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In a custom layer I have a workspace variable (File GDB or SDE) that I need to persist (save/load).

Therefore I need to persist the ConnectionProperties of the workspace. Thankfully ConnectionProperties returns a PropertySet which implements IPersistStream so persisting this is trivial. But I also need to persist the type of workspace factory to use.

Unfortunately WorkspaceFactory does not implement IPersistStream so persisting it directly does not work (returns null when reading).

Is there a way to do this?

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    I think it's pretty safe to use the string comparison in your first example. Since they are esri constants they should never change. – Rich Wawrzonek Aug 20 '15 at 23:11
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The asker found a way to do this:

Persist the WorkspaceFactory.WorkspaceType of the workspace. Then I get the workspace factory with this method:

public static IWorkspaceFactory workspaceFactory(esriWorkspaceType type)
{
    string stype;
    if (type == esriWorkspaceType.esriLocalDatabaseWorkspace)
        stype = "esriDataSourcesGDB.FileGDBWorkspaceFactory";
    else if (type == esriWorkspaceType.esriRemoteDatabaseWorkspace)
         stype = "esriDataSourcesGDB.SdeWorkspaceFactory";
    else
         return null;

    Type factoryType = Type.GetTypeFromProgID(stype);
    IWorkspaceFactory wsf = (IWorkspaceFactory)Activator.CreateInstance(factoryType);
    return wsf;
}

I don't think this is good coding practice though using hardcoded strings. I would not have known these strings if I had not found them in code samples from ESRI.

Is there a better way to do this?

I tried using the Type:

UID uid = workspace.WorkspaceFactory.GetClassID();
Guid guid = new Guid(uid.Value as string);
Type workspaceFactoryType = Type.GetTypeFromCLSID(guid); 

This seemed more appealing since it would avoid hardcoded strings:

IWorkspaceFactory wf = Activator.CreateInstance(workspaceFactoryType) as IWorkspaceFactory;

The only problem is that I could not persist Type.

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