Fixed path resolution in HttpClient.ToFile for relative file names in web context

Issue:206567

Author: claudiamurialdo

dotnet/src/dotnetframework/GxClasses/Domain/GxHttpClient.cs

@@ -2001,7 +2001,7 @@ public void ToFile(string fileName)
 #if !NETCORE
 			if (HttpContext.Current != null)
 #endif
-			if (fileName.IndexOfAny(new char[] { '\\', ':' }) == -1)
+			if (!Path.IsPathRooted(fileName))
 				pathName = Path.Combine(GxContext.StaticPhysicalPath(), fileName);
 
 			if (ReceiveData != null)

dotnet/test/DotNetUnitTest/Domain/GxHttpClientTest.cs

@@ -189,6 +189,19 @@ public void HttpClientCookiesTest()
 
 		}
 
+		[Fact]
+		public void ToRelativeFile()
+		{
+			using (GxHttpClient client = new GxHttpClient())
+			{
+				client.Host = "localhost";
+				client.BaseURL = "/dummy/lem.txt";
+				client.Execute("GET", string.Empty);
+				client.ToFile("./lem.txt");
+				Assert.True(File.Exists(Path.Combine(Directory.GetCurrentDirectory(), "lem.txt")));
+			}
+		}
+
 #if !NETCORE
 		[Fact]
 		public void NoStoreHeader()