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  • substring with linq??

    - by phenevo
    I've got collection of words, and i wanna create collection from this collection limited to 5 chars Input: Car Collection Limited stackoverflow Output: car colle limit stack word.Substring(0,5) throws exception (length) word.Take(10) is not good idea, too... Any good ideas ??

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  • Return an empty collection when Linq where returns nothing

    - by ahsteele
    I am using the below statement with the intent of getting all of the machine objects from the MachineList collection (type IEnumerable) that have a MachineStatus of i. The MachineList collection will not always contain machines with a status of i. At times when no machines have a MachineStatus of i I'd like to return an empty collection. My call to ActiveMachines (which is used first) works but InactiveMachines does not. public IEnumerable<Machine> ActiveMachines { get { return Customer.MachineList .Where(m => m.MachineStatus == "a"); } } public IEnumerable<Machine> InactiveMachines { get { return Customer.MachineList .Where(m => m.MachineStatus == "i"); } } Edit Upon further examination it appears that any enumeration of MachineList will cause subsequent enumerations of MachineList to throw an exeception: Object reference not set to an instance of an object. Therefore, it doesn't matter if a call is made to ActiveMachines or InactiveMachines as its an issue with the MachineList collection. This is especially troubling because I can break calls to MachineList simply by enumerating it in a Watch before it is called in code. At its lowest level MachineList implements NHibernate.IQuery being returned as an IEnumerable. What's causing MachineList to lose its contents after an initial enumeration?

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  • LINQ method chaining and granular error handling

    - by Clafou
    I have a method which can be written pretty neatly through method chaining: return viewer.ServerReport.GetParameters() .Single(p => p.Name == Convention.Ssrs.RegionParamName) .ValidValues .Select(v => v.Value); However I'd like to be able to do some checks at each point as I wish to provide helpful diagnostics information if any of the chained methods returns unexpected results. To achieve this, I need to break up all my chaining and follow each call with an if block. It makes the code a lot less readable. Ideally I'd like to be able to weave in some chained method calls which would allow me to handle unexpected outcomes at each point (e.g. throw a meaningful exception such as new ConventionException("The report contains no parameter") if the first method returns an empty collection). Can anyone suggest a simple way to achieve such a thing?

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  • linq merge elements with orderby

    - by Sanja Melnichuk
    Hi all. I need to select all terminals sorted by Attributes[2] // get all query IQueryable<ITerminal> itt = repository.Terminals.GetQuery(); // get all with Attributes[2] IQueryable<ITerminal> itt2 = itt .Select(item => new { attrs = item.Attributes[2], term = item }) .OrderBy(x => x.attrs) .Select(x => x.term); Now how to select from itt all terminals but ordered by itt2 results? How to order them by itt2? Example: itt = c,d,r,a,w,b itt2 = a,b,c // after select and after merge: a,b,c d,r,w Thanks all

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  • Linq to sql C# updating reference Tables

