String != string for ​Xml​Serializer

XmlSerializer serializer = new XmlSerializer(typeof(string[]));

That's weird. Can you give an example that shows this incompatibility?

JohnAskew wrote:



XmlSerializer serializer = new XmlSerializer(typeof(string[]));

XmlSerializer serializer = new XmlSerializer(typeof(String[]));

These are not interchangeable.

Outside of XmlSerializer, where else do these types conflict?

Type type1 = typeof(string[]);
Type type2 = typeof(String[]);
Console.WriteLine("type1=" + type1);
Console.WriteLine("type2=" + type2);
Console.WriteLine("ref equals=" +
    Object.ReferenceEquals(type1, type2));

Run it and you should get this, which supports what I've said above about "string" just being an alias to the "String" class:

type1=System.String[]
type2=System.String[]
ref equals=True

Edit: To drive the point home, the two statements below should be identical. You should be able to look at the IL with ildasm to confirm this.

JohnAskew wrote:



XmlSerializer serializer = new XmlSerializer(typeof(string[]));

XmlSerializer serializer = new XmlSerializer(typeof(String[]));

Use a class library on client and web service sides, return String[] in a web method.

The web service reference generates (wsdl) classes for xml transfer.

I think this is where the two types are disconnected.

Try for yourself changing String[] to string[] on the client side and you will see the XmlSerializer cannot resolve them. The issue is mapping back from the generated classes and the class library classes. XmlSerializer can't map String[] to string[].

That's all.

I know string is an alias for String, etc..., it's an XmlSerializer issue!

JohnAskew wrote:

I know string is an alias for String, etc..., it's an XmlSerializer issue!

Nah, just found it odd yesterday debugging...

This works on my machine:

using System;
using System.Xml.Serialization;

namespace TestStringType {
    class Program {
        static void Main(string[] args) {
            bool a = Object.ReferenceEquals(typeof(string[]), typeof(String[]));
            Console.WriteLine(a);

            XmlSerializer serializer = new XmlSerializer(typeof(string[]));
            XmlSerializer serializer2 = new XmlSerializer(typeof(String[]));

            String[] s = { "Hi", "There", "Foo", "Bar" };

            Console.WriteLine("string[] serializer:");
            serializer.Serialize(Console.Out, s);
            Console.WriteLine("\n\nString[] serializer:");
            serializer2.Serialize(Console.Out, s);

            Console.ReadKey();
        }
    }
}

 
Output:

True
string[] serializer:
<?xml version="1.0" encoding="IBM437"?>
<ArrayOfString xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="
http://www.w3.org/2001/XMLSchema">
  <string>Hi</string>
  <string>There</string>
  <string>Foo</string>
  <string>Bar</string>
</ArrayOfString>

String[] serializer:
<?xml version="1.0" encoding="IBM437"?>
<ArrayOfString xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="
http://www.w3.org/2001/XMLSchema">
  <string>Hi</string>
  <string>There</string>
  <string>Foo</string>
  <string>Bar</string>
</ArrayOfString>

edit:  You're not on .Net 1.1, are you?

string was an alias to String in 1.1 and 1.0 too. Something's really really weird

Doesn't seem strange to me.

Don't forget that the string->String alias is in C# ONLY. Its a language feature and has nothing to do with .Net.
So if you are e.g. manually changing WSDL or other Markup it seems logical that "String" is no longer equal to "string".