InvalidOperationException when accessing property from dynamically generated class-type in Blazor WASM .NET 8

[StefH]

Description

When a type is dynamically created using System.Reflection.Emit code, accessing a field or property throws InvalidOperationException.

Reproduction Steps

Create a .NET 8 WASM Blazor project.

Include System.Linq.Dynamic.Core

Add this code to the default Counter.cs code which creates dynamically a type and a instance of that type:

var props = new DynamicProperty[] { new("Name", typeof(string)), new("Birthday", typeof(DateTime)) };
var type = DynamicClassFactory.CreateType(props);
var dynamicClass = (DynamicClass)Activator.CreateInstance(type, false)!;
dynamicClass.SetDynamicPropertyValue("Name", "Albert");
dynamicClass.SetDynamicPropertyValue("Birthday", new DateTime(1879, 3, 14));

Now when casting this to dynamic and accessing the "Name" property throws exception:

Console.WriteLine(((dynamic)dynamicClass).Name);

Not that accessing the properties using reflection works fine:

var nameReflection = dynamicClass.GetType().GetProperty("Name")!.GetValue(dynamicClass);
Console.WriteLine("Reflection = " + nameReflection);

See this issue + fully working example project to show this error:
zzzprojects/System.Linq.Dynamic.Core#836

Expected behavior

The "Name" property should be accessible.

Actual behavior

crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
      Unhandled exception rendering component: Operation is not valid due to the current state of the object.
System.InvalidOperationException: Operation is not valid due to the current state of the object.
   at System.Reflection.Emit.RuntimeGenericTypeParameterBuilder.GetGenericParameterConstraints()
   at Microsoft.CSharp.RuntimeBinder.SymbolTable.AddAggregateToSymbolTable(NamespaceOrAggregateSymbol parent, Type type)
   at Microsoft.CSharp.RuntimeBinder.SymbolTable.LoadSymbolsFromType(Type type)
   at Microsoft.CSharp.RuntimeBinder.SymbolTable.GetCTypeFromType(Type type)
   at Microsoft.CSharp.RuntimeBinder.RuntimeBinder.GetArgumentType(ICSharpBinder p, CSharpArgumentInfo argInfo, Expression param, DynamicMetaObject arg, Int32 index)
   at Microsoft.CSharp.RuntimeBinder.RuntimeBinder.CreateArgumentArray(ICSharpBinder payload, Expression[] parameters, DynamicMetaObject[] args)
   at Microsoft.CSharp.RuntimeBinder.RuntimeBinder.BindCore(ICSharpBinder payload, Expression[] parameters, DynamicMetaObject[] args, DynamicMetaObject& deferredBinding)
   at Microsoft.CSharp.RuntimeBinder.RuntimeBinder.Bind(ICSharpBinder payload, Expression[] parameters, DynamicMetaObject[] args, DynamicMetaObject& deferredBinding)
   at Microsoft.CSharp.RuntimeBinder.BinderHelper.Bind(ICSharpBinder action, RuntimeBinder binder, DynamicMetaObject[] args, IEnumerable`1 arginfos, DynamicMetaObject onBindingError)
   at Microsoft.CSharp.RuntimeBinder.CSharpGetMemberBinder.FallbackGetMember(DynamicMetaObject target, DynamicMetaObject errorSuggestion)
   at System.Dynamic.GetMemberBinder.FallbackGetMember(DynamicMetaObject target)
   at System.Dynamic.DynamicMetaObject.BindGetMember(GetMemberBinder binder)
   at System.Dynamic.GetMemberBinder.Bind(DynamicMetaObject target, DynamicMetaObject[] args)
   at System.Dynamic.DynamicMetaObjectBinder.Bind(Object[] args, ReadOnlyCollection`1 parameters, LabelTarget returnLabel)
   at System.Runtime.CompilerServices.CallSiteBinder.BindCore[Func`3](CallSite`1 site, Object[] args)
   at System.Dynamic.UpdateDelegates.UpdateAndExecute1[Object,Object](CallSite site, Object arg0)
   at WasmDynamicLinq.Pages.Home.OnInitialized() in C:\Dev\GitHub\System.Linq.Dynamic.Core\src-blazor\WasmDynamicLinq\Pages\Home.razor.cs:line 142
   at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()
Dt @ blazor.webassembly.js:1
(anonymous) @ invoke-js.ts:176
Tl @ invoke-js.ts:276
$func349 @ 00b21cf6:0x1fafb
$func245 @ 00b21cf6:0x1bf9f
$func238 @ 00b21cf6:0xf16c
$func272 @ 00b21cf6:0x1d1bd
$func3185 @ 00b21cf6:0xe8756
$func2505 @ 00b21cf6:0xbe4ac
$func2511 @ 00b21cf6:0xbecd0
$func2535 @ 00b21cf6:0xc1327
$mono_wasm_invoke_method_bound @ 00b21cf6:0xa4fa
Module._mono_wasm_invoke_method_bound @ dotnet.native.8.0.7.37dkch2d2y.js:8
kr @ invoke-cs.ts:273
l.javaScriptExports.complete_task @ managed-exports.ts:142
(anonymous) @ marshal-to-cs.ts:335
Promise.then
mo @ marshal-to-cs.ts:329
(anonymous) @ marshal-to-cs.ts:83
(anonymous) @ invoke-js.ts:177
Tl @ invoke-js.ts:276
$func349 @ 00b21cf6:0x1fafb
$func245 @ 00b21cf6:0x1bf9f
$func238 @ 00b21cf6:0xf16c
$func272 @ 00b21cf6:0x1d1bd
$func3185 @ 00b21cf6:0xe8756
$func2505 @ 00b21cf6:0xbe4ac
$func2504 @ 00b21cf6:0xbe43c
$func1874 @ 00b21cf6:0x9a502
$func349 @ 00b21cf6:0x1fb7f
$func245 @ 00b21cf6:0x1bf9f
$func238 @ 00b21cf6:0xf16c
$func272 @ 00b21cf6:0x1d1bd
$func3185 @ 00b21cf6:0xe8756
$func2505 @ 00b21cf6:0xbe4ac
$func2511 @ 00b21cf6:0xbecd0
$func2535 @ 00b21cf6:0xc1327
$mono_wasm_invoke_method_bound @ 00b21cf6:0xa4fa
Module._mono_wasm_invoke_method_bound @ dotnet.native.8.0.7.37dkch2d2y.js:8
kr @ invoke-cs.ts:273
l.javaScriptExports.call_entry_point @ managed-exports.ts:60
Oc @ run.ts:44
callEntryPoint @ blazor.webassembly.js:1
mn @ blazor.webassembly.js:1
await in mn
fn @ blazor.webassembly.js:1
An @ blazor.webassembly.js:1
(anonymous) @ blazor.webassembly.js:1
(anonymous) @ blazor.webassembly.js:1

