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  • VB.NET logical expression evaluator

    - by Tim
    I need to test a logical expression held in a string to see if it evaluate to TRUE or FALSE.(the strig is built dynamically) For example the resulting string may contain "'dog'<'cat' OR (14 AND 4<6)". There are no variables in the string, it will logically evaluate. It will only contain simple operators = < < = <= and AND , OR and Open and Close Brackets, string constants and numbers. (converted to correct syntax && || etc.) I currently acheive this by creating a jscipt function and compiling it into a .dll. I then reference the .dll in my VB.NET project. class ExpressionEvaluator { function Evaluate(Expression : String) { return eval(Expression); } } Is there a simpler method using built in .NET functions or Lamdba expressions.

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  • Is it possible to load an entire SQL Server CE database into RAM?

    - by DanM
    I'm using LinqToSql to query a small SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table via a foreign key, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of the appeal of LinqToSql. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view.

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  • What does P mean in Sort(Expression<Func<T, P>> expr, ListSortDirection direction)?

    - by Grasshopper
    I am attempting to use the answer in post: How do you sort an EntitySet<T> to expose an interface so that I can sort an EntitySet with a Binding list. I have created the class below and I get the following compiler error: "The type or namespace 'P' could not be found (are you missing a using directive or assembly reference?). Can someone tell me what the P means and which namespace I need to include to get the method below to compile? I am very new to delegates and lamba expressions. Also, can someone confirm that if I create a BindingList from my EntitySet that any modifications I make to the BindingList will be made to the EntitySet? Basically, I have an EntitySet that I need to sort and make changes to. Then, I will need to persist these changes using the original Entity that the BindingList came from. public class EntitySetBindingWrapper<T> : BindingList<T> { public EntitySetBindingWrapper(BindingList<T> root) : base(root) { } public void Sort(Expression<Func<T, P>> expr, ListSortDirection direction) { if (expr == null) base.RemoveSortCore(); MemberExpression propExpr = expr as MemberExpression; if (propExpr == null) throw new ArgumentException("You must provide a property", "expr"); PropertyDescriptorCollection descriptorCol = TypeDescriptor.GetProperties(typeof(T)); IEnumerable<PropertyDescriptor> descriptors = descriptorCol.Cast<PropertyDescriptor>(); PropertyDescriptor descriptor = descriptors.First(pd => pd.Name == propExpr.Member.Name); base.ApplySortCore(descriptor, direction); } }

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  • Cannot perform an ORDERBY against my EF4 data

    - by Jaxidian
    I have a query hitting EF4 using STEs and I'm having an issue with user-defined sorting. In debugging this, I have removed the dynamic sorting and am hard-coding it and I still have the issue. If I swap/uncomment the var results = xxx lines in GetMyBusinesses(), my results are not sorted any differently - they are always sorting it ascendingly. FYI, Name is a varchar(200) field in SQL 2008 on my Business table. private IQueryable<Business> GetMyBusinesses(MyDBContext CurrentContext) { var myBusinesses = from a in CurrentContext.A join f in CurrentContext.F on a.FID equals f.id join b in CurrentContext.Businesses on f.BID equals b.id where a.PersonID == 52 select b; var results = from r in myBusinesses orderby "Name" ascending select r; //var results = from r in results // orderby "Name" descending // select r; return results; } private PartialEntitiesList<Business> DoStuff() { var myBusinesses = GetMyBusinesses(); var myBusinessesCount = GetMyBusinesses().Count(); Results = new PartialEntitiesList<Business>(myBusinesses.Skip((PageNumber - 1)*PageSize).Take(PageSize).ToList()) {UnpartialTotalCount = myBusinessesCount}; return Results; } public class PartialEntitiesList<T> : List<T> { public PartialEntitiesList() { } public PartialEntitiesList(int capacity) : base(capacity) { } public PartialEntitiesList(IEnumerable<T> collection) : base(collection) { } public int UnpartialTotalCount { get; set; } }

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  • Textbox is disabled after adding text dynamically in codebehind

    - by user1761348
    Can't quite work out what is happening but The background is that I am dynamically adding table rows in a web page and some of the cells hold controls such as dropdowns etc. One of the columns pulls a size into it. However the column I am having issues with is the next column which takes the text from teh previous dropdown and shows the appropriate price. On doing htis however the textbox which is being created appears to turn into a label as I cannot select or adjust the text that has been put in there. var gotPrice =(from a in getPrice.Sizes where a.Size1 == Size.SelectedValue select a).First(); TextBox Price = new TextBox(); Price.Width = 100; PriceField.Controls.Add(Price); PriceField.Text = gotPrice.RackRate.ToString(); I have tried then calling .Enabled but still the text box is not editable. any help appreciated.

