diff --git a/vs4win/Chapter04/Instrumenting/Program.Methods.cs b/vs4win/Chapter04/Instrumenting/Program.Methods.cs
new file mode 100644
index 0000000..9b7187b
--- /dev/null
+++ b/vs4win/Chapter04/Instrumenting/Program.Methods.cs
@@ -0,0 +1,17 @@
+using System.Diagnostics; // Trace
+using System.Runtime.CompilerServices; // [Caller...] attributes
+
+partial class Program
+{
+  static void LogSourceDetails(
+    bool condition,
+    [CallerMemberName] string member = "",
+    [CallerFilePath] string filepath = "", 
+    [CallerLineNumber] int line = 0,
+    [CallerArgumentExpression(nameof(condition))] string expression = "")
+  {
+    Trace.WriteLine(string.Format(
+      "[{0}]\n  {1} on line {2}. Expression: {3}",
+      filepath, member, line, expression));
+  }
+}
diff --git a/vs4win/Chapter04/Instrumenting/Program.cs b/vs4win/Chapter04/Instrumenting/Program.cs
index 3460f77..4eaf455 100644
--- a/vs4win/Chapter04/Instrumenting/Program.cs
+++ b/vs4win/Chapter04/Instrumenting/Program.cs
@@ -40,4 +40,7 @@ Trace.WriteLineIf(ts.TraceWarning, "Trace warning");
 Trace.WriteLineIf(ts.TraceInfo, "Trace information");
 Trace.WriteLineIf(ts.TraceVerbose, "Trace verbose");
 
-Console.ReadLine();
\ No newline at end of file
+int unitsInStock = 12;
+LogSourceDetails(unitsInStock > 10);
+
+Console.ReadLine();
diff --git a/vscode/Chapter04/Instrumenting/Program.Methods.cs b/vscode/Chapter04/Instrumenting/Program.Methods.cs
new file mode 100644
index 0000000..9b7187b
--- /dev/null
+++ b/vscode/Chapter04/Instrumenting/Program.Methods.cs
@@ -0,0 +1,17 @@
+using System.Diagnostics; // Trace
+using System.Runtime.CompilerServices; // [Caller...] attributes
+
+partial class Program
+{
+  static void LogSourceDetails(
+    bool condition,
+    [CallerMemberName] string member = "",
+    [CallerFilePath] string filepath = "", 
+    [CallerLineNumber] int line = 0,
+    [CallerArgumentExpression(nameof(condition))] string expression = "")
+  {
+    Trace.WriteLine(string.Format(
+      "[{0}]\n  {1} on line {2}. Expression: {3}",
+      filepath, member, line, expression));
+  }
+}
diff --git a/vscode/Chapter04/Instrumenting/Program.cs b/vscode/Chapter04/Instrumenting/Program.cs
index 3460f77..4eaf455 100644
--- a/vscode/Chapter04/Instrumenting/Program.cs
+++ b/vscode/Chapter04/Instrumenting/Program.cs
@@ -40,4 +40,7 @@ Trace.WriteLineIf(ts.TraceWarning, "Trace warning");
 Trace.WriteLineIf(ts.TraceInfo, "Trace information");
 Trace.WriteLineIf(ts.TraceVerbose, "Trace verbose");
 
-Console.ReadLine();
\ No newline at end of file
+int unitsInStock = 12;
+LogSourceDetails(unitsInStock > 10);
+
+Console.ReadLine();