Regression?

No response

Known Workarounds

No response

Configuration

.NET 8

Blazor WAM

<Project Sdk="Microsoft.NET.Sdk.BlazorWebAssembly">

Other information

No response

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[StefH]

@cston
I was able to trim down the issue to the part when I make the type a generic type:

This code works:

// Define a dynamic assembly and module
AssemblyName assemblyName = new AssemblyName("DynamicAssembly");
AssemblyBuilder assemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.RunAndCollect);
ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule("DynamicModule");

// Define a public class named "DynamicType"
TypeBuilder typeBuilder = moduleBuilder.DefineType("DynamicType", TypeAttributes.Public);

// Define a public field of type string named "MyField"
typeBuilder.DefineField("MyField", typeof(string), FieldAttributes.Public);

// Create the type
Type dynamicType = typeBuilder.CreateType();

// Create an instance of the dynamic type
dynamic dynamicObject = Activator.CreateInstance(dynamicType)!;

// Set the value of the field using reflection
FieldInfo fieldInfo = dynamicType.GetField("MyField", BindingFlags.Public | BindingFlags.Instance)!;
fieldInfo.SetValue(dynamicObject, "Hello, World!");

// Output the value
Console.WriteLine("Test Field Value: " + (string)fieldInfo.GetValue(dynamicObject));
Console.WriteLine("Test Field Value Dynamic: " + dynamicObject.MyField);

This code does not work

// Define a dynamic assembly and module
AssemblyName assemblyName = new AssemblyName("DynamicAssembly");
AssemblyBuilder assemblyBuilder = AssemblyBuilder.DefineDynamicAssembly(assemblyName, AssemblyBuilderAccess.RunAndCollect);
ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule("DynamicModule");

// Define a public class named "DynamicType"
TypeBuilder typeBuilder = moduleBuilder.DefineType("DynamicType", TypeAttributes.Public);

// Define a public field of type string named "MyField"
typeBuilder.DefineField("MyField", typeof(string), FieldAttributes.Public);

// ▶️ Define Generic Parameter
typeBuilder.DefineGenericParameters("T0");

// Create the type
Type dynamicType = typeBuilder.CreateType();

// ▶️ Make it generic
dynamicType = dynamicType.MakeGenericType(typeof(string));

// Create an instance of the dynamic type
dynamic dynamicObject = Activator.CreateInstance(dynamicType)!;

// Set the value of the field using reflection
FieldInfo fieldInfo = dynamicType.GetField("MyField", BindingFlags.Public | BindingFlags.Instance)!;
fieldInfo.SetValue(dynamicObject, "Hello, World!"); // ▶️ this throws exception

// Output the value
Console.WriteLine("Test Field Value: " + (string)fieldInfo.GetValue(dynamicObject));
Console.WriteLine("Test Field Value Dynamic: " + dynamicObject.MyField);

Can you explain this?