Question

我正在尝试使用AppFabric来固定从SQL数据库中检索图像。我创建了我的提供程序文件并将其加载到我的缓存中。但是，我现在正在努力。

如何使用我的提供程序文件从缓存中调用get函数，或者在检索数据时是否需要使用我的提供程序文件？

当我调用.Get（key.Key）时，是否需要查看来自我的数据库的数据？

来自提供商的My Read方法如下，这是正确的吗？

public override DataCacheItem Read(DataCacheItemKey key)
    {       
        try
        {
            Object retrievedValue = null;
            DataCacheItem cacheItem;

            retrievedValue = *Running SQL Query Retrieving Image from DB*;//Is that a correct approach? 

            if (retrievedValue == null)
                cacheItem = null;
            else
                cacheItem = DataCacheItemFactory.GetCacheItem(key, cacheName, retrievedValue, null);
            return cacheItem;
        }
        catch
        {
            return null;
        }
    }

Answer 1

Example:>

using Microsoft.ApplicationServer.Caching;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlClient;

namespace SampleProvider
{
  public class Provider : DataCacheStoreProvider
  {
    private readonly String dataCacheName;
    private readonly Dictionary<string, string> config;

    public Provider(string cacheName, Dictionary<string, string> config)
    {
      this.dataCacheName = cacheName; //Store the cache name for future use
      this.config = config;
    }

    public override DataCacheItem Read(DataCacheItemKey key)
    {
      Object retrievedValue = null;
      DataCacheItem cacheItem;

      retrievedValue = ReadFromDatabase(key.Key); //Your implemented method that searches in the backend store based

      if (retrievedValue == null)
        cacheItem = null;
      else
        cacheItem = DataCacheItemFactory.GetCacheItem(key, dataCacheName, retrievedValue, null);
      return cacheItem;
    }
    public override void Read(System.Collections.ObjectModel.ReadOnlyCollection<DataCacheItemKey> keys, IDictionary<DataCacheItemKey, DataCacheItem> items)
    {
      foreach (var key in keys)
      {
        items[key] = Read(key);
      }
    }

    public override void Delete(System.Collections.ObjectModel.Collection<DataCacheItemKey> keys) { }

    public override void Delete(DataCacheItemKey key) { }

    protected override void Dispose(bool disposing) { }

    public override void Write(IDictionary<DataCacheItemKey, DataCacheItem> items) { }

    public override void Write(DataCacheItem item) { }


    private string ReadFromDatabase(string key)
    {
      string value = string.Empty;
      object retrievedValue = null;
      using (SqlConnection connection = new SqlConnection(config["DBConnection"]))
      {
        SqlCommand cmd = new SqlCommand();
        cmd.CommandText = string.Format("select Value from KeyValueStore where [Key] = '{0}'", key);
        cmd.Connection = connection;
        connection.Open();
        retrievedValue = cmd.ExecuteScalar();
        if (retrievedValue != null)
        {
          value = retrievedValue.ToString();
        }
      }

      return value;
    }
  }
}

AppFabric-ReadThrough实现如何获取数据？

1 个答案: