Ensure both numbers used in number operations are valid

Author: mythz

src/ServiceStack.Text/DynamicNumber.cs

@@ -430,6 +430,12 @@ public static IDynamicNumber GetNumber(object lhs, object rhs)
             if (lhs == null || rhs == null)
                 return null;
 
+            if (lhs is string lhsString && !TryParse(lhsString, out lhs))
+                return null;
+
+            if (rhs is string rhsString && !TryParse(rhsString, out rhs))
+                return null;
+
             if (!TryGetRanking(lhs.GetType(), out int lhsRanking) || !TryGetRanking(rhs.GetType(), out int rhsRanking))
                 return null;
 
@@ -438,26 +444,35 @@ public static IDynamicNumber GetNumber(object lhs, object rhs)
             return maxNumber;
         }
 
+        public static IDynamicNumber AssertNumbers(string name, object lhs, object rhs)
+        {
+            var number = GetNumber(lhs, rhs);
+            if (number == null)
+                throw new ArgumentException($"Invalid numbers passed to {name}: {lhs?.GetType().Name ?? "null"}, {rhs?.GetType().Name ?? "null"}");
+
+            return number;
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static object Add(object lhs, object rhs) => GetNumber(lhs, rhs).add(lhs, rhs);
+        public static object Add(object lhs, object rhs) => AssertNumbers(nameof(Add), lhs, rhs).add(lhs, rhs);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static object Sub(object lhs, object rhs) => GetNumber(lhs, rhs).sub(lhs, rhs);
+        public static object Sub(object lhs, object rhs) => AssertNumbers(nameof(Subtract), lhs, rhs).sub(lhs, rhs);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static object Subtract(object lhs, object rhs) => GetNumber(lhs, rhs).sub(lhs, rhs);
+        public static object Subtract(object lhs, object rhs) => AssertNumbers(nameof(Subtract), lhs, rhs).sub(lhs, rhs);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static object Mul(object lhs, object rhs) => GetNumber(lhs, rhs).mul(lhs, rhs);
+        public static object Mul(object lhs, object rhs) => AssertNumbers(nameof(Multiply), lhs, rhs).mul(lhs, rhs);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static object Multiply(object lhs, object rhs) => GetNumber(lhs, rhs).mul(lhs, rhs);
+        public static object Multiply(object lhs, object rhs) => AssertNumbers(nameof(Multiply), lhs, rhs).mul(lhs, rhs);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static object Div(object lhs, object rhs) => GetNumber(lhs, rhs).div(lhs, rhs);
+        public static object Div(object lhs, object rhs) => AssertNumbers(nameof(Divide), lhs, rhs).div(lhs, rhs);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static object Divide(object lhs, object rhs) => GetNumber(lhs, rhs).div(lhs, rhs);
+        public static object Divide(object lhs, object rhs) => AssertNumbers(nameof(Divide), lhs, rhs).div(lhs, rhs);
 
         public static bool TryParse(string strValue, out object result)
         {

tests/ServiceStack.Text.Tests/DynamicNumberTests.cs

@@ -165,5 +165,12 @@ public void Can_convert_between_string_and_char()
             Assert.That("a".ConvertTo<char>(), Is.EqualTo('a'));
         }
 
+        [Test]
+        public void Can_apply_operations_to_strings_containing_numbers()
+        {
+            var result = DynamicNumber.Add("1", "1");
+            Assert.That(result, Is.EqualTo(2));
+        }
+
     }
 }