docs: modernize grain programming guidance - #10334

docs/site/src/content/docs/grains/grain-placement-filtering.md:58

• This attribute example uses a collection expression (["rack", "zone"]) as an attribute argument, which is not valid in C# attribute syntax. Use an array creation expression instead so the sample compiles.

[PreferredMatchSiloMetadataPlacementFilter(
    ["rack", "zone"],
    minCandidates: 2)]

docs/site/src/content/docs/grains/grain-placement-filtering.md:77

• This attribute example uses a collection expression (["tier"]) as an attribute argument, which is not valid in C# attribute syntax. Use an array creation expression instead so the sample compiles.

[RequiredMatchSiloMetadataPlacementFilter(
    ["tier"],
    order: 0)]

docs/site/src/content/docs/grains/grain-placement-filtering.md:81

• This attribute example uses a collection expression (["rack", "zone"]) as an attribute argument, which is not valid in C# attribute syntax. Use an array creation expression instead so the sample compiles.

[PreferredMatchSiloMetadataPlacementFilter(
    ["rack", "zone"],
    minCandidates: 2,
    order: 10)]

docs/site/src/content/docs/grains/grain-references.md:48

• The marker-interface example uses public interface ... : ICounterGrain;, which is not valid C#. Interfaces require a body, even when empty, so readers copying this snippet will get a compile error.

public interface IUpCounterGrain : ICounterGrain;

public interface IDownCounterGrain : ICounterGrain;

docs/site/src/content/docs/grains/grain-placement-filtering.md:39

• This attribute example uses a collection expression (["zone", "tier"]) as an attribute argument, which is not valid in C# attribute syntax. Use an array creation expression instead so the sample compiles.

This issue also appears in the following locations of the same file:

• line 56
• line 75
• line 78

[RequiredMatchSiloMetadataPlacementFilter(
    ["zone", "tier"])]

docs/site/src/content/docs/grains/grain-placement.md:16

• The description of resource-optimized placement omits the MaxAvailableMemory signal, but the implementation and options include it (ResourceOptimizedPlacementOptions.MaxAvailableMemoryWeight) and it contributes to the score. Consider mentioning it and including it in the configuration snippet to avoid misleading readers.

<xref:Orleans.Runtime.ResourceOptimizedPlacement> is the default placement strategy. It uses sampled silo runtime statistics and a power-of-k-choices algorithm to balance new activations while avoiding overloaded silos. It considers CPU, memory, available memory, activation count, and a preference for the local silo.

Configure its weights through <xref:Orleans.Configuration.ResourceOptimizedPlacementOptions>: