SqlCacheDependency
对象的HasChanged
值最初在命令执行时返回false,但几乎立即在从数据库返回后更改为true。有时候,在项目插入缓存之前就会发生这种情况,导致缓存立即丢弃它;有时候是在插入之后,我可以获取一个枚举器,看到缓存中的键,但在我循环到该项之前,它已被删除。SPROC:
ALTER PROCEDURE [dbo].[ntz_dal_ER_X_Note_SelectAllWER_ID]
@ER_ID int
AS
BEGIN
SELECT
ER_X_Note_ID,
ER_ID,
Note_ID
FROM dbo.ER_X_Note e
WHERE
ER_ID = @ER_ID
END
数据库是MS SQL Server 2008,代理服务已启用,并且有些输出会缓存并保持缓存状态。例如,这个可以正常工作:
ALTER PROC [dbo].[ntz_dal_GetCacheControllerByEntityName] (
@Name varchar(50)
) AS
BEGIN
SELECT
CacheController_ID,
EntityName,
CacheEnabled,
Expiration
From dbo.CacheController cc
WHERE EntityName = @Name
END
调用失败的存储过程的代码如下:
DataSet toReturn;
Hashtable paramHash = new Hashtable();
paramHash.Add("ER_ID", _eR_ID.IsNull ? null : _eR_ID.Value.ToString());
string cacheName = BuildCacheString("ntz_dal_ER_X_Note_SelectAllWER_ID", paramHash);
toReturn = (DataSet)GetFromCache(cacheName);
if (toReturn == null)
{
// Set up parameters (1 input and 0 output)
SqlParameter[] arParms = {
new SqlParameter("@ER_ID", _eR_ID),
};
SqlCacheDependency scd;
// Execute query.
toReturn = _dbTransaction != null
? _dbConnection.ExecuteDataset(_dbTransaction, "dbo.[ntz_dal_ER_X_Note_SelectAllWER_ID]", out scd, arParms)
: _dbConnection.ExecuteDataset("dbo.[ntz_dal_ER_X_Note_SelectAllWER_ID]", out scd, arParms);
AddToCache(cacheName, toReturn, scd);
}
return toReturn;
代码能够运行
const string sprocName = "ntz_dal_GetCacheControllerByEntityName";
string cacheControlPrefix = "CacheController_" + CachePrefix;
CacheControl controller = (CacheControl)_cache[cacheControlPrefix];
if (controller == null)
{
try
{
SqlParameter[] arParms = {
new SqlParameter("@Name", CachePrefix),
};
SqlCacheDependency sqlCacheDependency;
// Execute query.
DataSet result = _dbTransaction != null
? _dbConnection.ExecuteDataset(_dbTransaction, sprocName, out sqlCacheDependency, arParms)
: _dbConnection.ExecuteDataset(sprocName, out sqlCacheDependency, arParms);
controller = result.Tables[0].Rows.Count == 0
? new CacheControl(false)
: new CacheControl(result.Tables[0].Rows[0]);
_cache.Insert(cacheControlPrefix, controller, sqlCacheDependency);
}
catch (Exception ex)
{
// if sproc retreival fails cache the result of false so we don't keep trying
// this is the only case where it can be added with no expiration date
controller = new CacheControl(false);
// direct cache insert, no dependency, no expiration, never try again for this entity
if (HttpContext.Current != null && UseCaching && _cache != null) _cache.Insert(cacheControlPrefix, controller);
}
}
return controller;
AddToCache
方法是重载的,并且其中有更多的测试;在工作方法中直接使用_cache.Insert
是为了绕过其他测试。工作代码有助于确定是否应该进行数据库缓存。您可以看到,当“不工作”的数据最初被检索时,一切都正常:
![enter image description here](https://istack.dev59.com/k9K1s.webp)
![enter image description here](https://istack.dev59.com/dPmJM.webp)
new SqlParameter("@ER_ID", _eR_ID)
上。这将整个 _eR_ID 对象传递给参数,我不确定它如何将其转换为 Sql 的值(我怀疑它调用对象的 ToString() 方法)。在代码的早期,您使用了 _eR_ID.Value,因此我认为您需要进行的最小更改是new SqlParameter("@ER_ID", _eR_ID.Value)
。 - competent_tech