use a variable to temporary store the subquery I get an exception: List<string> jobNames = new List<string> { "ICT" }; var jobs = from j in dataContext.Jobs where jobNames.Contains(j.Name) select j.ID; var ictPeops = from p in dataContext.Persons where jobs.Contains(p.JobID) select p; "System.NotSupportedException: Queries with local collections are not supported" I don't see what the problem is. Isn't this logic that is supposed to work in LINQ?

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• Multiple Table Join in Linq C# Dynamically

  - by kmkperumal

  I have 3 data table a,b,c In this I need to write Join Query Dynamically using linQ. The Selecting columns given by customer and Condition columns also given customer at run time. So i need to create Querys dynamically.Please check below example.Because i dont which table they want and which column also For example Select a.c1,a.c2,b.c1,b.c2 From a Left Join b on a.c1=b.c1 2.Select c.c1,c.c2,a.c1,a.c2 From c Left Join a on c.c3=a.c1 3.Select a.c1,a.c2,b.c1,b.c2,c.c1,c.c2 From a Left Join b on a.c2=b.c2 Left join c on c.c1=a.c1 Like i need create different set of query's. Please help me on this.

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