diff --git a/csharp_fundamentals/5_working_with_reference_types_and_value_types.md b/csharp_fundamentals/5_working_with_reference_types_and_value_types.md
index eb3a918..57fc012 100644
--- a/csharp_fundamentals/5_working_with_reference_types_and_value_types.md
+++ b/csharp_fundamentals/5_working_with_reference_types_and_value_types.md
@@ -78,4 +78,20 @@ To **Pass-parameter-by-reference**, use `ref/out param` in both function definit
         }
 ```
 
-Not very often use.
\ No newline at end of file
+Not very often use.
+
+## Working with Value Types & Value Type Parameters
+
+Reference:
+* [Value types (C# reference)](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/value-types)
+* [Types (C# Programming Guide)](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/types/)
+
+## Looking for Reference Types & Value Types & The Special Case of Strings in .NET
+
+Differentiate btw Value & Reference:
+* When variable is created by `class`, it's Reference type
+* When variable is created by `struct`, it's Value type
+
+How to check whether it's reference or value type:
+* Place cursor in VSCode to type, Press `F12`, we can see metadata for the type. It will show whether it's `struct` or `class`
+* The only exception is `String`, it's a reference type but often behave like a value type (i.e. passed as value in function by default)
\ No newline at end of file