Serialize a FeatureClass to XML in ESRI ArcGIS - arcgis

Question

How can I serialize an IFeatureClass object to XML?
There are some resources for using IXMLSerializer on other ArcObjects, but that won't work for IFeatureClass because it doesn't implement ISerializable.

Answer 1

I've actual found my own answer to this question. I'm posting this question and answer here for the benefit of others and for feedback/critique on my approach.
IFeatureClass cannot be serialized directly, but IRecordSet2 can be. So the first step is implementing a method to convert IFeatureClass to IRecordSet2:
private static IRecordSet2 ConvertToRecordset(IFeatureClass fc)
{
IRecordSet recSet = new RecordSetClass();
IRecordSetInit recSetInit = recSet as IRecordSetInit;
recSetInit.SetSourceTable(fc as ITable, null);
return (IRecordSet2) recSetInit;
}
Then it's easy to use IXMLSerializer to get XML:
public static XElement StoreAsXml(IFeatureClass fc)
{
// Can't serialize a feature class directly, so convert
// to recordset first.
IRecordSet2 recordset = ConvertToRecordset(fc);
IXMLSerializer xmlSer = new XMLSerializerClass();
string sXml = xmlSer.SaveToString(recordset, null, null);
return XElement.Parse(sXml);
}
However, when you convert to IRecordSet2, you lose the feature class name, so when writing to a file, I add an element to the XML to hold the feature class name:
public static void StoreToFile(IFeatureClass fc, string filePath)
{
XElement xdoc = StoreAsXml(fc);
XElement el = new XElement("FeatureClass", new XAttribute( "name", fc.AliasName ),
xdoc);
el.Save(filePath);
}
Now, just reverse the process to read the XML into a feature class. Remember that an element was added to store the feature class name:
public static IFeatureClass RetreiveFromFile(string filepath)
{
XElement xdoc = XElement.Load(filepath);
string sName = xdoc.FirstAttribute.Value;
XNode recordset = xdoc.FirstNode;
return RetreiveFromXml(recordset, sName);
}
Simple de-serialization using IXMLSerializer to get a IRecordSet2:
public static IFeatureClass RetreiveFromXml(XNode node, string sName)
{
IXMLSerializer xmlDeSer = new XMLSerializerClass();
IRecordSet2 recordset = (IRecordSet2)xmlDeSer.LoadFromString(node.ToString(), null, null);
return ConvertToFeatureClass(recordset, sName);
}
This was the tricky part. I'm open to suggestions on how to improve this ... covert the IRecordSet2 object into an IFeatureClass:
private static IFeatureClass ConvertToFeatureClass(IRecordSet2 rs, string sName)
{
IWorkspaceFactory pWSFact = new ShapefileWorkspaceFactory();
string sTempPath = Path.GetTempPath();
IFeatureWorkspace pFWS = (IFeatureWorkspace)pWSFact.OpenFromFile( sTempPath, 0);
// Will fail (COM E_FAIL) if the dataset already exists
DeleteExistingDataset(pFWS, sName);
IFeatureClass pFeatClass = null;
pFeatClass = pFWS.CreateFeatureClass(sName, rs.Fields, null, null, esriFeatureType.esriFTSimple,
"SHAPE", "");
// Copy incoming record set table to new feature class's table
ITable table = (ITable) pFeatClass;
table = rs.Table;
IFeatureClass result = table as IFeatureClass;
// It will probably work OK without this, but it makes the XML match more closely
IClassSchemaEdit3 schema = result as IClassSchemaEdit3;
schema.AlterAliasName(sName);
schema.AlterFieldAliasName("FID", "");
schema.AlterFieldModelName("FID", "");
schema.AlterFieldAliasName("Shape", "");
schema.AlterFieldModelName("Shape", "");
// If individual fields need to be edited, do something like this:
// int nFieldIndex = result.Fields.FindField("Shape");
// IFieldEdit2 field = (IFieldEdit2)result.Fields.get_Field(nFieldIndex);
// Cleanup
DeleteExistingDataset(pFWS, sName);
return table as IFeatureClass;
}
Finally, a utility method for deleting an existing dataset. This was copy/pasted from somewhere, but I can't remember the source.
public static void DeleteExistingDataset(IFeatureWorkspace pFWS, string sDatasetName)
{
IWorkspace pWS = (IWorkspace)pFWS;
IEnumDatasetName pEDSN = pWS.get_DatasetNames(esriDatasetType.esriDTFeatureClass);
bool bDatasetExists = false;
pEDSN.Reset();
IDatasetName pDSN = pEDSN.Next();
while (pDSN != null)
{
if (pDSN.Name == sDatasetName)
{
bDatasetExists = true;
break;
}
pDSN = pEDSN.Next();
}
if (bDatasetExists)
{
IFeatureClass pFC = pFWS.OpenFeatureClass(sDatasetName);
IDataset pDataset = (IDataset)pFC;
pDataset.Delete();
}
}