From 6e103cea63588102a5a7cfdfde732ab4bcbd3aa0 Mon Sep 17 00:00:00 2001
From: Michael Croes <mycroes@gmail.com>
Date: Fri, 28 Jul 2023 23:55:12 +0200
Subject: [PATCH] fix: Fix warnings in Struct

---
 S7.Net/Types/Struct.cs | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/S7.Net/Types/Struct.cs b/S7.Net/Types/Struct.cs
index 1e95508..6f29447 100644
--- a/S7.Net/Types/Struct.cs
+++ b/S7.Net/Types/Struct.cs
@@ -98,8 +98,8 @@ namespace S7.Net.Types
             int bytePos = 0;
             int bitPos = 0;
             double numBytes = 0.0;
-            object structValue = Activator.CreateInstance(structType);
-
+            object structValue = Activator.CreateInstance(structType) ??
+                throw new ArgumentException($"Failed to create an instance of the type {structType}.", nameof(structType));
 
             var infos = structValue.GetType()
 #if NETSTANDARD1_3
@@ -254,6 +254,14 @@ namespace S7.Net.Types
 
             foreach (var info in infos)
             {
+                static TValue GetValueOrThrow<TValue>(FieldInfo fi, object structValue) where TValue : struct
+                {
+                    var value = fi.GetValue(structValue) as TValue? ??
+                        throw new ArgumentException($"Failed to convert value of field {fi.Name} of {structValue} to type {typeof(TValue)}");
+
+                    return value;
+                }
+
                 bytes2 = null;
                 switch (info.FieldType.Name)
                 {
@@ -261,7 +269,7 @@ namespace S7.Net.Types
                         // get the value
                         bytePos = (int)Math.Floor(numBytes);
                         bitPos = (int)((numBytes - (double)bytePos) / 0.125);
-                        if ((bool)info.GetValue(structValue))
+                        if (GetValueOrThrow<bool>(info, structValue))
                             bytes[bytePos] |= (byte)Math.Pow(2, bitPos);            // is true
                         else
                             bytes[bytePos] &= (byte)(~(byte)Math.Pow(2, bitPos));   // is false
@@ -270,26 +278,26 @@ namespace S7.Net.Types
                     case "Byte":
                         numBytes = (int)Math.Ceiling(numBytes);
                         bytePos = (int)numBytes;
-                        bytes[bytePos] = (byte)info.GetValue(structValue);
+                        bytes[bytePos] = GetValueOrThrow<byte>(info, structValue);
                         numBytes++;
                         break;
                     case "Int16":
-                        bytes2 = Int.ToByteArray((Int16)info.GetValue(structValue));
+                        bytes2 = Int.ToByteArray(GetValueOrThrow<short>(info, structValue));
                         break;
                     case "UInt16":
-                        bytes2 = Word.ToByteArray((UInt16)info.GetValue(structValue));
+                        bytes2 = Word.ToByteArray(GetValueOrThrow<ushort>(info, structValue));
                         break;
                     case "Int32":
-                        bytes2 = DInt.ToByteArray((Int32)info.GetValue(structValue));
+                        bytes2 = DInt.ToByteArray(GetValueOrThrow<int>(info, structValue));
                         break;
                     case "UInt32":
-                        bytes2 = DWord.ToByteArray((UInt32)info.GetValue(structValue));
+                        bytes2 = DWord.ToByteArray(GetValueOrThrow<uint>(info, structValue));
                         break;
                     case "Single":
-                        bytes2 = Real.ToByteArray((float)info.GetValue(structValue));
+                        bytes2 = Real.ToByteArray(GetValueOrThrow<float>(info, structValue));
                         break;
                     case "Double":
-                        bytes2 = LReal.ToByteArray((double)info.GetValue(structValue));
+                        bytes2 = LReal.ToByteArray(GetValueOrThrow<double>(info, structValue));
                         break;
                     case "String":
                         S7StringAttribute? attribute = info.GetCustomAttributes<S7StringAttribute>().SingleOrDefault();
@@ -298,8 +306,8 @@ namespace S7.Net.Types
 
                         bytes2 = attribute.Type switch
                         {
-                            S7StringType.S7String => S7String.ToByteArray((string)info.GetValue(structValue), attribute.ReservedLength),
-                            S7StringType.S7WString => S7WString.ToByteArray((string)info.GetValue(structValue), attribute.ReservedLength),
+                            S7StringType.S7String => S7String.ToByteArray((string?)info.GetValue(structValue), attribute.ReservedLength),
+                            S7StringType.S7WString => S7WString.ToByteArray((string?)info.GetValue(structValue), attribute.ReservedLength),
                             _ => throw new ArgumentException("Please use a valid string type for the S7StringAttribute")
                         };
                         break;