linq

How do I access consecutive elements in an IQueryable<T> object?

I need to access the current and previous element in an IQueryable object. If I had an int array, I would do the following: var array = new int[]{0,1,2,3,4}; for(var i = 1; i<array.Length ; i++) { method1(array[i-1], array[i]); } I don't know to do the same with IQueryable, since it does not implement IList. ...

Vexing linq to sql predicate building in a for loop

I'm building a LINQ query using a loop that appends predicates using an array: foreach (string tag in tags) { result = result.Where(p => (p.TagsDelimited).Contains("," + tag + ",")); } This creates all the necessary clauses, but each clause compares only the last element in the tags array, producing the sql (((',' + [t0].[TagsDel...

DataContext. Is there a single method where I can add an extra WHERE?

So basically I have an application that works with just one user, but I'd like to make it multi-user. This would involve me logging a user in, and keeping the user ID in session, plus adding a user id column to my database tables. no biggy. I'd like to change my dbml, or use it's partial, so that any query I throw through it also gets ...

Problem with Linq inside a while-header

I'm trying to find the next available Groupname on my project. I want the groupnames look like "Gruppe 1", "Gruppe 2" and so on. So that's what i got so far: int i = 0; while ((from GroupViewModel g in _groups where g.GroupName == ("Gruppe " + (++i).ToString()) select g).Any()); Group group = new Group() { Name = string....

LINQ to SQL: union on constant values

I want to populate a dropdown with values from database and constant hard-coded literals using linq. For example, assuming I already have northwind datacontext, i want to populate the dropdown with category table and some constants so that the dropdown will have something like below. value text 0 [All] -1 [None] 1 Beverages 2 Condiment...

Remove Single Quotes From All Cells in a DataTable - Creating New Table - Using LINQ in Vb.Net

I have a table with many values inside of it that might have single quotes around them. I need to create a duplicate table without those single quotes. I can't modify the original table as I need to use it, 'as-is' later. I've done this with a table.Clone and using a foreach to loop through the rows and columns removing single quotes ...

Filtering a collection of items from contents of another collection.

This used to work for me and then it failed. I want to return only those items that contain all the filters, not at least one filter as it is doing now. WHat is wrong here? private IQueryable<IndexItem> FilteredIndex (IQueryable<IndexItem> index, IEnumerable<string> filters) { var filteredIndex= from f in filters.AsQueryab...

Sorting MultiValue data numerically OR alphabetically - LINQ to SQL and C#3.

I am having a problem giving a LINQ predicate the knowledge it needs to sort either alphabetically or numerically. I am working with a multi-value pivoted set of data with has a sortable column. The column is always stored as varchar in the DB, however, it has lookup knowledge of what that data type actually is. To simplify, in additio...

find non intersecting data set with linq

List<int> a = 1,2,3 List<int> b = 2,4,5 output 1,3,4,5 ...

how would i use linq to find the most occured data in a data set?

List<int> a = 11,2,3,11,3,22,9,2 //output 11 ...

Upgrading Enterprise Library (1.0) to LINQ or Entity framework

We are working on a C# windows project with enterprise library 1.0 that needs to be updated to either LINQ or Entity framework. (.NET 3.5) The application uses mainly SQL connections as stored procedures and XML files to store settings. What is the pros and cons with LINQ and Entity framework in this case? Are the rumors true that LI...

Linq To Sql - Update a value when another value changes

With Linq To Sql - what is the best way to update the value of one table in a database when a value changes in a different table? For example in TableA, there is a column called DateModified. TableA has an association to TableB. Now I want to set the value of the DateModified field to the current date every time the record changes in ta...

Simple (Dumb) LINQ Provider

Hi, How easy would it be to write a dumb LINQ provider that can just use my class definitions (which don't have any object references as properties) and give me the translated SQL. It can assume the name of the properties and the columns to be same as well as the names of the classes and the underlying tables. Can you please give me som...

Is there something wrong with my System.Xml.Linq library?

I'm trying to learn some Linq to XML stuff, and I came across the XPathSelectElement function in XElement. This function seems to do just what I need, but for some reason, I can't use it! Check out my code: XElement rootElement = XElement.Load(dataFile); XElement parentElement = rootElement.XPathSelectElement(xPath); ...

Using LINQ to SQL with Dynamic tables

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LINQ Optimization Question

So I've been using LINQ for a while, and I have a question. I have a collection of objects. They fall into two categories based on their property values. I need to set a different property one way for one group, and one way for the other: foreach(MyItem currentItem in myItemCollection) { if (currentItem.myProp == "CATEGORY_ONE"...

Is there an easy way to parse a (lambda expression) string into an Action delegate?

I have a method that alters an "Account" object based on the action delegate passed into it: public static void AlterAccount(string AccountID, Action<Account> AccountAction) { Account someAccount = accountRepository.GetAccount(AccountID); AccountAction.Invoke(someAccount); someAccount.Save(); } This works as intended... AlterAc...

Linq's OnValidate event doesn't get fired

I validate data for a table made in the linq designer in the event OnValidate. This event is fired when I insert records, but not is fired when I update records. I have this code: public bool Save(int id, string marca, string modelo, string año, string motor, bool disponible, RuleList issues) { Usado u; if (id == 0) { ...

Convert Dictionary<String,Int> to Dictionary<String,SomeEnum> using LINQ?

I'm trying to find a LINQ oneliner that takes a Dictionary<String,Int> and returns a Dictionary<String,SomeEnum>....it might not be possible, but would be nice. Any suggestions? EDIT: ToDictionary() is the obvious choice, but have any of you actually tried it? On a Dictionary it doesn't work the same as on a Enumerable... You can't pas...

LINQ: Remove items from IQueryable

I want to remove an item from the result of a LINQ query before using it to databind. What is the proper way to do this? The foreach in my illustration is the topic of my question. Illustration: var obj = (from a in dc.Activities where a.Referrer != null && a.Referrer.Trim().Length > 12 && a.Session.IP.NumProblems == 0...