Добавил тест для прямоугольника

StructureHelperLogics/NdmCalculations/Materials/IPrimitiveMaterial.cs

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+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace StructureHelperLogics.NdmCalculations.Materials
+{
+    public interface IPrimitiveMaterial
+    {
+        string Id { get;}
+        MaterialTypes MaterialType { get; }
+        string ClassName { get; }
+        double Strength { get; }
+    }
+}

StructureHelperLogics/NdmCalculations/Materials/MaterialTypes.cs

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+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace StructureHelperLogics.NdmCalculations.Materials
+{
+    public enum MaterialTypes
+    {
+        Concrete,
+        Reinforcement,
+        //Steel,
+        //CarbonFiber,
+    }
+}

StructureHelperLogics/NdmCalculations/Materials/PrimitiveMaterial.cs

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+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace StructureHelperLogics.NdmCalculations.Materials
+{
+    public class PrimitiveMaterial : IPrimitiveMaterial
+    {
+        public string Id { get; }
+        public MaterialTypes MaterialType { get; set; }
+        public string ClassName { get; set; }
+        public double Strength { get; set; }
+
+        public PrimitiveMaterial()
+        {
+            Id = Convert.ToString(Guid.NewGuid());
+        }
+    }
+}