608 questions
0
votes
1
answer
57
views
Pass ModelExpression for use in asp-for tag helper in Razor Pages [duplicate]
I have some repeated code I'd like to move to a Razor Pages code block, which contains an asp-for tag helper. That expects a ModelExpression, and I'm unsure how to pass that.
@model IndexModel
@{
...
- 21.5k
0
votes
1
answer
49
views
Extract a strongly typed expression from a function expression body
I'm trying to write a "relaxed" comparison method which operates on Expressions and is used in Entity Framework. It consists of a chain of Replace() calls and ToLower() to perform an inexact ...
- 1,022
3
votes
2
answers
87
views
Why isn't my supplied predicate being matched when using Moq?
Given a simple type I'm testing, say
interface IMyRepo
{
MyObj GetBy(Expression<Func<MyObj, bool> predicate);
}
so the standard mock setup works just fine:
_repoMock.Setup(x => x.GetBy(...
- 1,330
0
votes
1
answer
78
views
How to find entity types in IQueryExpressionInterceptor?
How can I find all the entity types referenced by the Expression passed to IQueryExpressionInterceptor.QueryCompilationStarting? Where in the expression tree should I look for them?
I've tried a ...
- 10.3k
2
votes
1
answer
76
views
Pattern matching with Expression<Func<T, bool>>
Consider the following code:
internal static class Program
{
private static void Main()
{
object value = "Hello";
Console.WriteLine(value.Test(o => o is string));
...
- 42.5k
2
votes
2
answers
87
views
Dynamically created event handler that writes ito a `ref` parameter
I want to subscribe to any event existing on a given object, where I don't know the type in advance. I'm generatig event handler at run-time using System.Linq.Expressions.Expression.
The code I have (...
- 500
0
votes
0
answers
32
views
The type arguments for method cannot be inferred from the usage, but explicitly defining removes benefits of intended usage [duplicate]
I'm having some trouble understanding why the type arguments can't be inferred from the usage below.
While the types can clearly be inferred in Build, I'm struggling to understand why (I'm assuming) ...
- 117
1
vote
1
answer
103
views
Possible to use LINQ Expression with Delegate Signature to obtain parameters?
Is it possible to obtain ParameterInfo and argument values for a delegate invocation which is inside a (compiler-generated) LambdaExpression?
For example I have defined a delegate:
public class A
{
...
- 10.2k
2
votes
2
answers
160
views
How can I reuse the logic in a .Include.Where() call while working with Entity Framework Core in .NET?
I am writing a database query using LINQ in .NET and I want to be able to not duplicate the code I put in my Where method calls.
I want to return Blogs that have fresh Comments, and want to filter ...
- 383
0
votes
0
answers
178
views
Microsoft's rule engine throws an exception if the input lacks the specified property
I am using Microsoft's rule engines. The issue arises when the expression references a property that does not exist in the input object, causing the RuleExpressionParser to throw an exception.
private ...
- 34.4k
0
votes
0
answers
52
views
How to Replace a MethodCall With a Lambda in Visit()
I have code that will replace an annotated property in a LINQ query with a predefined lambda. Here's an example of such a property, followed by the Visitor code that does the replacement:
public ...
- 1,421
0
votes
0
answers
23
views
Strange ArgumentException in Expression Tree Query Statement
Note: the answer can be in either VB.NET or C#. I have no preference for this Q&A.
I'm trying to distill this rather cumbersome line:
Dim oSession As Session
oSession = Await Me.DbContext....
- 6,437
2
votes
1
answer
89
views
Compile deserialized Expression using Serialize.Linq
I'm not able to find the way how to compile the deserialized Expression using Serialize.Linq. The accepted answer in "Compile Expression at runtime Using Serialize.Linq" doesn't work (part 2 ...
- 4,774
1
vote
1
answer
55
views
What is wrong with this Reflection.Emit for value conversion delegates?
Sorry for this long question but I feel I have to provide a bit more background as my issue is very specific.
Bigger picture
I am developing on a Unity tool to be used specifically for Embedded Linux ...
- 91.4k
0
votes
1
answer
51
views
Can I reuse one Expression object for multiple lambdas building?
I want to reuse Expression instances for another Expression building like in the code below. Is it safe? Are there any pitfalls with it?
using System.Linq.Expressions;
class Program
{
static void ...
