Feature Layer Count based on layer created from selection

[ChrisRobles]

Hi, 

Is it possible to get the current count of a feature layer without using the underlying feature class or having to iterate through a search and incrementing a counter? I have a layer that was created using a selection and I've tried getting the count of that layer but it only displays the count based on the underlying feature class.

[Wolf]

If you select all features in the newly created layer you can use GetSelection () and the selection count on the layer, otherwise you have to use a RowCursor on the FeatureLayer itself (not on the underlying FeatureClass or Table):

try
{
  // get all feature layers in the current map
  var map = MapView.Active.Map;
  if (map == null)
  {
    MessageBox.Show("No active map found.", "Error", System.Windows.MessageBoxButton.OK, System.Windows.MessageBoxImage.Error);
    return;
  }
  var featureLayers = map.GetLayersAsFlattenedList().OfType<FeatureLayer>().ToList();
  if (featureLayers.Count == 0)
  {
    MessageBox.Show("No feature layers found in the active map.", "Information", System.Windows.MessageBoxButton.OK, System.Windows.MessageBoxImage.Information);
    return;
  }
  // count rows in each feature layer
  StringBuilder result = new StringBuilder();
  await QueuedTask.Run(() =>
  {
    foreach (FeatureLayer layer in featureLayers)
    {
      // Get the row count for the feature layer
      // this is not working since it is getting the underlying table (which has all records in
      // the case where a layer is created with a 'select' clause
      // long rowCount = layer.GetTable().GetCount();

      // create a cursor for the layer (not the table)
      var rowCursor = layer.Search();
      long rowCount = 0;
      while (rowCursor.MoveNext())
      {
        rowCount++;
      }
      result.AppendLine($"{layer.Name}: {rowCount} rows");
    }
  });
  // Show the result in a message box
  MessageBox.Show(result.ToString(), "Row Count Results", System.Windows.MessageBoxButton.OK, System.Windows.MessageBoxImage.Information);
}
catch (Exception ex)
{
  MessageBox.Show($"An error occurred: {ex.Message}", "Error", System.Windows.MessageBoxButton.OK, System.Windows.MessageBoxImage.Error);
}

[ChrisRobles]

Thank you for the reply Wolf, is there any way you would suggest doing the count on a layer that has thousands or tens of thousands of features? I think having to select all features or iterating through each row would cause delay.

[Wolf · Accepted solution]

I don't see another way, however, i think processing will be fast since the layer data is cached in memory.  Here is my sample:

3141 records in 0.017 seconds.  

These are the code changes to measure the timing:

// count rows in each feature layer
StringBuilder result = new StringBuilder();
await QueuedTask.Run(() =>
{
  foreach (FeatureLayer layer in featureLayers)
  {
    // Get the row count for the feature layer
    // this is not working since it is getting the underlying table (which has all records in
    // the case where a layer is created with a 'select' clause
    // long rowCount = layer.GetTable().GetCount();

    // create a cursor for the layer (not the table)
    var rowCursor = layer.Search();
    long rowCount = 0;
    var timer = new Stopwatch();
    timer.Start(); 
    while (rowCursor.MoveNext())
    {
      rowCount++;
    }
    timer.Stop();
    var elapsedTime = timer.Elapsed;
    result.AppendLine($"{layer.Name}: {rowCount} rows  {elapsedTime:m\\:ss\\.fff} min.");
  }
});
// Show the result in a message box
MessageBox.Show(result.ToString(), "Row Count Results", System.Windows.MessageBoxButton.OK, System.Windows.MessageBoxImage.Information);

[ChrisRobles]

That worked great thank you!