public void SetShapeType( 
   GeometryType shapeType
)

public async Task MultiGeometryQueryDescription()
{
  await ArcGIS.Desktop.Framework.Threading.Tasks.QueuedTask.Run(() =>
  {
    DatabaseConnectionProperties databaseConnectionProperties = new DatabaseConnectionProperties(EnterpriseDatabaseType.SQLServer)
    {
      AuthenticationMode = AuthenticationMode.DBMS,
      Instance = "instance",
      Database = "database",
      User = "user",
      Password = "password"
    };

    using (Database database = new Database(databaseConnectionProperties))
    {
      QueryDescription pointQueryDescription = database.GetQueryDescription("select Description, SHAPE, UniqueID from MULTIGEOMETRYTEST", "MultiGeometryPoint");
      pointQueryDescription.SetShapeType(GeometryType.Point);
      using (Table pointTable = database.OpenTable(pointQueryDescription))
      {
        //use pointTable
      }

      QueryDescription polygonQueryDescription = database.GetQueryDescription("select Description, SHAPE, UniqueID from MULTIGEOMETRYTEST", "MultiGeometryPolygon");
      polygonQueryDescription.SetShapeType(GeometryType.Polygon);
      using (Table polygonTable = database.OpenTable(polygonQueryDescription))
      {
        //use polygonTable
      }
    }
  });
}