fix doc

docs/Rules/MA0161.md

@@ -1 +1,43 @@
-# MA0161 - UseShellExecute must be explicitly set
+# MA0161 - UseShellExecute must be explicitly set
+
+Detects when `Process.Start` is called without specifying the value of `UseShellExecute`.
+
+Specifying the value is important because:
+- The default value for this property is `true` on .NET Framework apps and `false` on .NET Core apps. It's a common issue when migrating a desktop app from .NET Framework to .NET Core.
+- It must be set to to `false` when redirecting I/O. Otherwise you'll get an issue at runtime.
+
+
+````c#
+using System.Diasgnostics;
+
+// Non compliant
+
+Process.Start("cmd"); // Intent is not clear if you want to use ShellExecute or not
+
+Process.Start("https://www.meziantou.net/"); // Will fail on .NET Core apps
+
+Process.Start(new ProcessStartInfo("cmd")
+{
+    RedirectStandardOutput = true,
+    UseShellExecute = true,
+});  // It will throw with error "UseShellExecute must be set to false when redirecting I/O"
+
+Process.Start(new ProcessStartInfo("cmd")
+{
+    RedirectStandardOutput = true,
+});  // It will throw with error "UseShellExecute must be set to false when redirecting I/O" on .NET Framework apps
+
+// Compliant
+
+Process.Start(new ProcessStartInfo("https://www.meziantou.net/")
+{
+    UseShellExecute = true,
+});
+
+Process.Start(new ProcessStartInfo("cmd")
+{
+    RedirectStandardOutput = true,
+    UseShellExecute = false,
+});
+
+````