Add Mail editor (WIP)

Update Drop editor indexes

Source/GrasscutterTools/Utils/UIUtil.cs

@@ -1,4 +1,5 @@
-using System.Threading.Tasks;
+using System.Linq;
+using System.Threading.Tasks;
 using System.Windows.Forms;
 
 namespace GrasscutterTools.Utils
@@ -19,5 +20,20 @@ namespace GrasscutterTools.Utils
             btn.Text = t;
             btn.Enabled = true;
         }
+
+        /// <summary>
+        /// 列表过滤
+        /// </summary>
+        /// <param name="listBox">列表控件</param>
+        /// <param name="source">数据源</param>
+        /// <param name="filter">过滤内容</param>
+        public static void ListBoxFilter(ListBox listBox, string[] source, string filter)
+        {
+            filter = filter.Trim();
+            listBox.BeginUpdate();
+            listBox.Items.Clear();
+            listBox.Items.AddRange(source.Where(n => n.Contains(filter)).ToArray());
+            listBox.EndUpdate();
+        }
     }
 }