Move ProgramSetting into Feature

Wox.Infrastructure/StringEmptyConverter.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Windows.Data;
+using System.Windows.Markup;
+
+namespace Wox.Infrastructure
+{
+    public class StringEmptyConverter : MarkupExtension, IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+        {
+            return string.IsNullOrEmpty((string)value) ? parameter : value;
+        }
+
+        public object ConvertBack(
+              object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+        {
+            throw new NotSupportedException();
+        }
+
+
+        public override object ProvideValue(IServiceProvider serviceProvider)
+        {
+            return this;
+        }
+    }
+}