CosmosClientOptions: Adds validation for ApplicationName

Microsoft.Azure.Cosmos/src/CosmosClientOptions.cs

@@ -90,7 +90,28 @@ public CosmosClientOptions()
         /// <remarks>
         /// Setting this property after sending any request won't have any effect.
         /// </remarks>
-        public string ApplicationName { get; set; }
+        /// 
+        private string applicationName;
+        public string ApplicationName
+        {
+            get => this.applicationName;
+            set
+            {
+                HttpClient httpClient = new HttpClient();
+                try
+                {
+                    using System.Net.Http.Headers.HttpHeaderParser.ParseValue(value);
+                }
+                catch (FormatException formatException)
+                {
+                    ApplicationNameException e = new ApplicationNameException(value);//new exception i was thinking of making
+                    throw e;
+                }
+
+                this.applicationName = value;
+
+            }
+        }
 
         /// <summary>
         /// Get or set session container for the client

Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.EmulatorTests/ClientTests.cs

@@ -863,6 +863,33 @@ public async Task HttpClientConnectionLimitTest()
                 $"Before connections: {JsonConvert.SerializeObject(excludeConnections)}; After connections: {JsonConvert.SerializeObject(afterConnections)}");
         }
 
+        [TestMethod]
+        public void InvalidApplicationNameCatchTest()
+        {
+            try
+            {
+                string invalidName = "<<";
+                Console.WriteLine("Invalid string:\t" + invalidName);
+                CosmosClient cosmosClient = new CosmosClient(
+                    ConfigurationManager.AppSettings["GatewayEndpoint"],
+                    ConfigurationManager.AppSettings["MasterKey"],
+                    new CosmosClientOptions
+                    {
+                        ApplicationName = invalidName
+                    }
+                );
+                Console.WriteLine("String actually vaild");
+            }
+            catch(Exception exc)
+            {
+                Console.WriteLine("\n\n\n\n__________\n\nString was invalid, exception below");
+                Console.WriteLine(exc);
+                Console.WriteLine("\n_____\n\n\n\n");
+            }
+
+            //Assert.ThrowsExceptionAsync<exception type>(async () => {code in here});
+
+        }
         public static IReadOnlyList<string> GetActiveConnections()
         {
             string testPid = Process.GetCurrentProcess().Id.ToString();