feat: commit content which I don't know when I create them

BallanceTasEditor/Converters/StringifyConverter.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows;
+using System.Windows.Data;
+
+namespace BallanceTasEditor.Converters {
+
+    [ValueConversion(typeof(int?), typeof(string))]
+    public class StringifyIntegerConverter : IValueConverter {
+        public static StringifyIntegerConverter Instance = new StringifyIntegerConverter();
+
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
+            if (value is null) {
+                return "";
+            } else if (value is int iv) {
+                return iv.ToString();
+            } else {
+                return DependencyProperty.UnsetValue;
+            }
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) {
+            if (value is string s) {
+                if (int.TryParse(s, out int iv)) return iv;
+                else return null;
+            } else {
+                return DependencyProperty.UnsetValue;
+            }
+        }
+    }
+}