How to create memory cache with async generator

Question

I tried to create cache with async getter method which reads data from databae using EF Core in ASP.NET 5 Core MVC application:

using Microsoft.Extensions.Caching.Memory;
using System;
using System.Threading.Tasks;

    public sealed class CacheManager
    {
        readonly IMemoryCache memoryCache;
        public CacheManager(IMemoryCache memoryCache)
        { 
            this.memoryCache = memoryCache;
        }

        public async Task<T> GetAsync<T>(string key, Task<Func<T>> generatorasync)
        {
            var cacheEntry = await
                  memoryCache.GetOrCreateAsync<T>(key, async entry =>
                  {
                      entry.SlidingExpiration = TimeSpan.FromSeconds(15 * 60);
                      return await generatorasync();
                  });
            return cacheEntry;
        }
    }

Line

              return await generatorasync();

throws syntax error

CS0149: Method name expected

Hoe to fix it ? Which is best practice to create such cache ?

Andrus.

Answer 1

Hi @AndRus ,

CS0149: Method name expected

To solve this issue, you can try to change the parameter type from Task<Func<T>> to Func<Task<T>>.

After modified, the result as below:

public sealed class CacheManager  
{  
    private readonly IMemoryCache memoryCache;  
    public CacheManager(IMemoryCache memoryCache)  
    {  
        this.memoryCache = memoryCache;  
    }  

    public async Task<T> GetAsync<T>(string key, Func<Task<T>> generatorasync)  
    {  
        var cacheEntry = await  
              memoryCache.GetOrCreateAsync<T>(key, async entry =>  
              {  
                  entry.SlidingExpiration = TimeSpan.FromSeconds(15 * 60);   
                  return await generatorasync();  
              });  
        return cacheEntry;  
    }  
}  

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