public sealed class DatastoreConfiguration 

{
  // ApplicationOptions.EditingOptions.EnableEditingFromEditTab is true
  // ApplicationOptions.EditingOptions.IsSingleWorkspaceEditSession is true

  Geodatabase egdb = new Geodatabase(new DatabaseConnectionFile(new Uri("path\\to\\sde\\file\\sdefile.sde")));

  // setup the configuration to edit the data registered as versioned in the egdb
  var datastoreConfig = new DatastoreConfiguration(egdb, VersionState.Versioned);

  // start the edit session on the workspace
  var project = Project.Current;
  var v_success = await project.SetSingleEditWorkspaceAsync(datastoreConfig);

  // OR 

  // setup the configuration to edit the data that is not registered as versioned
  var nonVersionedDatastoreConfig = new DatastoreConfiguration(egdb, VersionState.NonVersioned);
  // start the edit session on the workspace
  var nv_success = await project.SetSingleEditWorkspaceAsync(nonVersionedDatastoreConfig);
}