Fill Dropdown in asp dotnet from Caching - asp.net

Question

I have a dropdown in asp.net which fills with Agent list. now agent list is 30,000. So I want to keep all the data in cache as we dont need to fill the dropdown again and again from database. How to achieve this by caching. Please guide

Answer 1

Suppose you have Cache varriable, then you have to convert it to DataTable,
DataTable tblCategories = (DataTable) Cache["Categories"];
and , then check, if still Datatable empty, then fetch from database using LoadCategoryInDropDownList() function which takes data from databse.
if (tblCategories == null)
{
tblCategories = new DataTable();
tblCategories=objDac.LoadCategoryInDropDownList();
// It inserts new row in filled datatable.
//This new row contains static data for user
//instruction Text such as" Select the Item"
DataRow dr=tblCategories.NewRow();
dr["CategoryID"]=0;
dr["CategoryName"]="--Select Item--";
tblCategories.Rows.InsertAt(dr,0);
//Cache The DataTable in a Cache Memory for duration of one hour...
Cache.Insert("Categories", tblCategories, null,
DateTime.Now.AddHours(1), Cache.NoSlidingExpiration);
}
then bind dropdown to datatable
DropDownList1.DataSource = tblCategories
DropDownList1.DataTextField ="A Descriptive Field from Table";
DropDownList1.DataValueField="A key / Value Field from Table";
DropDownList1.DataBind();
You can refer here http://www.codeproject.com/Articles/10033/A-generic-loading-of-data-in-a-DropDownList-using

Answer 2

Do you use particular cache framework?
.Net 4.5 has MemoryCache class you can use.
Example:
ObjectCache cache = MemoryCache.Default;
public Object GetCacheItem(string key)
{
return cache[key] as Object;
}
public void SaveCache(string key, Object value)
{
cache[key] = value;
}
public void RemoveCacheItem(string key)
{
if (cache.Contains(key))
cache.Remove(key);
}
Once you have your caching setup in a class, you can use it to cache your Agent lists. Then, load it to drop down list.
WARNING : Be very careful when using caching. Make sure you clear the cache at the end of certain life cycle. I have seen a case where IIS application pool using all of the memory in a server, so app pool has to be restarted every now and then.