[Mono-dev] [PATCH] Fix serialization of typed datasets

[John Lenz]

This patch allows typed datasets produced by Microsoft's xsd.exe to work
correctly in mono.  With this patch, I can serialize or deserialize the
classes in the mono runtime and even communicate over
the network where for example the client is running on mono and the
server is running on MS.NET.

I have only tested the XML serialization, I have not tested the binary
serialization.  Thus my patch makes no changes to the code paths
for binary serialization, but I suspect it actually fixes bug #427769
because of the added call to InitializeDerivedDataSet in the constructor.

Since these functions are undocumented, here is how I found out how they
should work:  I looked at the code produced by xsd.exe and mono's
implementation of the DataSet class.  Several things did not make sense
until I made the changes below.  All are really obvious if you see what
the xsd.exe produced code is expecting.

I also ran a test server on the MS.NET runtime and a test client in
monodevelop on the mono runtime.  I stuck some breakpoints into the
client using monodevelop to see what the serialization format looked like.

Here are the changes:

1) The GetSerializationData() function should only load the data, not
the schema.  This function is called by the derived dataset constructor
after it has loaded the schema.  So I moved the schema loading code out
of GetSerializationData and into the constructor.

2) We need to know the incoming serialization mode (Included or Excluded).
This is serialized in the "SchemaSerializationMode.DataSet", which I found
using monodevelop to debug the client constructor.  Fix the
DetermineSchemaSerializationMode function and add the parameter to the
serialization code.

3) Implement the DataSet(SerializationInfo, StreamingContext, bool)
constructor.  Basically, if the schema is excluded we call
InitializeDerivedDataSet to create it.  This is really weird and
I have no idea why the derived class does not call it directly.
But the xsd.exe generated code expects it is called from the
constructor.  The InitializeDerivedDataSet
function in the base class should do nothing, it is overridden in each
typed dataset.

Index: class/System.Data/System.Data/DataSet.cs
===================================================================
--- class/System.Data/System.Data/DataSet.cs	(revision 141910)
+++ class/System.Data/System.Data/DataSet.cs	(working copy)
@@ -95,6 +95,17 @@
  		protected DataSet (SerializationInfo info, StreamingContext context)
  			: this ()
  		{
+#if NET_2_0
+			if (IsBinarySerialized (info, context)) {
+				BinaryDeserialize (info);
+				return;
+			}
+#endif
+			string s = info.GetValue ("XmlSchema", typeof (String)) as String;
+			XmlTextReader reader = new XmlTextReader (new StringReader (s));
+			ReadXmlSchema (reader);
+			reader.Close ();
+
  			GetSerializationData (info, context);
  		}

@@ -1132,6 +1143,9 @@
  		{
  #if NET_2_0
  			if (RemotingFormat == SerializationFormat.Xml) {
+
+				info.AddValue ("SchemaSerializationMode.DataSet", this.SchemaSerializationMode);
+
  #endif
  				StringWriter sw = new StringWriter ();
  				XmlTextWriter writer = new XmlTextWriter (sw);
@@ -1155,19 +1169,8 @@
  		#region Protected Methods
  		protected void GetSerializationData (SerializationInfo info, StreamingContext context)
  		{
-#if NET_2_0
-			if (IsBinarySerialized (info, context)) {
-				BinaryDeserialize (info);
-				return;
-			}
-#endif
-			string s = info.GetValue ("XmlSchema", typeof (String)) as String;
+			string s = info.GetValue ("XmlDiffGram", typeof (String)) as String;
  			XmlTextReader reader = new XmlTextReader (new StringReader (s));
-			ReadXmlSchema (reader);
-			reader.Close ();
-
-			s = info.GetValue ("XmlDiffGram", typeof (String)) as String;
-			reader = new XmlTextReader (new StringReader (s));
  			ReadXml (reader, XmlReadMode.DiffGram);
  			reader.Close ();
  		}
@@ -1547,10 +1550,26 @@
  		private bool dataSetInitialized = true;
  		public event EventHandler Initialized;

-		[MonoTODO]
  		protected DataSet (SerializationInfo info, StreamingContext context, bool constructSchema)
-			: this (info, context)
+			: this ()
  		{
+			if (DetermineSchemaSerializationMode (info, context) == SchemaSerializationMode.ExcludeSchema) {
+				InitializeDerivedDataSet ();
+			}
+
+			if (IsBinarySerialized (info, context)) {
+				BinaryDeserialize (info);
+				return;
+			}
+
+			if (constructSchema) {
+				string s = info.GetValue ("XmlSchema", typeof (String)) as String;
+				XmlTextReader reader = new XmlTextReader (new StringReader (s));
+				ReadXmlSchema (reader);
+				reader.Close ();
+
+				GetSerializationData (info, context);
+			}
  		}

  		SerializationFormat remotingFormat = SerializationFormat.Xml;
@@ -1751,10 +1770,8 @@
  			OnDataSetInitialized (e);
  		}

-		[MonoTODO]
  		protected virtual void InitializeDerivedDataSet ()
  		{
-			throw new NotImplementedException ();
  		}

  		protected SchemaSerializationMode DetermineSchemaSerializationMode (XmlReader reader)
@@ -1764,6 +1781,13 @@

  		protected SchemaSerializationMode DetermineSchemaSerializationMode (SerializationInfo info, StreamingContext context)
  		{
+			SerializationInfoEnumerator e = info.GetEnumerator ();
+			while (e.MoveNext ()) {
+				if (e.Name == "SchemaSerializationMode.DataSet") {
+					return (SchemaSerializationMode) e.Value;
+				}
+			}
+
  			return SchemaSerializationMode.IncludeSchema;
  		}