source/Data/Data/ParameterCache.cs

@@ -0,0 +1,91 @@
+
+using System.Data;
+
+namespace GZTW.Data
+{
+    /// <summary>
+    /// <para>
+    /// Provides parameter caching services for dynamic parameter discovery of stored procedures.
+    /// Eliminates the round-trip to the database to derive the parameters and types when a command
+    /// is executed more than once.
+    /// </para>
+    /// </summary>
+    public class ParameterCache
+    {
+        private CachingMechanism cache = new CachingMechanism();
+
+        /// <summary>
+        /// <para>
+        /// Populates the parameter collection for a command wrapper from the cache 
+        /// or performs a round-trip to the database to query the parameters
+        /// </para>
+        /// </summary>
+        /// <param name="command">
+        /// <para>The command to add the parameters.</para>
+        /// </param>
+        /// <param name="parameterToken">
+        /// <para>The token used to delimit parameters.</para>
+        /// </param>
+        public void FillParameters(DBCommandWrapper command, char parameterToken)
+        {
+            if (AlreadyCached(command))
+            {
+                AddParametersFromCache(command);
+            }
+            else
+            {
+                command.DiscoverParameters(parameterToken);
+                IDataParameter[] copyOfParameters = CreateParameterCopy(command);
+
+                this.cache.AddParameterSetToCache(command.Command, copyOfParameters);
+            }
+
+            command.AssignParameterValues();
+        }
+
+        /// <summary>
+        /// <para>Empty the parameter cache</para>
+        /// </summary>
+        internal void Clear()
+        {
+            this.cache.Clear();
+        }
+
+        /// <summary>
+        /// <para>Checks to see if a cache entry exists for a specific command on a specific connection</para>
+        /// </summary>
+        /// <param name="command">
+        /// <para>The command to check.</para>
+        /// </param>
+        /// <returns>True if the parameters are already cached for the provided command, false otherwise</returns>
+        protected virtual bool AlreadyCached(DBCommandWrapper command)
+        {
+            return this.cache.IsParameterSetCached(command.Command);
+        }
+
+        /// <summary>
+        /// <para>Adds parameters to a command using the cache</para>
+        /// </summary>
+        /// <param name="command">
+        /// <para>The command to add the parameters.</para>
+        /// </param>
+        protected virtual void AddParametersFromCache(DBCommandWrapper command)
+        {
+            IDataParameter[] parameters = this.cache.GetCachedParameterSet(command.Command);
+
+            foreach (IDataParameter p in parameters)
+            {
+                command.Command.Parameters.Add(p);
+            }
+        }
+
+        private static IDataParameter[] CreateParameterCopy(DBCommandWrapper command)
+        {
+            IDataParameterCollection parameters = command.Command.Parameters;
+            IDataParameter[] parameterArray = new IDataParameter[parameters.Count];
+            parameters.CopyTo(parameterArray, 0);
+
+            return CachingMechanism.CloneParameters(parameterArray);
+        }
+    }
+}