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  • removing items from a generic List<t>

    - by frosty
    I have the following method, I wish to remove items from my collection that match the product Id. Seems fairly straight forward, but i get an exception. Basically my collection is getting out of sync. So what is the best way to remove an item from a collection. public void RemoveOrderItem(Model.Order currentOrder, int productId) { foreach (var orderItem in currentOrder.OrderItems) { if (orderItem.Product.Id == productId) { currentOrder.OrderItems.Remove(orderItem); } } } Exception Details: System.InvalidOperationException: Collection was modified; enumeration operation may not execute

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  • Entity framework 4.0 compiled query with Where() clause issue

    - by Andrey Salnikov
    Hello, I encountered with some strange behavior of System.Data.Objects.CompiledQuery.Compile function - here is my code for compile simple query: private static readonly Func<DataContext, long, Product> productQuery = CompiledQuery.Compile((DataContext ctx, long id) => ctx.Entities.OfType<Data.Product>().Where(p => p.Id == id) .Select(p=>new Product{Id = p.Id}).SingleOrDefault()); where DataContext inherited from ObjectContext and Product is a projection of POCO Data.Product class. My data context in first run contains Data.Product {Id == 1L} and in second Data.Product {Id == 2L}. First using of compilled query productQuery(dataContext, 1L) works perfect - in result I have Product {Id == 1L} but second run productQuery(dataContext, 2L) always returns null, instead of context in second run contains single product with id == 2L. If I remove Where clause I will get correct product (with id == 2L). It seems that first id value caching while first run of productQuery, and therefore all further calls valid only when dataContext contains Data.Product {id==1L}. This issue can't be reproduced if I've used direct query instead of its precompiled version. Also, all tests I've performed on test mdf base using SQL Server 2008 express and Visual studio 2010 final from my ASP.net application.

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  • Merging ILists to bind on datagridview to avoid using a database view

    - by P.Bjorklund
    In the form we have this where IntaktsBudgetsType is a poorly named enum that only specifies wether to populate the datagridview after customer or product (You do the budgeting either after product or customer) private void UpdateGridView() { bs = new BindingSource(); bs.DataSource = intaktsbudget.GetDataSource(this.comboBoxKundID.Text, IntaktsBudgetsType.PerKund); dataGridViewIntaktPerKund.DataSource = bs; } This populates the datagridview with a database view that merge the product, budget and customer tables. The logic has the following method to get the correct set of IList from the repository which only does GetTable<T>.ToList<T> public IEnumerable<IntaktsBudgetView> GetDataSource(string id, IntaktsBudgetsType type) { IList<IntaktsBudgetView> list = repository.SelectTable<IntaktsBudgetView>(); switch (type) { case IntaktsBudgetsType.PerKund: return from i in list where i.kundId == id select i; case IntaktsBudgetsType.PerProdukt: return from i in list where i.produktId == id select i; } return null; } Now I don't want to use a database view since that is read-only and I want to be able to perform CRUD actions on the datagridview. I could build a class that acts as a wrapper for the whole thing and bind the different table values to class properties but that doesn't seem quite right since I would have to do this for every single thing that requires "the merge". Something pretty important (and probably basic) is missing the the thought process but after spending a weekend on google and in books I give up and turn to the SO community.

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  • check existense between two IEnumerable

    - by sunglim
    IEnumerable<String> existedThings = from mdinfo in mdInfoTotal select mdinfo.ItemNo; IEnumerable<String> thingsToSave = from item in lbXReadSuccess.Items.Cast<ListItem>() select item.Value; Here are two IEnumerable. I want to check whether a value in existedThings exist in thingsToSave. O.K. I can do that with 3 line code. bool hasItemNo; foreach(string itemNo in existedThings) hasItemNo= thingsToSave.Contains(itemNo); But, It looks dirty. I just want to know if there better solution.

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  • ASP.NET MVC DataAnnotations different tables. Can it be done?

    - by mazhar kaunain baig
    i have a language table which is as a foreign key in the link table , The link can be in 3 languages meaning there will be 3 rows in the link table every time i enter the record . i am using jQuery tabs to enter the records in 3 languages . OK so that thing is that there will be three text boxes for every field in the table.link name field will have 3 text boxes, description will have 3 text boxes and so on. i am using LINK to SQL with VS2010. i will be creating link class with MetadataType so how will i handle for eg link name attribute 3 times

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  • Adding LambaExpression to an instance of IQueryable

    - by Paul Knopf
    ParameterExpression parameter = Expression.Parameter(typeof(Product), "x"); MemberExpression Left = Expression.MakeMemberAccess(parameter, typeof(Product).GetProperty("Name")); ConstantExpression Right = Expression.Constant(value, typeof(String)); BinaryExpression expression = Expression.Equal(Left, Right); LambdaExpression lambada = Expression.Lambda<Func<Product, bool>>(expression, parameter); Now how do I add this lambada to an instance of an IQuerybale, lets say _query _query.Where(lambada.Compile());?

