Refactoring: add some button icons

StructureHelperCommon/Models/Forces/IForceCombinationFromFile.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelperCommon.Models.Forces
+{
+    internal interface IForceCombinationFromFile : IForceAction
+    {
+        List<IForceFileProperty> ForceFiles { get; set; }
+    }
+}