[Mono-bugs] [Bug 67780][Wis] New - Mono's "Convert.ChangeType" behaving differently than MS.NET

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Changed by marianoa@itcsoluciones.com.

http://bugzilla.ximian.com/show_bug.cgi?id=67780

--- shadow/67780	2004-10-07 15:40:23.000000000 -0400
+++ shadow/67780.tmp.13788	2004-10-07 15:40:23.000000000 -0400
@@ -0,0 +1,97 @@
+Bug#: 67780
+Product: Mono: Class Libraries
+Version: unspecified
+OS: GNU/Linux [Other]
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: 
+Priority: Wishlist
+Component: System
+AssignedTo: mono-bugs@ximian.com                            
+ReportedBy: marianoa@itcsoluciones.com               
+QAContact: mono-bugs@ximian.com
+TargetMilestone: ---
+URL: 
+Cc: 
+Summary: Mono's "Convert.ChangeType" behaving differently than MS.NET
+
+I have this small function:
+
+public static object Parse(object from, Type toType, object defaultValue) {
+   try {
+       return Convert.ChangeType(from, toType);
+   } catch (Exception) {
+       return defaultValue;
+   }
+}
+
+I use it in Ms.net to convert between types. For example:
+
+int convertedInt = (int) Parse("123", typeof(int), 0);   // returns 123
+int convertedInt = (int) Parse("hello", typeof(int), 0); // returns   0
+int convertedInt = (int) Parse(null, typeof(int), 0);    // returns   0
+
+So far so good.
+
+Now with mono 1.0 the last statement generates an exception because Parse
+returns null instead of 0. That means that the conversion from null to int
+succeeds and the result is null (That's wrong right?).
+
+Steps to reproduce the problem:
+1. Compile the following source: ConvertTest.cs
+
+using System;
+using NUnit.Framework;
+
+[TestFixture]
+public class ConvertValueTypeToNull {
+    [Test]
+    public void testConvertValueTypes() {
+        // All are value types and cannot be converted to
+        // nulls. This function should return 0, not null.
+        Assert.IsNotNull(Parse(null, typeof(int), 0), "Wrong!");
+    }
+
+    public static object Parse(object from, 
+                               Type toType, 
+                               object defaultValue) {
+        try {
+            return Convert.ChangeType(from, toType);
+        } catch (Exception) {
+            return defaultValue;
+        }
+    }
+
+    public static void Main(string [] args) {
+        if (Parse(null, typeof(int), 0) == null) {
+            Console.WriteLine("Error!");
+        } else {
+            Console.WriteLine("Cool!");
+        } 
+    }
+}
+ 
+2. Compile the source with:
+
+$ mcs *.cs -target:exe -r:nunit.framework -debug+
+
+3. Run the program with:
+
+$ mono ConvertTest.exe
+
+4. Optionally it can be run as a test for nunit with:
+
+$ mono nunit-console.exe ConvertTest.exe
+
+Actual Results:
+ConvertTest.exe prints out "Error!".
+
+Expected Results:
+ConvertTest.exe should print out "Cool".
+
+How often does this happen? 
+Always.
+
+Additional Information:
+ConvertTest.exe works as expected in ms.net