When running in Blazor WASM, constructor is being skipped and instance is returned from ordinary property

[FelipeCostaGualberto]

Category

• Bug

Describe the bug

I'm having a very strange error when referring PnPCore from a Blazor WASM Web App, but in Blazor Server works as expected.

The error happens when PnpCore builds a request batch. Refer here.

I rewrote it just adding a WriteLine before:

Console.WriteLine("batchRequestId being passed as parameter: " + batchRequestId.ToString()); // prints valid GUID such as 59174352-e729-4787-923b-b117235cf925
return new BatchSingleResult<TModel>(batch, batchRequestId, testGuid);

Then the code flows to this constructor, but:

public BatchSingleResult(Batch batch, Guid batchRequestId, Guid testGuid) : base(batch, batchRequestId, testGuid)
{
    // Blazor Server hits this constructor, but Blazor WASM doesn't!!!
}

The weird part is that Blazor WASM hits this statement instead of the constructor above:

public static IBatchSingleResult<T> None { get; } = new BatchSingleResult<T>(null, Guid.Empty);

And then, the code - both in Blazor WASM and Server - flows to the parent constructor:

public BatchResult(Batch batch, Guid batchRequestId, Guid testGuid)
{
    // In Blazor Server, the GUID has the expected value (such as 59174352-e729-4787-923b-b117235cf925)
    // In Blazor WASM, the GUID has the a "default" value: 00000000-0000-0000-0000-000000000000

Why didn’t WASM call the constructor but did call an ordinary static property? Is this a compiler detail related to how C# runs in the browser? Or is it related to trimming or heavy reflection in the PnP library that I haven’t checked yet?

The only place in the library that BatchSingleResult<TModel>.None is used is in the code below (also in BaseBatchRetrieveAsync), but this condition never hits in my application!

if (api.Cancelled)
{
    ApiCancellationMessage(api);
    return BatchSingleResult<TModel>.None;
}

Solution (Edit)

The fix confirms the weird behavior.

1 - delete this line:

public static IBatchSingleResult<T> None { get; } = new BatchSingleResult<T>(null, Guid.Empty);

2 - The code won't compile because of this:

if (api.Cancelled)
{
    ApiCancellationMessage(api);
    return BatchSingleResult<TModel>.None;
}

Just change it for what we just deleted:

if (api.Cancelled)
{
    ApiCancellationMessage(api);
    return new BatchSingleResult<TModel>(null, Guid.Empty);
}

And now it works.

Environment details (development & target environment)

• SDK version: current (1.14.0)
• OS: Windows 11
• SDK used in: Blazor WebAssembly
• Framework: .NET Core v9.0 (9.0.102)
• Browser(s): Chrome v133.0.6943.126 64 bits
• Tooling: Visual Studio 2022