public TinSurfaceType SurfaceType {get;}

{
  var dsCount = terrainDataset.GetDataSourceCount();
  IReadOnlyList<ArcGIS.Core.Data.Analyst3D.TerrainDataSource> dataSources = terrainDataset.GetDataSources();
  foreach (var ds in dataSources)
  {
    var dsName = ds.DataSourceName;
    var surfaceType = ds.SurfaceType;
    var maxResolution = ds.MaximumResolution;
    var minResolution = ds.MinimumResolution;
  }
}