Fixed netfx System.Net.Mail.Functional.Tests fails on non-English Windows (#28373)

Author: AlexRadch

src/System.Net.Mail/tests/Functional/SmtpExceptionTest.cs

@@ -12,6 +12,7 @@
 using System.Collections;
 using System.Runtime.Serialization;
 using System.Runtime.Serialization.Formatters;
+using System.Text.RegularExpressions;
 using Xunit;
 
 namespace System.Net.Mail.Tests
@@ -80,7 +81,12 @@ public void TestConstructorWithStringArgument()
             Assert.Equal(0, se.Data.Keys.Count);
             Assert.Null(se.InnerException);
             Assert.NotNull(se.Message);
-            Assert.NotEqual(-1, se.Message.IndexOf("'" + typeof(SmtpException).FullName + "'"));
+
+            // \p{Pi} any kind of opening quote https://www.compart.com/en/unicode/category/Pi
+            // \p{Pf} any kind of closing quote https://www.compart.com/en/unicode/category/Pf
+            // \p{Po} any kind of punctuation character that is not a dash, bracket, quote or connector https://www.compart.com/en/unicode/category/Po
+            Assert.Matches(@"[\p{Pi}\p{Po}]" + Regex.Escape(typeof(SmtpException).FullName) + @"[\p{Pf}\p{Po}]", se.Message);
+
             Assert.Equal(SmtpStatusCode.GeneralFailure, se.StatusCode);
         }
 
@@ -112,7 +118,12 @@ public void TestConstructorWithStatusCodeAndStringArgument()
             Assert.Equal(0, se.Data.Keys.Count);
             Assert.Null(se.InnerException);
             Assert.NotNull(se.Message);
-            Assert.NotEqual(-1, se.Message.IndexOf("'" + typeof(SmtpException).FullName + "'"));
+
+            // \p{Pi} any kind of opening quote https://www.compart.com/en/unicode/category/Pi
+            // \p{Pf} any kind of closing quote https://www.compart.com/en/unicode/category/Pf
+            // \p{Po} any kind of punctuation character that is not a dash, bracket, quote or connector https://www.compart.com/en/unicode/category/Po
+            Assert.Matches(@"[\p{Pi}\p{Po}]" + Regex.Escape(typeof(SmtpException).FullName) + @"[\p{Pf}\p{Po}]", se.Message);
+
             Assert.Equal((SmtpStatusCode)666, se.StatusCode);
         }