Multithreading with ArcObjects

Question

I am getting some weird errors while trying to implement multithreading with ArcObjects. I am trying following things on per thread basis:

1) Open SDE Workspace
2) Open Feature class
3) Perform Icursor

Eventually, It fails with some errors like: "Memory could not be read or write" or "AccessViolationException".
Looks like there are some memory leaks (though I don't know exactly where).

For more details please refer to the code below:

foreach (string featureClassName in settings.FeatureClassNames) 
{ 
 Thread thread = new Thread(new ParameterizedThreadStart(ReadFeatureClass)); 
 thread.ApartmentState = ApartmentState.STA; 
 object[] parameters = CreateParameters(featureClassName); 
 thread.Start(parameters); 
} 
 private void ReadFeatureClass(object parameters) 
 { 
 Settings settings; 
 string featureClassName; 
 ExtractParameters(parameters as object[], out settings, out featureClassName); 
 IFeatureWorkspace featureWorkspace = OpenFeatureWorkspace(settings); 
 ITable featureClass = featureWorkspace.OpenTable(featureClassName); 
 Marshal.ReleaseComObject(featureClass); 
 Marshal.ReleaseComObject(featureWorkspace); 
 } 
 private IFeatureWorkspace OpenFeatureWorkspace(Settings settings) 
 { 
 IWorkspaceFactory workspaceFactory = new SdeWorkspaceFactory(); 
 IPropertySet connectionProperties = new PropertySet(); 
 connectionProperties.SetProperty("SERVER", settings.Server); 
 connectionProperties.SetProperty("INSTANCE", settings.Instance); 
 connectionProperties.SetProperty("USER", settings.User); 
 connectionProperties.SetProperty("PASSWORD", settings.Password); 
 connectionProperties.SetProperty("VERSION", settings.Version); 
 IFeatureWorkspace featureWorkspace = workspaceFactory.Open(connectionProperties, 0) as IFeatureWorkspace; 
 return featureWorkspace; 
 } 

• Petr Krebs: On which line does it fail?
• MathiasWestin: Have you read this in the documentation: help.arcgis.com/en/sdk/10.0/arcobjects_net/conceptualhelp/…
• Petr Krebs: Mathias: you can tell from the code he is following all the usual COM threading guidelines (at least from my point of view)
• Petr Krebs: ok, maybe I'd replace "new SdeWorkspaceFactory" with an Activator.CreateInstance<T> call (it's a singleton-per-thread), but I do not suspect this to be the problem. i've run your (modified) code with no issues really.. (tested against an in-house SDE instance)
• adhiman: I get random errors in code. Most often it gives AccessViolation exception at this line ITable featureClass = featureWorkspace.OpenTable(featureClassName); You said you ran my code successfully without any issue with your Database. Is there an issue with my DB then.? Any Suggestions?

Answer 1

As I look at it, without the benefit of what you're looking for with the ICursor, I don't know that you need to fire this off into a new thread. I've used SDE Connections like yours many times. Below is an example from my code base that is currently working (I have an issue when I attempt to CREATE a feature class against a FGDB, but my sde is connecting great)

 public IWorkspace OpenSDEWorkspace(String server, String instance, String database,
 String version, String user, String password)
 {
 try
 {
 //create and populate the property set.
 IPropertySet2 propertySet = new PropertySetClass();
 propertySet.SetProperty("SERVER", server);
 propertySet.SetProperty("INSTANCE", instance);
 propertySet.SetProperty("DATABASE", database);
 propertySet.SetProperty("USER", user);
 propertySet.SetProperty("PASSWORD", password);
 propertySet.SetProperty("VERSION", version);
 IWorkspaceFactory2 sdeWorkspaceFactory;
 sdeWorkspaceFactory = (IWorkspaceFactory2)new SdeWorkspaceFactoryClass();
 IWorkspace workspace = (IWorkspace)sdeWorkspaceFactory.Open(propertySet, 0);
 return workspace;
 }
 catch (Exception e)
 {
 throw new Exception(String.Format("arcSDEWorkspaceOpen: {0}", e.Message), e);
 }
 }
 public ArrayList GetDomainValues(String codedvaluedomain)
 {
 ArrayList arrayList = new ArrayList();
 IWorkspace ws = (IWorkspace)ArcMap.Editor.EditWorkspace;
 if(ws == null)
 {
 ws = OpenSDEWorkspace("ip", "5151", "database", "version", "user", "password");
 }
 IWorkspaceDomains domains = (IWorkspaceDomains)ws;
 object[] domainobject = null;
 IEnumDomain domainEnum = domains.Domains;
 IDomain domain = domainEnum.Next();
 String name = "";
 while (domain != null)
 {
 name = domain.Name;
 domain = domainEnum.Next();
 if (name.Equals(codedvaluedomain))
 { 
 break;
 }
 }
 ICodedValueDomain codeddomain = new CodedValueDomainClass();
 codeddomain = domains.get_DomainByName(name) as ICodedValueDomain;
 domainobject = new object[codeddomain.CodeCount];
 for (int a = 0; a < codeddomain.CodeCount; a++)
 {
 object domainvalue = codeddomain.get_Value(a);
 String domainvaluename = codeddomain.get_Name(a);
 arrayList.Add(domainvaluename);
 }
 return arrayList;
 }

give your code a run without the thread and let it all run on the main and let me know what happens.

Good luck

Luke