Unit constants was added

Infrastructure/UI/Converters/Units/Stress.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using System.Windows.Data;
+
+namespace StructureHelper.Infrastructure.UI.Converters.Units
+{
+    internal class Stress : UnitBase
+    {
+        private double coeffficient = UnitConstatnts.Stress;
+
+        public override string unitName { get => "Stress"; }
+
+        public override object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            double val;
+            if (value != null) { val = (double)value; }
+            else { throw new Exception($"{unitName} value is null"); }
+            val *= coeffficient;
+            return val;
+        }
+
+        public override object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            double val;
+            if (value != null)
+            {
+                var strVal = value as string;
+                double.TryParse(strVal, out val);
+            }
+            else { throw new Exception($"{unitName} value is null"); }
+            val /= coeffficient;
+            return val;
+        }
+    }
+}