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[Blazor] Clarify trimming behavior for custom types #36094

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Sep 18, 2025
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[Blazor] Clarify trimming behavior for custom types #36094

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[Blazor] Clarify trimming behavior for custom types
hakenr Sep 10, 2025
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guardrex Sep 18, 2025
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10 changes: 5 additions & 5 deletions aspnetcore/blazor/host-and-deploy/configure-trimmer.md
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Expand Up @@ -83,20 +83,20 @@ Consider the following example that performs JSON deserialization into a <xref:S

The preceding component executes normally when the app is run locally and produces the following rendered list:

> • 1:T1, 1:T2
> • 1:T1, 1:T2
> • 2:T2, 2:T2

When the app is published, <xref:System.Tuple%602> is trimmed from the app, even in spite of setting the `<PublishTrimmed>` property to `false` in the project file. Accessing the component throws the following exception:

> :::no-loc text="crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]":::
> :::no-loc text="Unhandled exception rendering component: ConstructorContainsNullParameterNames, System.Tuple`2[System.String,System.String]":::
> :::no-loc text="crit: Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]":::
> :::no-loc text="Unhandled exception rendering component: ConstructorContainsNullParameterNames, System.Tuple`2[System.String,System.String]":::
> :::no-loc text="System.NotSupportedException: ConstructorContainsNullParameterNames, System.Tuple`2[System.String,System.String]":::

To address lost types, consider adopting one of the following approaches.

### Custom types

Custom types aren't trimmed by Blazor when an app is published, so we recommend using custom types for JS interop, JSON serialization/deserialization, and other operations that rely on reflection.
Custom types aren't trimmed by Blazor when an app is published (unless explicitly opted in), so we recommend using custom types for JS interop, JSON serialization/deserialization, and other operations that rely on reflection.

The following modifications create a `StringTuple` type for use by the component.

Expand All @@ -123,7 +123,7 @@ The component is modified to use the `StringTuple` type:
+ items = JsonSerializer.Deserialize<List<StringTuple>>(data, options)!;
```

Because custom types are never trimmed by Blazor when an app is published, the component works as designed after the app is published.
Because custom types aren't trimmed by Blazor when an app is published (unless explicitly opted in), the component works as designed after the app is published.

:::moniker range=">= aspnetcore-10.0"

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