When using Microsoft.SemanticKernel, it's recommended to maintain long-lived kernel instances rather than re-creating them for each consumer or request. This avoids the overhead of reconfiguring connectors or plugins every time you need to perform a semantic operation. The SemanticKernelCache provides a thread-safe singleton cache per key via dependency injection. Kernel instances are created lazily using customizable options and disposed on application shutdown (or manually if needed).
Installation
Install the package via the .NET CLI:
dotnet add package Soenneker.SemanticKernel.Cache
Usage
1. Register the Cache in Dependency Injection
In your Program.cs (or equivalent startup file), register the cache with the DI container:
using Soenneker.SemanticKernel.Cache;
public static async Task Main(string[] args)
{
var builder = WebApplication.CreateBuilder(args);
// Register SemanticKernelCache as a singleton service.
builder.Services.AddSemanticKernelCacheAsSingleton();
// Other configuration...
}
2. Inject and Retrieve a Kernel Instance
Inject ISemanticKernelCache into your classes and retrieve a Microsoft.SemanticKernel.Kernel instance by providing the required options.
using System.Threading;
using System.Threading.Tasks;
using Microsoft.SemanticKernel;
using Microsoft.SemanticKernel.Chat;
using Soenneker.SemanticKernel.Cache;
public class TestClass
{
private readonly ISemanticKernelCache _semanticKernelCache;
private readonly SemanticKernelOptions _options;
public TestClass(ISemanticKernelCache semanticKernelCache)
{
_semanticKernelCache = semanticKernelCache;
// Create the options object once. Replace these with your actual values.
var options = new SemanticKernelOptions
{
ModelId = "deepseek-r1:32b",
Endpoint = "http://localhost:11434",
KernelFactory = (opts, ct) =>
{
IKernelBuilder builder = Kernel.CreateBuilder().AddOllamaChatCompletion(opts.ModelId, new Uri(opts.Endpoint));
return ValueTask.FromResult(builder);
}
};
}
public async async ValueTask<string> GetKernelResponse(string input, CancellationToken cancellationToken = default)
{
// Retrieve (or create) the kernel instance using a key (here, nameof(TestClass)).
Kernel kernel = await _semanticKernelCache.Get(nameof(TestClass), _options, cancellationToken);
// Retrieve the chat completion service from the kernel.
var chatCompletionService = kernel.GetRequiredService<IChatCompletionService>();
// Create a chat history and add the user's message.
var history = new ChatHistory();
history.AddUserMessage(input);
// Request a chat completion using the chat service.
var chatResult = await chatCompletionService.GetChatMessageContentAsync(history, kernel: kernel);
// Return the chat result (or process it further as needed).
return chatResult.ToString();
}
}
Extending for Different Connectors/Plugins
The SemanticKernelOptions class includes an optional KernelFactory delegate. This allows you to override the default behavior (which uses the Azure Text Completion service) and create the kernel using a different connector or plugin. For example:
Soenneker.SemanticKernel.Cache