Implementing ICustomMemberProvider without referencing Linqpad.

sgmoore · May 12

I'm wondering if your advice from this really, really old stackoverflow question is still relevant.

In particular this bit :

Note that if the test class is defined in another assembly, you don't need to reference LINQPad in order to implement ICustomMemberProvider. You can just paste in the following definition into your project and LINQPad will pick it up:

namespace LINQPad
{
   public interface ICustomMemberProvider
   {
      IEnumerable<string> GetNames ();
      IEnumerable<Type> GetTypes ();
      IEnumerable<object> GetValues ();
   }
}

I'm trying to do this and it is not working and I am getting errors in the log file

9.8.11 (X64) 2026-05-12T16:27:56.7486577+01:00 CustomMemberProvider
InvalidOperationException - Sequence contains no matching element

Source=System.Linq

 -System.Linq.ThrowHelper Void ThrowNoMatchException() offset: 0xA
 -System.Linq.Enumerable TSource First[TSource](System.Collections.Generic.IEnumerable`1[TSource], System.Func`2[TSource,System.Boolean]) offset: 0x0
 -LINQPad.ObjectGraph.CustomMemberProviderNode Void .ctor(LINQPad.ObjectGraph.ObjectNode, System.Object, Boolean, LINQPad.ObjectGraph.GraphOptions, Boolean, System.Object) offset: 0xCC
 -LINQPad.ObjectGraph.CustomMemberProviderNode LINQPad.ObjectGraph.ObjectNode CreateFromCustomMemberProvider(LINQPad.ObjectGraph.ObjectNode, System.Object, Boolean, LINQPad.ObjectGraph.GraphOptions, Boolean, System.Object) offset: 0x1
 -LINQPad.ObjectGraph.ObjectNode LINQPad.ObjectGraph.ObjectNode CreateInternal(LINQPad.ObjectGraph.ObjectNode, System.Object, System.Type, Boolean, LINQPad.ObjectGraph.GraphOptions, System.Object, Boolean ByRef) offset: 0xA61

sgmoore · May 13

The solution or workaround appears to be - not to call UseLazyLoadingProxies which is acceptable in this case.

JoeAlbahari · May 13

All three methods need to return at least one element, and each method needs to return the same number of elements. Then it should work.

sgmoore · May 13

This is a test class

using LINQPad;
using System;
using System.Collections.Generic;

public partial class Foo  
{  
    public string DATE { get; set; }
}

public partial class Foo : ICustomMemberProvider
{
    public string FirstName , LastName , Junk ;

    IEnumerable<string> ICustomMemberProvider.GetNames()
        => new string[] { "FirstName", "LastName" };

    IEnumerable<Type> ICustomMemberProvider.GetTypes()
        => new Type[] { typeof(string), typeof(string) };

    IEnumerable<object> ICustomMemberProvider.GetValues()
        => new object[] { FirstName, LastName };
}

It appears work when I create a new Foo object, but not when I am doing Linq Queries

void Main()
{
    Show(new Foo());
    Show(Foo.First());
}

public void Show<T>(T input)
{
    var type = input.GetType();
    var interfaces = type.GetInterfaces().Select(a => a.FullName);
    (new { input, type, interfaces }).Dump(type.Name);
}

produces

The linq results are FooProxy objects which appear to implement ICustomMemberProvider (although I can find a way to decompile this as ILSpy says - Cannot find 'T:Castle.Proxies.FooProxy' in command line specified assemblies).

Implementing ICustomMemberProvider without referencing Linqpad.

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