Added OnceTemplate control.

gts/gts.csproj

@@ -3549,6 +3549,7 @@
       <DependentUpon>AddDressup.aspx</DependentUpon>
     </Compile>
     <Compile Include="src\FakeOpponentGenerator4.cs" />
+    <Compile Include="src\OnceTemplate.cs" />
     <Compile Include="src\RetinaImage.cs" />
     <Compile Include="src\RetinaImageBase.cs" />
     <Compile Include="test\BoxUp.aspx.cs">

gts/src/OnceTemplate.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Web;
+
+namespace PkmnFoundations.Web
+{
+    /// <summary>
+    /// Control which only renders once per unique key on a given page.
+    /// </summary>
+    public class OnceTemplate : System.Web.UI.WebControls.PlaceHolder
+    {
+        public OnceTemplate() : base()
+        {
+        }
+
+        public String Key { get; set; }
+
+        private HashSet<String> m_keys = null;
+        private HashSet<String> Keys
+        {
+            get
+            {
+                if (m_keys != null) return m_keys;
+                if (!Page.Items.Contains("pkmncfOnceTemplate"))
+                {
+                    m_keys = new HashSet<String>();
+                    Page.Items.Add("pkmncfOnceTemplate", m_keys);
+                }
+                else m_keys = (HashSet<String>)Page.Items["pkmncfOnceTemplate"];
+                return m_keys;
+            }
+        }
+
+        protected override void Render(System.Web.UI.HtmlTextWriter writer)
+        {
+            if (Keys.Contains(Key)) return;
+            Keys.Add(Key);
+            base.Render(writer);
+        }
+    }
+}