linq-expressions

I have the following method SetMapping() which is used to define some mapping setting using expressions. public class AggregateMap<TDataEntity> { protected Expression<Func<IUpdateConfiguration<TDataEntity>, object>> graphMapping; protected void SetMapping(Expression<Func<IUpdateConfiguration<TDataEntity>, object>> mapping) { graphMapping = mapping; } } Example calling code: SetMapping(map => map.OwnedCollection(root => root.ChildEntities)); The above works great, but I would like to abstract this method a bit further by providing SetOwnedCollectionMapping() . This means the calling code can

This question already has an answer here: Combining two expressions (Expression<Func<T, bool>>) 6 answers I'm in the process of refactoring some code, attempting to make it more self-documenting. The current code has a query over an OData service which looks like this: return context.MessageLog.Where ( x => ( x.Status == MessageStatus.Success || x.Status == MessageStatus.Failure ) && x.Direction == MessageDirection.Inbound && x.ResponseDate == new DateTimeOffset(new DateTime(1900, 01, 01)) ); I'm hoping to change this to make use of Linq Expressions. I could move all of the logic into a single

I am trying to create an extension "WhereNot" So I can use: Dim x = "Hello world " Dim y = x.Split.WhereNot(AddressOf String.IsNullOrEmpty) Note that my aim here is to learn linq expressions; not solve my issue. I craated this function: <Extension()> _ Public Function WhereNot(Of TElement)(ByVal source As IQueryable(Of TElement), ByVal selector As Expression(Of Func(Of TElement, Boolean))) As IQueryable(Of TElement) Return source.Where(GetWhereNotExpression(selector)) End Function I don't know how to switch the boolean flag, will the function Negate do it? answers in both vb.net and C# are

I have a generic method in which I want to sort an IQueryable<T> by its key field (it is safe to assume there is only one). Thus: void DoStuff<T>(...) { IQueryable<T> queryable = ... // given PropertyInfo keyField = ... // given var sortedQueryable = queryable.OrderBy(<some expression here>); ... } How do I define an Expression that will return the keyField property of T so that this will work? This isn't too difficult, but you need to invoke the OrderBy with reflection as you don't know the type of the key field ahead of time. So given the code you already show, you would do something like

I just want to make Column Filter for grid view. Simple I just want to filter grid view column with some extra stuff. Here I have created one IQueryable that returns queryable result. Here is my code : ------------------------------------------Updated------------------------------------------------ public static IQueryable<T> FilterForColumn<T>(this IQueryable<T> queryable, string colName, string searchText) { if (colName != null && searchText != null) { var parameter = Expression.Parameter(typeof(T), "m"); var propertyExpression = Expression.Property(parameter, colName); System.Linq

I am using patterns mentioned here http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application And i am using method below to query EF public virtual IEnumerable<TEntity> Get( Expression<Func<TEntity, bool>> filter = null, Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null, string includeProperties = "") { IQueryable<TEntity> query = dbSet; if (filter != null) { query = query.Where(filter); } foreach (var includeProperty in includeProperties.Split (new char[] { ',' }, StringSplitOptions

Has any work been done on the direct conversion of CIL to LINQ expression trees? This would include class libraries, blogs, books, academic papers, etc. What are the known mismatches between CIL and LINQ Expression API? I have seen a project that significantly extended the Expression API to support an almost complete mapping between C# and LINQ Expressions. What work arounds would be suggested to accommodate any of these mismatches? Is there something fundamentally wrong about converting directly from CIL to LINQ Expressions? If so, why? 来源： https://stackoverflow.com/questions/12824201/how-to

I want to combine two LambdaExpressions without compiling them. This is what it looks like if I do compile them: public Expression<Func<TContainer,bool>> CreatePredicate<TContainer,TMember>( Expression<Func<TContainer,TMember>> getMemberExpression, Expression<Func<TMember,bool>> memberPredicateExpression) { return x => memberPredicateExpression.Compile()(getMemberExpression.Compile()(x)); } That's obviously not the fastest way to get the target expression from the provided arguments. Also, it makes it incompatible with query providers like LINQ to SQL that do not support C# method calls. From