I've got myself very confused, and I wonder if you guys can help a
little bit.
In my data-layer, I'm trying to implement some caching for a long (well
2-3 seconds) running database operation. I know when the results would
have changed, so when to re-run the stored proc. The stored proc takes
some parameters which varies the output. So I need to have a hashtable
of results. It needs to be thread-safe.
Here's the non-cached version. GetListLong would actually execute the
stored proc.
DataTable GetList(int a, int b, int c) {
return GetListLong(a, b, c);
}
Here's a version which looks good:
Hashtable ht = new Hashtable();
public DataTable GetList(int a, int b, int c)
{
lock (ht.SyncRoot)
{
HashKey key = new HashKey(a,b,c);
DataTable dt = (DataTable)ht[key];
if (Expired(dt) == true) {
dt = GetListLong(a,b,c);
ht[key] = dt;
}
if (dt == null)
{
dt = GetListLong(a, b, c);
ht.Add(key, dt);
}
}
return dt;
}
But, I can see this would not be particularly fast, since only a single
reader would be allowed into the code loop.
What I really want to do is allow multiple users to read, AND multiple
calls to GetListLong - as long as the parameters are different (if there
is one already executing, wait for that to finish and get the results) -
but, of course, add to the hashtable with thread safety.
I'm sure there must be a really elegant way to do this. Any hints?
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