Hey SO: From a performance perspective, is it better to wrap each statement that utilizes LINQ in a using() statement, or to declare a class-level instance and use in each method? For instance: public void UpdateSomeRecord(Record recordToUpdate) { using(var entities = new RecordDBEntities()) { // logic here... } } p...
Here is an example: Lets say I have 3 tables, Countries, People and Cities. City records have a non-nullable foreign key field identifying a country. People records have a nullable foreign key field identifying a country - they may be from an Eastern European country that no longer exists. I want to create a combined list of countries ...
This emits inner joins, which is what I want and works: var q = from itm in esdc.items join itmImg in esdc.itemImages on itm.itemId equals itmImg.itemId join itmIdent in esdc.itemIdentities on itm.imgIdentityId equals itmIdent.itemIdentityId join startImgs in esdc.vStartPgImgs on itmImg.imgId equals startImgs.imgId s...
I want to filter my results to take only the X amount of records. I am wondering how does Take() work? On this site I found: http://www.hookedonlinq.com/TakeOperator.ashx It says Take() "Throws an ArgumentNullException if source is null." So what should I do? I can't guarantee that everytime I do a Take() I will have some records in t...
I have a very simple linq to sql query in C#: int acctNum = 12345; var query = from p in db.table where p.ACCT_NO == acctNum select p; This generates the following SQL: exec sp_executesql N'SELECT [t0].field1, [t0].field2, [t0].ACCT_NO FROM [dbo].[table] AS [t0] WHERE [t0].[ACCT_NO] = @p0'...
Hi I am trying to figure out how to tackle this problem. I have to insert some data into 2 tables lets call them Table A and Table B. Table A has these columns AId<PK> A1 A2 A3 Table B has AId<PK> A1 B2 B3 B4 Now my first question was should another repository call another repository? I don't think this will solve my current proble...
I have the following connection string: "Data Source=localhost\\SQLEXPRESS;", it complains that '' is an invalid username. I can't quite remember the user name or password commands, nor can i remember if there's anything else i'm missing. Can someone help? ...
I have a property on a class that happens to be a Table. How do i add an item to this? ...
I was reading Steven Sanderson's book Pro ASP.NET MVC Framework and he suggests using a repository pattern: public interface IProductsRepository { IQueryable<Product> Products { get; } void SaveProduct(Product product); } He accesses the products repository directly from his Controllers, but since I will have both a web page a...
This is a strange LINQ-to-SQL problem which can't evaluate as an Enumerable (in SQL) but I can evaluate client side. I think it's related to my testing Binary property as 'null'. I need to determine when my Job is complete, which means that all Files in that Job have at least some data in their binary FileContents property. The proced...
Hi, In my program, there are two class, say, category and product, with each object of product hold a reference to the category it belongs to. When loading data from XML and store them in the database, a problem arise: If I create a category object and store it in the database first, there will be dirty data when creating product faile...
I have a table to store product reviews like this: Id -int ProductId -int Timestamp -datetime Comments -text Is there an easy way to count and determine the rate of reviews a product has received in any 60 minute timespan? ie. Widget1 maximum reviews/hour is 55. working with sql05. ...
Hi, I have a model on top of my database model and map the objects in my Repository. However, apparently it makes a difference whether I "select new" directly in my GetUsers or "select factoryresult" as implemented below. I get the error at runtime, that the method CreateFromDbModel does not have a translation to sql (System.NotSupport...
LINQ so far has been remarkably elegant, but to perform basic m2m queries it offers no solution I can imediately see. What's worse is that while it works for any other table relationship, LINQ is not giving me an association in the class structure for my m2m table. So I can do things like artwork.artists.where(...) //or artist.Artwo...
I am a beginner in LINQ. I am using .NET 3.5. and VS 2008. using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data.Linq.Mapping; using System.Data.Linq.Provider; namespace LINQ_to_SQL_Test { [Table(Name="Person")] public class Person { [Column(Name="ID", Storage="_ID...
Hi there, Been succcesfully adding records using Linq2Sql with the linq2sql genereated classes, works great.. But i need to now select the records, i can't seem to figure this out This is how i am adding records - reservation is a generated linq2sql class TestDataContext db = new TestDataContext(); db.Reserva...
What does it actually mean by the term "Entity" in LINQ? What is the difference between EntitySet and EntityRef when talking about LINQ? Can you give a real-world example? Like Order and OrderItems, etc? ...
I'm trying to do a query like so... query.Where(x => !string.IsNullOrEmpty(x.PropertyName)); but it fails... so for now I have implemented the following, which works... query.Where(x => (x.PropertyName ?? string.Empty) != string.Empty); is there a better (more native?) way that LINQ handles this? EDIT apologize! didn't include t...
I am trying to do record inserts on a table where the primary key is an Identity field. I have tried calling mycontext.ExecuteCommand("SET identity_insert myTable ON") but this doesn't do any good. I get an error saying that identity_insert is off when I submit changes. How can I turn it ON from the c# code before I submit changes? E...
I'm reading the book "ASP.NET 3.5 Social Networking - Andrew Siemer" and I got confused when he uses Repositories to access the data. Here is the idea of his code: public interface IAccountRepository { Account GetAcountByID(int acId); void SaveAccount(Account account); List<Account> GetAllAccounts(); } public class Account...