From 1afd59325fc31f31bb7793184fcc844851ab1fe6 Mon Sep 17 00:00:00 2001
From: Christian Kratky <christian.kratky@googlemail.com>
Date: Mon, 8 Apr 2019 22:29:46 +0200
Subject: [PATCH] Add validations for client options builder.

---
 Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs b/Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs
index ca9c700e..20e008a3 100644
--- a/Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs
+++ b/Source/MQTTnet/Client/Options/MqttClientOptionsBuilder.cs
@@ -15,6 +15,11 @@ namespace MQTTnet.Client.Options
 
         public MqttClientOptionsBuilder WithProtocolVersion(MqttProtocolVersion value)
         {
+            if (value == MqttProtocolVersion.Unknown)
+            {
+                throw new ArgumentException("Protocol version is invalid.");
+            }
+
             _options.ProtocolVersion = value;
             return this;
         }