Andrew Pallant

Software & Web Developer

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Caching Locally

Physical Link: Caching Locally

One of the applications I have been working recently is a windows based application. Most things that the user keys into the system results in a database hit validation. To cut back on this I have implemented classes that assist in caching to the user’s local system. Based on the user’s habits, it will cache what the user uses commonly.

I am using a datatable in this example, but you could use a dictionary object. Should you choose to use a dictionary object, you could use LINQ to query the object. You could also make the caching class an extension which could cut down on some code an make it a little cleaner.

At the end of the day, this is one example only of what could be done.

Class Example

public class CurrencyCodes
private static CurrencyCodes _instance; // Instance Of Self

private static DataTable dt = new DataTable("CurrencyCodes");

public static CurrencyCodes Instance
if (_instance == null)
_instance = new CurrencyCodes();
return _instance;

private CurrencyCodes()
dt.Columns.Add("CurrencyCode", typeof(String));
dt.Columns.Add("LastUpdated", typeof(DateTime));

public String Search(String value)
DataRow[] rows = dt.Select("CurrencyCode='" + value + "'");
if (rows.Count() == 1) return value;
return "";

public void Add(String value)
DataRow row = dt.NewRow();
row["CurrencyCode"] = value;
row["LastUpdated"] = DateTime.Now;

public void ClearCache()

public void LoadCache(String xml)
StringReader theReader = new StringReader(xml);

public String SaveCache()
using (MemoryStream ms = new MemoryStream())
ms.Position = 0;

StreamReader sr = new StreamReader(ms, System.Text.Encoding.UTF8);

return sr.ReadToEnd();

Calling the class

if (!Directory.Exists("YourSoftwareCache"))

if (File.Exists("CurrencyCodes.XML"))

CachedCurrencyCodes cachedCurrencyCodes = CachedCurrencyCodes.Instance;
CurrencyCode = cachedCurrencyCodes.Search(Criteria);

Note Comments have been stripped to clean up the posting. Always Comment Your Code.

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Categories: C#, Caching

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