You want to save often used Strings. You have several Approaches. My Preferred Approach is adding a constants.cs with static string:
internal class Constants
{
internal static String Id = "@C_Id";
}
you can use it later by calling
Cmd.Parameters.Add(Constants.Id, SqlDbType.Int).Value = UI.C_Id;
Another Approach is using an enum with the ToString() Method. A Dictionary is not the best way, since it always has to be initialized first.
Hope i could help