protected override Dictionary <TKey, string> GetDictionaryToCache(LookupDataByKey <TKey> lookupDataByKey)
{
string sql = $"SELECT * FROM {lookupDataByKey.TableName} (NOLOCK)";
DataTable dataTable = ExecuteSql(sql, lookupDataByKey.DataSource);
string columnNameOfPrimaryKey = lookupDataByKey.ColumnNameOfPrimaryKey ?? dataTable.Columns[0].ColumnName;
string columnNameOfField = lookupDataByKey.ColumnNameOfField ?? dataTable.Columns[1].ColumnName;
return(dataTable.AsEnumerable()
.ToDictionary(dr => (TKey)dr[columnNameOfPrimaryKey], dr => dr[columnNameOfField] == DBNull.Value ? null : dr[columnNameOfField].ToString()));
}
private string GetLookupValue(LookupDataByKey <TKey> lookupDataByKey, string cacheKey)
{
Dictionary <TKey, string> lookupValues =
_cache.GetOrSet(cacheKey, () => GetDictionaryToCache(lookupDataByKey), GetCacheTimeoutInHours(lookupDataByKey));
KeyValuePair <TKey, string> keyValuePair = lookupValues
.SingleOrDefault(kvp => Convert.ToInt64(kvp.Key) == Convert.ToInt64(lookupDataByKey.Key));
if (keyValuePair.Equals(default(KeyValuePair <TKey, string>)))
{
return(null);
}
return(keyValuePair.Value);
}
/// <summary>
/// This is the protected AutoMapper method called within a mapper class when using opt.ResolveUsing()
/// In this class, GetLookupValue() is called twice as a type of self-healing mechanism whereby if we can't find the value the first time, we'll clear the cache and try again
/// This is because it's possible for a new value to be inserted into a lookup table after this cache is loaded but before the cache timeout expires
/// If we don't find what we're looking for, we make a one-time assumption that the cache could be out of sync, so we refresh the cache and try one more time to get the expected value
/// </summary>
public override string Resolve(object source, object destination, LookupDataByKey <TKey> sourceMember, string destMember, ResolutionContext context)
{
if (sourceMember == null || EqualityComparer <TKey> .Default.Equals(sourceMember.Key, default(TKey)))
{
return(null);
}
string cacheKey = GetCacheKey(sourceMember.TableName);
string result = GetLookupValue(sourceMember, cacheKey);
if (result == null)
{
_cache.Remove(cacheKey);
result = GetLookupValue(sourceMember, cacheKey);
}
return(result);
}
/// <summary>
/// Exposing the AutoMapper trigger method allows clients to use this resolver outside of an AutoMapper as well
/// </summary>
public string Resolve(LookupDataByKey <TKey> lookupDataByKey)
{
return(Resolve(null, null, lookupDataByKey, null, null));
}
protected abstract Dictionary <TKey, string> GetDictionaryToCache(LookupDataByKey <TKey> lookupDataByKey);