    - by Laurence Burke
    ok reclarification I am adding a new address and I know the structure as AddressID = PK and all other entities are non nullable. Now on insert of a new row the addrID Pk is autogened and I am wondering if I would have to get that to create a new row in the referencing table or does that automatically get generated also. also I want to be able to repopulate the dropdownlist that lists the current employee's addresses with the newly created address. static uint _curEmpID; protected void btnAdd_Click(object sender, EventArgs e) { if (txtZip.Text != "" && txtAdd1.Text != "" && txtCity.Text != "") { TestDataClassDataContext dc = new TestDataClassDataContext(); Address addr = new Address() { AddressLine1 = txtAdd1.Text, AddressLine2 = txtAdd2.Text, City = txtCity.Text, PostalCode = txtZip.Text, StateProvinceID = Convert.ToInt32(ddlState.SelectedValue) }; dc.Addresses.InsertOnSubmit(addr); lblSuccess.Visible = true; lblErrMsg.Visible = false; dc.SubmitChanges(); // // TODO: add reference from new address to CurEmp Table // SetAddrList(); } else { lblErrMsg.Text = "Invalid Input"; lblErrMsg.Visible = true; } } protected void ddlAddList_SelectedIndexChanged(object sender, EventArgs e) { lblErrMsg.Visible = false; lblSuccess.Visible = false; TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; if (ddlAddList.SelectedValue != "-1") { var addr = (from a in dc.Addresses where a.AddressID == Convert.ToInt32(ddlAddList.SelectedValue) select a).FirstOrDefault(); txtAdd1.Text = addr.AddressLine1; txtAdd2.Text = addr.AddressLine2; txtCity.Text = addr.City; txtZip.Text = addr.PostalCode; ddlState.SelectedValue = addr.StateProvinceID.ToString(); btnSubmit.Visible = true; btnAdd.Visible = false; } else { txtAdd1.Text = ""; txtAdd2.Text = ""; txtCity.Text = ""; txtZip.Text = ""; btnAdd.Visible = true; btnSubmit.Visible = false; } } protected void SetAddrList() { TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; var addList = from addr in dc.Addresses from eaddr in dc.EmployeeAddresses where eaddr.EmployeeID == _curEmpID && addr.AddressID == eaddr.AddressID select new { AddValue = addr.AddressID, AddText = addr.AddressID, }; ddlAddList.DataSource = addList; ddlAddList.DataValueField = "AddValue"; ddlAddList.DataTextField = "AddText"; ddlAddList.DataBind(); ddlAddList.Items.Add(new ListItem("<Add Address>", "-1")); } OK I am hoping that I did not include too much code. I would really appreciate any other comments about I could otherwise improve this code in any other ways also.

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  • LINQ Join 2 List<T>s

    - by David Murdoch
    Preface: I don't understand what this does: o => o.ID, i => i.ID, (o, id) => o So go easy on me. :-) I have 2 lists that I need to join together: // contains ALL contacts for a customer. // Each item has a unique ID. // There are no duplicates. ContactCollection list1 = myCustomer.GetContacts(); // contains the customer contacts (in list1) relevant to a REPORT // the items in this list may have properties that differ from those in list1. /*****/// e.g.: /*****/ bool SelectedForNotification; /*****/// may be different. ContactCollection list2 = myReport.GetContacts(); I need to create a third ContactCollection that contains all of the contacts in list1 but with the properties of the items in list2, if they are there (list3.Count == list1.Count). I feel as though I'm not making any sense. So, please ask questions in the comments and I'll try to clarify.

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  • Referencing object's identity before submitting changes in LINQ

    - by Axarydax
    Hi, is there a way of knowing ID of identity column of record inserted via InsertOnSubmit beforehand, e.g. before calling datasource's SubmitChanges? Imagine I'm populating some kind of hierarchy in the database, but I wouldn't want to submit changes on each recursive call of each child node (e.g. if I had Directories table and Files table and am recreating my filesystem structure in the database). I'd like to do it that way, so I create a Directory object, set its name and attributes, then InsertOnSubmit it into DataContext.Directories collection, then reference Directory.ID in its child Files. Currently I need to call InsertOnSubmit to insert the 'directory' into the database and the database mapping fills its ID column. But this creates a lot of transactions and accesses to database and I imagine that if I did this inserting in a batch, the performance would be better. What I'd like to do is to somehow use Directory.ID before commiting changes, create all my File and Directory objects in advance and then do a big submit that puts all stuff into database. I'm also open to solving this problem via a stored procedure, I assume the performance would be even better if all operations would be done directly in the database.

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  • Submitting changes to 2 tables with C# linq only one table is changing

    - by Laurence Burke
    SO I am changing the values in 2 different tables and the only table changing is the address table any one know why? protected void btnSubmit_Click(object sender, EventArgs e) { TestDataClassDataContext dc = new TestDataClassDataContext(); var addr = (from a in dc.Addresses where a.AddressID == Convert.ToInt32(ddlAddList.SelectedValue) select a).FirstOrDefault(); var caddr = (from ca in dc.CustomerAddresses where addr.AddressID == ca.AddressID select ca).FirstOrDefault(); if (txtZip.Text != "" && txtAdd1.Text != "" && txtCity.Text != "") { addr.AddressLine1 = txtAdd1.Text; addr.AddressLine2 = txtAdd2.Text; addr.City = txtCity.Text; addr.PostalCode = txtZip.Text; addr.StateProvinceID = Convert.ToInt32(ddlState.SelectedValue); caddr.AddressTypeID = Convert.ToInt32(ddlAddrType.SelectedValue); dc.SubmitChanges(); lblErrMsg.Visible = false; lblSuccess.Visible = true; } else { lblErrMsg.Text = "Invalid Input"; lblErrMsg.Visible = true; } }

