1. The methods should return Task instead of void. Otherwise exception are shallowed. Alternative you could encapsulate the whole content of the method in a try catch block.
2. Try to follow the DRY principle.

For example the line:

new List<ExpandoObject>(_dataPreparer.GetResults()).ToDataTable().AsDataView();

may be extracted to a method:

private static IList<ExpandoObject> GetData(DataPreparer dataPreparer) { ... }

3. It seems that the instance variables _dataPreparer, _activeDirectorySearcher class variables are set / used from different methods. That increases the comlexity of the program flow. I would try to avoid such 'global writable states'.

The view model seems to be used as universal container with high coupling. In the medium term, I would try to move the logic of each method to a single class that is independent of the view model.

1. The methods should return Task instead of void. Otherwise exception are shallowed. Alternative you could encapsulate the whole content of the method in a try catch block.

See also: Asynchrone return types - Void Return Type

2. Try to follow the DRY principle.

For example the line:

new List<ExpandoObject>(_dataPreparer.GetResults()).ToDataTable().AsDataView();

may be extracted to a method:

private static IList<ExpandoObject> GetData(DataPreparer dataPreparer) { ... }

3. It seems that the instance variables _dataPreparer, _activeDirectorySearcher class variables are set / used from different methods. That increases the comlexity of the program flow. I would try to avoid such 'global writable states'.

The view model seems to be used as universal container with high coupling. In the medium term, I would try to move the logic of each method to a single class that is independent of the view model.