Lookup table

David Smith

16y3.4k.NET

I want to basically do a look up table in code, whether its array of strings , enumeration, or dictionary, im trying to find the best way.
I want to do lookup base off of the code, so when I extact data in and I get a string that is "000", I want to say "000" is cat. which is the best way to do this

item code

cat , "000"
dog , "001"
mice, "01A"

Hi you guys what do you think is the best way to do this, right now my lookup table is in the database and im pulling from the database which is cool, but im trying to limit the database from doing all the work.

9 Replies

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David Smith16y ago
Hey guys

Thanks , instead I just kept it simple, i was trying to broaden my c sharp vocabulary i did something like this instead
This works perfect I cut down a minute in a half when processing files, Im trying to stay from opening the database as much as possible
```
commonFunctions.initDictionary();
string value = commonFunctions.ValidAnimalsNames("00AA");
```
public class commonAnimals
{
    static private Dictionary<string, string> ValidAnimalsNames= new Dictionary<string,string>();
    static public void initDictionary()
    {
        ValidAnimalsNames.Add("0000", "CAT");
        ValidAnimalsNames.Add("00AA", "DOG");
        ValidAnimalsNames.Add("0002", "BEAR");
    }

    static public string GetValidAnimalsName(string key)
    {
        string value = string.Empty;

        if (ValidAnimalsNames.ContainsKey(key))
        {
            value =  ValidAnimalsNames[key];
        }

        return value;
    }
}
Sam Hobbs16y ago
If you create the TableAdapter once each execution, the performance should be quite acceptable. For the number of records you are processing, it is unlikely that you will get better performance by spending any significant more of your time.
David Smith16y ago
check your email!! so which do you think is faster connecting to the database and retrieving info or just handling the lookup in code
Sam Hobbs16y ago
Create an instance of the TableAdapter once during execution and use the same instance during execution. If you are not doing that everywhere possible then it is quite possible you can significantly improve performance by doing that.
David Smith16y ago
I'm trying to minimize using the database as much as possible, the files are being process to slow, then we have to mant tables in the database, so i want to limit make the database much smaller,
Sam Hobbs16y ago
Create a TableAdapter for the table then do a lookup using the TableAdapter; your code already has samples of doing that. You could convert the TableAdapter results to a collection such as a Dictionary but that is probably not necessary.

If the identifying code is a sequential number such as shown in your latest sample code, then you could create an array of strings (Descriptions) and then use the subscript to get a specific Description. If the code is not sequential but it is (or could be) an integer, then you could use a Dictionary or a collection such as that. You could use a Dictionary or a collection such as that even if the key is a string.
Felipe Ramos16y ago
   public enum ValidAnimals
   {
   [Description("BEAR")]
   A = 0x0000, //is there a way to get the description base off of the 0x0000
   [Description("DOG ")]
   B = 0x0001,
   [Description("CAT ")]
   C = 0x0002,
   }

   public static string GetName(ValidAnimals value)
   {
   // Get the type
   Type type = value.GetType();

   // Get fieldinfo for this type
   FieldInfo fieldInfo = type.GetField(value.ToString());

   // Get the stringvalue attributes
   DescriptionAttribute[] attribs = fieldInfo.GetCustomAttributes(
   typeof(DescriptionAttribute), false) as DescriptionAttribute[];

   // Return the first if there was a match.
   return attribs.Length > 0 ? attribs[0].Description : null;
   }

   static void Main(string[] args)
   {
   Console.WriteLine(GetName(ValidAnimals.A));
   Console.ReadLine();
   }
David Smith16y ago
lolol a lil complicated for me what if i do something like this, Im having a lil trouble with it, can you tell me what im doing wrong

public enum ValidAnimals
    {
      [Description("BEAR")] A = 0x0000,     //is there a way to get the description base off of the 0x0000
      [Description("DOG ")] B = 0x0001,
      [Description("CAT ")] C = 0x0002,
    }

    public string GetName(string Value)
    {Value ="0000";
      FieldInfo fi = stringValue.GetType().GetField(Value);
      DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
      return (attributes.Length > 0) ? attributes[0].Description : stringValue;
    }
Felipe Ramos16y ago
If you are trying to limit the database calls and your lookup table doesn't change often you can Cache the result for as long as you want. It would work something like

public Dataset GetLookupTable()
{
if (Cache.Exists("AnimalLookup"))
return Cache.GetFromCache("AnimalLookup") as Dataset;
else
{
Dataset result = CallSQL;
Cache.SetCache("AnimalLookup",result, DateTime.Now.AddDays(30));
}
}

The other is to have a Hashtable or Dirctionary at the application level.

Here is the caching class using .net
public class Cache
   {
   private static System.Web.Caching.Cache cache = null;
   private static TimeSpan timeSpan = new TimeSpan(31, 0, 0, 0);

   static Cache()
   {
   try
   {
   cache = HttpContext.Current.Cache;
   }
   catch (Exception)
   {
   cache = new System.Web.Caching.Cache();
   }
   }

   public static object GetFromCache(string cache_key)
   {
   return cache.Get(cache_key);
   }

   public static List GetCacheKeys()
   {
   List keys = new List(20);
   IDictionaryEnumerator ca = cache.GetEnumerator();
   while (ca.MoveNext())
   keys.Add(ca.Key.ToString());
   return keys;
   }

   public static void SetCache(string cache_key, object cache_object)
   {
   SetCache(cache_key, cache_object, timeSpan);
   }

   public static void SetCache(string cache_key, object cache_object, DateTime expiration)
   {
   SetCache(cache_key, cache_object, expiration, CacheItemPriority.Normal);
   }

   public static void SetCache(string cache_key, object cache_object, TimeSpan expiration)
   {
   SetCache(cache_key, cache_object, expiration, CacheItemPriority.Normal);
   }

   public static void SetCache(string cache_key, object cache_object, DateTime expiration, CacheItemPriority priority)
   {
   try
   {
   cache.Insert(cache_key, cache_object, null, expiration,
   System.Web.Caching.Cache.NoSlidingExpiration, priority, null);
   }
   catch (Exception) { }
   }

   public static void SetCache(string cache_key, object cache_object, TimeSpan expiration, CacheItemPriority priority)
   {
   cache.Insert(cache_key, cache_object, null, System.Web.Caching.Cache.NoAbsoluteExpiration,
   expiration, priority, null);
   }

   public static void Delete(string cache_key)
   {
   if (Exists(cache_key))
   cache.Remove(cache_key);
   }

   public static bool Exists(string cache_key)
   {
   try
   {
   if (cache.Get(cache_key) != null)
   return true;
   return false;
   }
   catch (Exception) { return false; }
   }

   public static void Flush()
   {
   foreach (string key in GetCacheKeys())
   {
   Delete(key);
   }
   }
   }