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  • Using LINQ to remove dupicates in dictionary and the count of those duplicates

    - by Robert
    I have some code that returns unique elements in my dictionary, but I would also like to return the count of the duplicate elements. Basically change dictionary[key, uniqueelement] to dictionary[uniqueelement, count]. Here is my code that just returns the unique elements. var uniqueItems = deviceInstances.Children.GroupBy(pair => pair.Value.Information.UnderlyingDeviceType) .Select(group => group.First()) .ToDictionary(pair => pair.Key, pair => pair.Value.Information.UnderlyingDeviceType.ToString());

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  • Windows Azure Table Storage LINQ Operators

    - by Ryan Elkins
    Currently Table Storage supports From, Where, Take, and First. Are there plans to support any of the other 29 operators? If we have to code for these ourselves, how much of a performance difference are we looking at to something similar via SQL and SQL Server? Do you see it being somewhat comparable or will it be far far slower if I need to do a Count or Sum or Group By over a gigantic dataset? I like the Azure platform and the idea of cloud based storage. I like Windows Azure for the amount of data it can store and the schema-less nature of table storage. SQL Azure just won't work due to the high cost to storage space.

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  • Searching with Linq

    - by Phil
    I have a collection of objects, each with an int Frame property. Given an int, I want to find the object in the collection that has the closest Frame. Here is what I'm doing so far: public static void Search(int frameNumber) { var differences = (from rec in _records select new { FrameDiff = Math.Abs(rec.Frame - frameNumber), Record = rec }).OrderBy(x => x.FrameDiff); var closestRecord = differences.FirstOrDefault().Record; //continue work... } This is great and everything, except there are 200,000 items in my collection and I call this method very frequently. Is there a relatively easy, more efficient way to do this?

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  • Adding rows with linq trouble with reference table

    - by Laurence Burke
    I am adding a new address and I know the structure as AddressID = PK and all other entities are non nullable. Now on insert of a new row the addrID Pk is autogened and I am wondering if I would have to get that to create a new row in the referencing table EmployeeAddress or does that automatically get generated also. also I want to be able to repopulate the dropdownlist that lists the current employee's addresses with the newly created address. static uint _curEmpID; protected void btnAdd_Click(object sender, EventArgs e) { if (txtZip.Text != "" && txtAdd1.Text != "" && txtCity.Text != "") { TestDataClassDataContext dc = new TestDataClassDataContext(); Address addr = new Address() { AddressLine1 = txtAdd1.Text, AddressLine2 = txtAdd2.Text, City = txtCity.Text, PostalCode = txtZip.Text, StateProvinceID = Convert.ToInt32(ddlState.SelectedValue) }; dc.Addresses.InsertOnSubmit(addr); lblSuccess.Visible = true; lblErrMsg.Visible = false; dc.SubmitChanges(); // // TODO: insert new row in EmployeeAddress to reference CurEmp to newly created address // SetAddrList(); } else { lblErrMsg.Text = "Invalid Input"; lblErrMsg.Visible = true; } } protected void ddlAddList_SelectedIndexChanged(object sender, EventArgs e) { lblErrMsg.Visible = false; lblSuccess.Visible = false; TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; if (ddlAddList.SelectedValue != "-1") { var addr = (from a in dc.Addresses where a.AddressID == Convert.ToInt32(ddlAddList.SelectedValue) select a).FirstOrDefault(); txtAdd1.Text = addr.AddressLine1; txtAdd2.Text = addr.AddressLine2; txtCity.Text = addr.City; txtZip.Text = addr.PostalCode; ddlState.SelectedValue = addr.StateProvinceID.ToString(); btnSubmit.Visible = true; btnAdd.Visible = false; } else { txtAdd1.Text = ""; txtAdd2.Text = ""; txtCity.Text = ""; txtZip.Text = ""; btnAdd.Visible = true; btnSubmit.Visible = false; } } protected void SetAddrList() { TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; var addList = from addr in dc.Addresses from eaddr in dc.EmployeeAddresses where eaddr.EmployeeID == _curEmpID && addr.AddressID == eaddr.AddressID select new { AddValue = addr.AddressID, AddText = addr.AddressID, }; ddlAddList.DataSource = addList; ddlAddList.DataValueField = "AddValue"; ddlAddList.DataTextField = "AddText"; ddlAddList.DataBind(); ddlAddList.Items.Add(new ListItem("<Add Address>", "-1")); } OK I am hoping that I did not include too much code. I would really appreciate any other comments about I could otherwise improve this code in any other ways also.

