Add curvature calculator

StructureHelperCommon/Infrastructures/Exceptions/StructureHelperNullReferenceException.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace StructureHelperCommon.Infrastructures.Exceptions
+{
+    public class StructureHelperNullReferenceException : StructureHelperException
+    {
+        public StructureHelperNullReferenceException(string errorString) : base(errorString)
+        {
+        }
+
+        public StructureHelperNullReferenceException(Exception ex) : base(ex)
+        {
+        }
+    }
+}