Question

I’m getting the following (intermittent) errors in my workflow tracking:

“An error occurred while
calling tracking participants causing
the instance to be aborted. See the
inner exception for more details.
InnerException Message: Type
‘System.Data.SqlClient.SqlException’
with data contract name
‘SqlException:http://schemas.datacontract.org/2004/07/System.Data.SqlClient’
is not expected. Consider using a
DataContractResolver or add any types
not known statically to the list of
known types – for example, by using
the KnownTypeAttribute attribute or by
adding them to the list of known types
passed to
DataContractSerializer.”

My custom tracking participant looks something like this:

            protected override void Track (TrackingRecord record, TimeSpan timeout)
            {

              StringWriter sw = null;
              if (record == null) throw new ArgumentNullException("record");
              if (timeout == null) throw new ArgumentNullException("timeout");
              StringBuilder sb = new StringBuilder();
              sw = new StringWriter(sb);

              using (XmlTextWriter writer = new XmlTextWriter(sw) { Formatting = Formatting.Indented })
              {
                  DataContractSerializer serializer = new DataContractSerializer(record.GetType());
                  serializer.WriteObject(writer, record);
                  writer.Flush();
                  writer.Close();
              }


              _logger.Log(sb.ToString());
            }

How do I go about resolving this?

Also, are there any other types that workflow might throw at me that I haven’t seen yet but need to handle in my tracking participant?

Answer 1

Found the solution here: http://blogs.msdn.com/b/youssefm/archive/2009/06/05/introducing-a-new-datacontractserializer-feature-the-datacontractresolver.aspx

Create a custom DCR:

public class SharedTypeResolver : DataContractResolver
{
    public override bool TryResolveType(Type dataContractType, Type declaredType, DataContractResolver knownTypeResolver, out XmlDictionaryString typeName, out XmlDictionaryString typeNamespace)
    {    
        if (!knownTypeResolver.TryResolveType(dataContractType, declaredType, null, out typeName, out typeNamespace))
        {
            XmlDictionary dictionary = new XmlDictionary();
            typeName = dictionary.Add(dataContractType.FullName);
            typeNamespace = dictionary.Add(dataContractType.Assembly.FullName);
        }
        return true;
    }


    public override Type ResolveName(string typeName, string typeNamespace, Type declaredType, DataContractResolver knownTypeResolver)
    {
        return knownTypeResolver.ResolveName(typeName, typeNamespace, declaredType, null) ?? Type.GetType(typeName + ", " + typeNamespace);
    }
}

Change DCS line in my code:

DataContractSerializer serializer = new DataContractSerializer(record.GetType(), null, Int32.MaxValue, false, false, null, new SharedTypeResolver()

Job done.