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  • How to use linq to find the minimum

    - by Danvil
    I have a class A { public float Score; ... } and a List<A> items and would like to find the A which has minimal score. Using items.Min(x => x.Score) gives the minimal score and not the instance with minimal score. How can I get the instance with only iterating once through my Collection?

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  • LINQ Query returns nothing.

    - by gtas
    Why is this query returns 0 lines? There is a record matching the arguments. Deafkaw.Where(p => (p.ImerominiaKataxorisis >= aDate && p.ImerominiaKataxorisis <= DateTime.Now) && (p.Year == etos && p.IsYpodeigma == false) ).ToList(); Am i missing something?

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  • Dynamic Linq query issue

    - by Alex
    Hey All, Im trying to query the Netflix OData feed. I have the following query that works fine in LinqPad: from g in Genres from t in g.Titles where g.Name == "Horror" && t.AverageRating == 2 && t.ReleaseYear == 2004 select t But, when I move it over to my Silverlight app, the user selects what to search on so I may or may not have all of the params. That being the case, I need to construct the query at runtime. Ive looked the the Dynamic Query stuff and that will do fine...the issue that I have is that I need an initial acceptable query to append to and this doesn't fly: from g in Genres from t in g.Titles select t; Any additional thoughts would be appreciated. Thanks in advance

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  • linq expression in vb.net

    - by Thurein
    Hi, Can any body translate the following c# code to vb. I have tried telarik code converter but I got problem at expression.call and it won't compile at all. private static IOrderedQueryable<T> OrderingHelper<T>(IQueryable<T> source, string propertyName, bool descending, bool anotherLevel) { ParameterExpression param = Expression.Parameter(typeof(T), string.Empty); MemberExpression property = Expression.PropertyOrField(param, propertyName); LambdaExpression sort = Expression.Lambda(property, param); MethodCallExpression call = Expression.Call( typeof(Queryable), (!anotherLevel ? "OrderBy" : "ThenBy") + (descending ? "Descending" : string.Empty), new[] { typeof(T), property.Type }, // error line source.Expression, Expression.Quote(sort)); return (IOrderedQueryable<T>)source.Provider.CreateQuery<T>(call); } thanks Thurein

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  • How to bind gridview using linq/Entity Framework?

    - by Kay
    I need to bind GridView, I am using this code: ProductDBEntities db = new ProductPDBEntities(); var pro = from u in db.Products where u.PID == 1 select u; if (pro != null) { GridView1.DataSource = pro; GridView1.DataBind(); } and getting this error. System.InvalidOperationException: Sequence contains more than one element Can somebody please tell me what am I doin wrong?

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  • LINQ to SQL: On load processing of lazy loaded associations

    - by Matt Holmes
    If I have an object that lazy loads an association with very large objects, is there a way I can do processing at the time the lazy load occurs? I thought I could use AssociateWith or LoadWith from DataLoadOptions, but there are very, very specific restrictions on what you can do in those. Basically I need to be notified when an EntitySet< decides it's time to load the associated object, so I can catch that event and do some processing on the loaded object. I don't want to simply walk through the EntitySet when I load the parent object, because that will force all the lazy loaded items to load (defeating the purpose of lazy loading entirely).

