Expression Tree Tutorial - Knowledge Base (KB)
656 results
Building dynamic lambda expressions
I know how to build a simple lambda like ...x => x > 5...:...int[] nbs = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; IEnumerable<int> result1 = nbs.Where(x => x > 5); ParameterExpression parameter = Expression.Parameter(typeof(int), "x"); Consta...
asked by Andy Rehn
Building dynamic lambda expression
I know how to build a simple lambda like ...x => x > 5...:...int[] nbs = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; IEnumerable<int> result1 = nbs.Where(x => x > 5); ParameterExpression parameter = Expression.Parameter(typeof(int), "x"); Consta...
asked by Andy Rehn
Building lambda expression dynamically
I know how to build a simple lambda like x => x > 5:...int[] nbs = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; IEnumerable<int> result1 = nbs.Where(x => x > 5); ParameterExpression parameter = Expression.Parameter(typeof(int), "x"); ConstantExpr...
asked by Andy Rehn
DateTime lambda expressions
I was testing the implementation in the thread answer ...https://stackoverflow.com/a/7891426/1468492... but I get an error trying to parse an expression with a ...DateTime..., for instance: ...t => t.Name == "NAME" && t.OpeningDate == DateTime.Now.... ...
asked by Ernesto Rodriguez
Write Dynamic LINQ queries for sorting and projecting with EF Core
I am having troubles trying to get valid expressions for "inner graph" members....I wrote several code lines based on previous stack overflow answers. but I have issues finding a good "solution approach"....For example trying to express "a string" as a la...
asked by alhpe
How to extract a where clause expression tree from IQueryable
I need to add an "Or" clause in a where clause dynamically, depending on some conditions to an existing IQueryable object. ...Using ExpressionBuilder, I can compose a left and right Expression> but for that to wrok, I need to extract the Expression> from ...
asked by Stéphan
Text query parsing in Sprache
I'm trying to write some code to match strings based on a pattern:...pattern: "dog and (cat or goat)" ...test string: "doggoat" result: true...test string: "dogfrog" result: false...I'm trying to write a parser using Sprache, with most of the logic provid...
asked by Alan Sage
Accessing expression bodied members to build expression trees
Trying to build an order by expression using expression trees. But I am unable to access an expression bodied property of the query result's class. This is the class structure:...public class AssetFileRecord : IAuditable, IEntity, INavigateToCustomValues ...
asked by Abhay Nagaraj
Entity Framework Core- Use Expression Tree With Interface As Parameter
I will really appreciate some help with following scenario. I have the following classes:...public class Product : IHasPrice { public string Title { get; set; } public int Price { get; set; } public string CustomerId { get; set; } } public i...
asked by Tal Humy
System.Linq.Dynamic.DynamicExpression parsing expressions with enum parameters
I am trying to parse a LambdaExpression Tree using DynamicExpression.ParseLambda but I cannot get it to correctly parse when using string.Equals with the StringComparison enum....I have tried:...a) using StringComparison but I get the error 'Unknown ident...
asked by Rossimac
EF Core SQL Function LIKE Method with Linq Expression not working for Non String types
am able to create an invoke Expression with SQL Functions like as shown below...var likeMethod = typeof(DbFunctionsExtensions).GetMethod("Like", new[] { typeof(DbFunctions), typeof(string), typeof(string) }); Expression.Call(null, likeMethod, Expression....
asked by Akshay Joy
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
Complex edit of a body Expression<Func<T,bool>>
Summary:... I want to know how can I detect specific definitions from the expression's body then change it in the way I want, such as ...e.Entity.ListA.Union(e.ListB).Any(...)... ...To...e.Entity != null && ((e.Entity.ListA != null && e.Entity.ListA.Any(...
asked by AbuDawood
Correct Collection in ConstantExpression for EF Core
I try to realize my own Expression serializator/deserializator for passing it through services (I want to realize my own endpoint for EF Core service). So, now I have problem with Collections in LambdaExpressions. For example,...var dataQuery = testDb.Use...
asked by Dmitriy
Conditionally ignore fields with LINQ select
I've been unable to find any examples where you can conditionally exclude fields based off a variable within a select projection in LINQ, see also ...LINQ: Select an object and change some properties without creating a new object.......Let me give some ba...
asked by Mark G
Entity Framework Core LINQ Tree Expression Problem with Concat
So I have a IQueryable extension that does a little more than this block of code. Essentially I'm combining of bunch of strings and afterwards doing a Contains on them. The problem I'm running into is that Entity Framework Core doesn't support System.Stri...
asked by Richard Cawthon
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