[jira] Commented: (IBATISNET-221) InvalidCastException while getting object out of the cache

["Douglas M. Smith (JIRA)" <ib...@incubator.apache.org>]

    [ https://issues.apache.org/jira/browse/IBATISNET-221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12504480 ] 

Douglas M. Smith commented on IBATISNET-221:
--------------------------------------------

Here is a temporary work around: 

//This method seems to return a strange iBatis error when CACHE is enabled and the result is NULL.
return dataMapper.Instance().QueryForObject<MyObject>("MyQueryName", MyParams); 

//This method seems to work with cache enabled.
return (MyObject)dataMapper.Instance().QueryForObject("MyQueryName", MyParams);


> InvalidCastException while getting object out of the cache
> ----------------------------------------------------------
>
>                 Key: IBATISNET-221
>                 URL: https://issues.apache.org/jira/browse/IBATISNET-221
>             Project: iBatis for .NET
>          Issue Type: Bug
>          Components: DataMapper
>    Affects Versions: DataMapper 1.6.1
>         Environment: IBatis.net SVN, revision 527493, .Net 2.0
>            Reporter: Rogelio J. Baucells
>            Priority: Critical
>
> There is a problem in the implementation of CachingStatement::ExecuteQueryForObject for .Net2.0. The following scenario triggers the InvalidCastException:
> - Create a <ResultMap>, <procedure>, <parameterMap> and <cacheModel> for a select statement.
> - Invoke the statement with parameters that does not return any results
> - Invoke the same statement again
> The first invocation will store a NULL_OBJECT in the cache for this key (CacheModel::this[CacheKey key]), the second statement will retrieve the NULL_OBJECT from the cache and will cause the InvalidCastException at:
> obj = (T)this.Statement.CacheModel[cacheKey];
> Also the next statement will never be TRUE since obj is of type T:
> if ((object)obj == CacheModel.NULL_OBJECT)
> The solution for this problem would be declaring obj as object and casting to T at the time of returning from the method, something like:
> object obj = null;
> ...
> return (T)obj;

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