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  • Comparison operators not supported for type IList when Paging data in Linq to Sql

    - by Dan
    I can understand what the error is saying - it can't compare a list. Not a problem, other than the fact that I don't know how to not have it compare a list when I want to page through a model with a list as a property. My Model: Event : IEvent int Id string Title // Other stuff.. LazyList<EventDate> Dates // The "problem" property Method which pages the data (truncated): public JsonResult JsonEventList(int skip, int take) { var query = _eventService.GetEvents(); // Do some filtering, then page data.. query = query.Skip(skip).Take(take); return Json(query.ToArray()); } As I said, the above is truncated quite a bit, leaving only the main point of the function: filter, page and return JSON'd data. The exception occurs when I enumerate (.ToArray()). The Event object is really only used to list the common objects of all the event types (Meetings, Birthdays, etc - for example). It still implements IEvent like the other types, so I can't just remove the LazyList<EventDate> Dates' property unless I no longer implementIEvent` Anyway, is there a way to avoid this? I don't really want to compare a LazyList when I page, but I do not know how to resolve this issue. Thank you in advance! :)

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  • linq to sql loadwith vs associatewith

    - by stackoverflowuser
    what is the difference between loadwith and associatewith. From the articles i read it seems that loadwith is used to load addition data (eg all orders for the customers). While AssociateWith is used to filter data. Is that a correct understanding? Also it will be nice if someone can explain this with an example based explanation.

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  • Linq DateTime expressions wont compare if only one is nullable

    - by tigermain
    I have been getting the following exception: The binary operator GreaterThanOrEqual is not defined for the types 'System.Nullable`1[System.DateTime]' and 'System.DateTime'. I am getting the left hand expression from a class property which is a nullable datetime variable and my right hand side is using Expression.Constant(new Nullable<DateTime>(DateTime.Now)) However I still get the above exception despite explicitly setting the right hand expression to a nullable type

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  • DB4o Linq query - How to check for null strings

    - by Dave
    Hey there - simple query: var q = (from SomeObject o in container where o.SomeInt > 8 && o.SomeString != null //Null Ref here select o; I always get a null reference exception. If I use String.IsNullOrEmpty(o.SomeString) the query takes about 100 times as long, as if I use && o.SomeString != "" (which is way faster, but obviously not correct). I'm guessing because DB4o needs to activate the objects, in order to pass them in to the IsNullOrEmpty call, and can't use the indexes. My question is, what's a better way to check for nulls in this situation? Is there something like: mystring != Db4o.DBNull.Value, or something? Cheers, Dave

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  • LINQ query null reference exception

    - by user289082
    Hi! I have the next query: var bPermisos = from b in ruc.Permisos where b.IdUsuario == cu.Id select new Permisos(){ Id=b.Id, IdUsuario=b.Id, IdPerfil=b.Id, Estatus=b.Estatus }; var qSisPer = from perm in bPermisos select new { perm.IdPerfil,perm.Cat_Perfil.Nivel,perm.Cat_Perfil.Nombre,Nombre_Sistem=perm.Cat_Perfil.Cat_Sistema.Nombre}; And is throwing me an exception, plz help!

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  • linq multiple order DESCENDING

    - by ile
    .OrderBy(y => y.Year).ThenBy(m => m.Month); How to set descending order? EDIT: I tried this: var result = (from dn in db.DealNotes where dn.DealID == dealID group dn by new { month = dn.Date.Month, year = dn.Date.Year } into date orderby date.Key.year descending orderby date.Key.month descending select new DealNoteDateListView { DisplayDate = date.Key.month + "-" + date.Key.year, Month = date.Key.month, Year = date.Key.year, Count = date.Count() }) //.OrderBy(y => y.Year).ThenBy(m => m.Month) ; And it seems working. Is it wrong to use orderby twice like I used it here?

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  • LINQ to SQL: making a "double IN" query crashes

    - by Alex
    I need to do the following thing: var a = from c in DB.Customers where (from t1 in DB.Table1 where t1.Date >= DataTime.Now select t1.ID).Contains(c.ID) && (from t2 in DB.Table2 where t2.Date >= DataTime.Now select t2.ID).Contains(c.ID) select a It doesn't want to run. I get the following error: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. But when I try to run var a = from c in DB.Customers where (from t1 in DB.Table1 where t1.Date >= DataTime.Now select t1.ID).Contains(c.ID) select a OR var a = from c in DB.Customers where (from t2 in DB.Table2 where t2.Date = DataTime.Now select t2.ID).Contains(c.ID) select a It works! I'm sure that there both IN queries contain some customers ids.

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