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  • How to do rolling balances in Linq2SQL

    - by David Liddle
    Given an account with a list of transactions I would like to output a query that shows each transaction with the rolling balance (just like you would see on an online banking account). TRANSACTIONS - ID - DATE - AMOUNT Here is what I created in T-SQL however was wondering if this can be translated to linq2sql code? select T.ID, convert(char(10), T.DATE, 101) as 'DATE', T.AMOUNT, (select sum(O.AMOUNT) from TRANSACTIONS O where O.DATE < T.DATE or (O.DATE = T.DATE and O.ID <= T.ID)) 'BALANCE' from TRANSACTIONS as T where T.DATE between @pStartDate and @pEndDate order by T.DATE, T.ID Alternatively I guess my other option is to just call a stored procedure for these kind of results. However, I have Services which call Repositories and didn't really want to put the sproc call in the Repository.

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  • Accessing child collection in query

    - by Gokul
    I am populating a list using List<Country> countries = new List<Country> { new Country() { CountryID = "US", City = new List<City> { new City() { CountryID = "US", CityName="dfdsf", sqkm = 2803 } } }; and so on How to access sqkm in the following query? var countryQuery = countries .Select(c => new { Id = c.CountryId, Area = c.City.sqkm???}); c.city.sqkm gives compilation error...how to modify query

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  • Bit convector : Get byte array from string

    - by nCdy
    When I have a string like "0xd8 0xff 0xe0" I do Text.Split(' ').Select(part => byte.Parse(part, System.Globalization.NumberStyles.HexNumber)).ToArray(); But if I got string like "0xd8ffe0" I don't know what to do ? also I'm able for recommendations how to write byte array as one string.

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  • ASP.NET MVC Inserting object and related object into 2 tables

    - by ile
    I have two tables: Users and UserOwners. Table UserOwners contains list of users that certain user created (list of child-users) - or to be more precise, it contains UserOwnerID and UserID fields. So, now I want to create a new user... in Controller I have something like this: var userOwner = accountRepository.GetUser(User.Identity.Name); var userOwnerID = userOwner.UserID; UserReference userReference = new UserReference(); userReference.UserOwnerID = userOwnerID; if (ModelState.IsValid) { try { //accountRepository.Add(user); //accountRepository.Save(); return View(); } catch { return View(); } } What is the easiest way to add new user to a table Users and matching UserOwner to UserOwners table. Is it suppose to be something like this? public void Add(User user) { db.Users.InsertOnSubmit(user); db.UserReferences.InsertOnSubmit(user.UserReference); } ...or I will have to pass two objects and after adding user I must read it's ID and than assign it to userReference object and add that object to DB? If so, how to read ID of the last object added? Thanks, Ile

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  • How can I check the type of an object against a list of types?

    - by RookieRick
    Given a collection IEnumerable<Type> supportedTypes What's the best way to check whether a given object is one of those types (or a derived type)? My first instinct was to do something like: // object target is a parameter passed to the method in which I'm doing this. if (supportedTypes.Count( supportedType => target is supportedType ) > 0) { // Yay my object is of a supported type!!! } ..but that doesn't seem to be working. Can I not use the "is" keyword in a lambda expression like this?

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  • How do I use XPath with a default namespace with no prefix?

    - by Scott Stafford
    What is the XPath (in C# API to XDocument.XPathSelectElements(xpath, nsman) if it matters) to query all MyNodes from this document? <?xml version="1.0" encoding="utf-8"?> <configuration> <MyNode xmlns="lcmp" attr="true"> <subnode /> </MyNode> </configuration I tried /configuration/MyNode which is wrong because it ignores the namespace. I tried /configuration/lcmp:MyNode which is wrong because lcmp is the URI, not the prefix. I tried /configuration/{lcmp}MyNode which failed because Additional information: '/configuration/{lcmp}MyNode' has an invalid token. EDIT: I can't use mgr.AddNamespace("df", "lcmp"); as some of the answerers have suggested. That requires that the XML parsing program know all the namespaces I plan to use ahead of time. Since this is meant to be applicable to any source file, I don't know which namespaces to manually add prefixes for. It seems like {my uri} is the XPath syntax, but Microsoft didn't bother implementing that... true?

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  • Entity Framework 5 upgrade from 4

    - by user1714591
    I'm having an issue with the Where clause in a search, in my original version EF4 I could add a Where clause with 2 parameters, the where clause (string predicate) and a ObjectParameter list such as var query = context.entities.Where(WhereClause.ToString(), Params.ToArray()); since my upgrade to EF5 I don't seem to have that option am I missing something? This was originally used to build dynamic where clause such as "it.entity_id = @entity_id" then holding the variable value in the ObjectParameter. I'm hoping I don't have to rewrite all the searches that have been built out this way, so any assistance would be greatly appreciated. Cheers

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