I have a service built using Preview 2 of the WCF REST starter kit, but I've run into an issue with passing around XML-styled data in the calls. Here's my request object:
[DataContract(Namespace = "")]
public class ServiceRequest
{
[DataMember]
public string ContentText { get; set; }
[DataMember]
public string ApiKey { get; set; }
}
Everything works fine until you throw '' in there. Is there a to encapsulate the ContentText property in a CDATA or something similar?
Marc Gravell has a solution here for serializing CDATA sections.
I have copied the code here for posterity.
updated: the previous example did not generate a valid schema, the XmlSchemaProviderAttribute and accompanying method will generate "xs:string" which works [more...]
using System;
using System.IO;
using System.Runtime.Serialization;
using System.Xml;
using System.Xml.Serialization;
using System.ComponentModel;
[XmlSchemaProvider("GenerateSchema")]
public sealed class CDataWrapper : IXmlSerializable
{
// implicit to/from string
public static implicit operator string(CDataWrapper value)
{
return value == null ? null : value.Value;
}
public static implicit operator CDataWrapper(string value)
{
return value == null ? null : new CDataWrapper { Value = value };
}
public System.Xml.Schema.XmlSchema GetSchema()
{
return null;
}
// return "xs:string" as the type in scheme generation
public static XmlQualifiedName GenerateSchema(XmlSchemaSet xs)
{
return XmlSchemaType.GetBuiltInSimpleType(XmlTypeCode.String).QualifiedName;
}
// "" => <Node/>
// "Foo" => <Node><![CDATA[Foo]]></Node>
public void WriteXml(XmlWriter writer)
{
if (!string.IsNullOrEmpty(Value))
{
writer.WriteCData(Value);
}
}
// <Node/> => ""
// <Node></Node> => ""
// <Node>Foo</Node> => "Foo"
// <Node><![CDATA[Foo]]></Node> => "Foo"
public void ReadXml(XmlReader reader)
{
if (reader.IsEmptyElement)
{
Value = "";
}
else
{
reader.Read();
switch (reader.NodeType)
{
case XmlNodeType.EndElement:
Value = ""; // empty after all...
break;
case XmlNodeType.Text:
case XmlNodeType.CDATA:
Value = reader.ReadContentAsString();
break;
default:
throw new InvalidOperationException("Expected text/cdata");
}
}
}
// underlying value
public string Value { get; set; }
public override string ToString()
{
return Value;
}
}
// example usage
[DataContract(Namespace="http://myobjects/")]
public sealed class MyType
{
public string SomeValue { get; set; }
[DataMember(Name = "SomeValue", EmitDefaultValue = false)]
private CDataWrapper SomeValueCData
{
get { return SomeValue; }
set { SomeValue = value; }
}
public string EmptyTest { get; set; }
[DataMember(Name = "EmptyTest", EmitDefaultValue = false)]
private CDataWrapper EmptyTestCData
{
get { return EmptyTest; }
set { EmptyTest = value; }
}
public string NullTest { get; set; }
[DataMember(Name = "NullTest", EmitDefaultValue = false)]
private CDataWrapper NullTestCData
{
get { return NullTest ; }
set { NullTest = value; }
}
}
// test rig
static class Program
{
static void Main()
{
DataContractSerializer dcs = new DataContractSerializer(typeof(MyType));
StringWriter writer = new StringWriter();
using (XmlWriter xw = XmlWriter.Create(writer))
{
MyType foo = new MyType
{
SomeValue = @"&<t\d",
NullTest = null,
EmptyTest = ""
};
ShowObject("Original", foo);
dcs.WriteObject(xw, foo);
xw.Close();
}
string xml = writer.ToString();
ShowObject("Xml", xml);
StringReader reader = new StringReader(xml);
using (XmlReader xr = XmlReader.Create(reader))
{
MyType bar = (MyType) dcs.ReadObject(xr);
ShowObject("Recreated", bar);
}
}
static void ShowObject(string caption, object obj)
{
Console.WriteLine();
Console.WriteLine("** {0} **", caption );
Console.WriteLine();
if (obj == null)
{
Console.WriteLine("(null)");
}
else if (obj is string)
{
Console.WriteLine((string)obj);
}
else
{
foreach (PropertyDescriptor prop in TypeDescriptor.GetProperties(obj))
{
Console.WriteLine("{0}:\t{1}", prop.Name, prop.GetValue(obj) ?? "(null)");
}
}
}
}
VB conversion of the CDataWrapper in the accepted answer:
Imports System
Imports System.IO
Imports System.Runtime.Serialization
Imports System.Xml
Imports System.Xml.Schema
Imports System.Xml.Serialization
Imports System.ComponentModel
Public Class CDataWrapper
Implements IXmlSerializable
'underlying value
Public Property Value As String
'Implicit to/from string
Public Shared Widening Operator CType(ByVal value As CDataWrapper) As String
If value Is Nothing Then
Return Nothing
Else
Return value.Value
End If
End Operator
Public Shared Widening Operator CType(value As String) As CDataWrapper
If value Is Nothing Then
Return Nothing
Else
Return New CDataWrapper() With {.Value = value}
End If
End Operator
Public Function GetSchema() As XmlSchema Implements IXmlSerializable.GetSchema
Return Nothing
End Function
' <Node/> => ""
' <Node></Node> => ""
' <Node>Foo</Node> => "Foo"
' <Node><![CDATA[Foo]]></Node> => "Foo"
Public Sub ReadXml(reader As XmlReader) Implements IXmlSerializable.ReadXml
If reader.IsEmptyElement Then
Me.Value = ""
Else
reader.Read()
Select Case reader.NodeType
Case XmlNodeType.EndElement
Me.Value = "" ' empty after all...
Case XmlNodeType.Text, XmlNodeType.CDATA
Me.Value = reader.ReadContentAsString()
Case Else
Throw New InvalidOperationException("Expected text/cdata")
End Select
End If
End Sub
' "" => <Node/>
' "Foo" => <Node><![CDATA[Foo]]></Node>
Public Sub WriteXml(writer As XmlWriter) Implements IXmlSerializable.WriteXml
If Not String.IsNullOrEmpty(Me.Value) Then
writer.WriteCData(Me.Value)
End If
End Sub
Public Overrides Function ToString() As String
Return Me.Value
End Function
End Class
Above code is missing the fact that you must go past the content after you have read it. So this class as it stands won't work with a collection.
Change it to the following, and you can now hold Collections of CDataWrapper.
Value = reader.ReadContentAsString();
reader.Read();
Although this is an older post here are my 2¢. I addressed this issue by defining the data member as XmlElement.
[DataMember(Name = "MyCData")]
public XmlElement MyCDataField { get; set; }
