Entity Framework Core - Knowledge Base (KB)
26 results in tag: lambda
Use method in entity framework query
Is there anyway around this error? I'd like to reuse the same lamba expression in other queries instead of having duplication. Can LinqKit or other linq expression do this?...Error...LINQ to Entities does not recognize the method 'Boolean GetEvent(Tournam...
asked by Mike Flynn
EF Core helper method for explicit loading references and collections
EF Core has support for ...explicit loading.... The context has two overloads, one for references and one for collections....Having two methods is not useful, and gets messy. I want a single method for accepting both as a params array....So instead of thi...
asked by grokky
Entity Framework combine lambda expressions from different entities
I have 2 lambda expressions that are virtually the same. One returns ...Expression<Func<Person, bool>>... and the other returns ...Expression<Func<Admission, bool>>.......There is a direct relationship between these 2 entities. A ...Person... can have man...
asked by Gwasshoppa
How to write Repository method for .ThenInclude in EF Core 2
I'm trying to write a repository method for Entity Framework Core 2.0 that can handle returning child collections of properties using .ThenInclude, but I'm having trouble with the second expression. Here is a working method for .Include, which will return...
asked by redwards510
How to pass lambda 'include' with multiple levels in Entity Framework Core?
I have a repository that gets a lambda expression for 'include'. ...public TEntity FirstOrDefault(Expression<Func<TEntity, bool>> predicate, params Expression<Func<TEntity, object>>[] includePaths) { return Context.Set<TEntity>().Includes(incl...
asked by Igor
Custom Sorting using c# Linq Expressions
I'm trying to make sorting easier for an C# Application and C# Web API. I'm using Entity Framework Core for my persistence and testing....In my application or Web API I determine the Order, Descending or Ascending, Property Name....I pass this knowledge ...
asked by chris31389
Store Lambda expressions as variable
Is it possible to store a lambda expression as a variable and use it in multiple places. My db objects have an ...Id... as int and a ...UId... as an uniqueidentifier and I have to write very similar expressions when selecting based on ...Id... or ...UId..
asked by Stein The Ruler
Reusing Lambda Select Fragments in LINQ
I would like to be able to reuse ...fragments... of my select lambda expressions in my Entity Framework Core 2.0 queries. ...For example:...var result = await ctx.Customers .Select(cust => new CustomerDto { CustomerId = cust.Id, CustomerName = ...
asked by Neilski
How To create linq Expression dynamically in c# for Contains
I am trying to create expression dynmically but i could not figure it out... Also dont want to use like this.....if (item.id == 1) filter.AddExpression(c => filterValues.Contains(c.a1)); if (item.id == 2) filter.AddExpression(c => filterValues.Contains(c....
asked by kanpinar
How can I implement a LEFT OUTER JOIN in LINQ using lambda syntax on Entity Framework Core 2.0?
I am trying to implement a LEFT OUTER JOIN in Linq against an Entity Framework Core 2.0 DbContext. It's important that the query is translated to SQL, rather than evaluated locally. I've reviewed several StackOverflow solutions including ...this one... ...
asked by Peter
Nested Expression method call in Linq.Select()
I use ....Select(i=> new T{...})... after every db hit manually to convert my entity objects into DTO object. Here are some sample entities and DTOS...User Entity;...public partial class User { public int Id { get; set; } public string Username { ...
asked by ilkerkaran
How to create a Stuff and XML PATH(SQL) in Linq or Lambda
How to create the equivalent code in Linq or lambda?...I'm using Entity Framework Core on Asp.net Core 2....SELECT (SELECT STUFF((SELECT DISTINCT ', ' + Roles.Name FROM AspNetUsers Users INNER JOIN AspNetUser...
asked by Leonardo Pavanello
Include the IsDeleted values when user is admin
I want to include the ...isDeleted... values in the database to my index when the user is an admin. I used the global query filter to filter the data. ...This is the code I have:...var param = Expression.Parameter(entity.ClrType); var propertyMethodInfo ...
asked by darwin
Combine BinaryExpression and Expression<Func<dynamic, bool>> in C#
How can I combine ...BinaryExpression... and ...Expression<Func<dynamic / T, bool>>...?...For example:...void AddGlobalFilter<T>(Expression<Func<T, bool>> expr) { var parameter = Expression.Parameter(type, "t"); var member = Expression.Property(fi...
asked by Makla
Dynamic query filter expression in include
i am working with the entity framework core HasQueryFilter method while having a dynamic variable within this filter expression. Because of this dynamic parameter (lets name it "MinPriority") i cannot directly pass a lambda expression like...HasQueryFilte...
asked by cyptus
How to create "inline if statement" with expressions in dynamic select for null checking
How to create "inline if statement" with expressions in dynamic select for null checking ...I was wrote a dynamic linq select expression for a nested property of a object, but it throw an exception when it is null. so i want to check whether that property...
asked by Mohammad
Group Join Select With Comma Separated
I have a query Like below in .net Core 2.2 with EF....var data = context.Customer .GroupJoin(context.Orders, c=> c.Id, o => o.CustoerId, (c, o) => new { customer = c, ...
asked by AKASH
Modifying an Entity Framework expression when tables have been remapped
I have an issue now that a table has had an id removed....First I had this query below where entity (table) 'RecordsProduct' has a 'DefendnatId' that was mapped to a Defendant table. It was fine! ... records = records .Include(r...
asked by user1186050
Re-implementation of OrderBy, ThenBy and Null TypeMapping in Sql Tree error
I am trying to implement ...OrderBy... and ...ThenBy... in a different way to hide lambda expression from ...OrderBy... and ...ThenBy... extension methods. These extension methods accept classes which implement ...IOrderSpecification...: ...public class P...
asked by peyman gilmour
C# Entity Framework Core Conditional Projection
I currently use Entity Framework Core, and it works really well. However, one things I am trying to optimise in my application is returning computed data from the database at the time of querying. I am using code first, where each model directly maps to a...
asked by Eliott Robson