IDistributedCache GetOrCreateAsync extension method.

IDistributedCache.GetOrCreateAsync.cs

public static class DistributedCacheExtensions
{
    public static async Task<T?> GetOrCreateAsync<T>(
        this IDistributedCache cache, 
        string key, 
        Func<DistributedCacheEntryOptions, Task<T>> factory,  
        CancellationToken cancellationToken = default)
    {
        var value = await cache.GetStringAsync(key, cancellationToken);
        if(string.IsNullOrWhiteSpace(value))
        {
            var options = new DistributedCacheEntryOptions();
            var result = await factory(options);
            await cache.SetStringAsync(key, JsonSerializer.Serialize(result), options, cancellationToken);
            return result;
        }
        else
        {
            return JsonSerializer.Deserialize<T>(value);
        }
    }
}