public sealed class AttributeIndexDescription : IndexDescription 

{
  await QueuedTask.Run(() =>
  {
    using (var kg = GetKnowledgeGraph(url))
    {
      var entity_name = "PhoneCall";

      //indexes are managed on the GDB objects...
      var entity_table_def = kg.GetDefinition<TableDefinition>(entity_name);
      var entity_table_desc = new TableDescription(entity_table_def);

      var entity_table_flds = entity_table_def.GetFields();
      AttributeIndexDescription attr_index1 = null;
      AttributeIndexDescription attr_index2 = null;
      foreach (var fld in entity_table_flds)
      {
        //index the first string field
        if (fld.FieldType == FieldType.String && attr_index1 == null)
        {
          if (fld.Name == "ESRI__ID")//special case
            continue;
          //Index _must_ be ascending for KG
          attr_index1 = new AttributeIndexDescription(
            "Index1", entity_table_desc, new List<string> { fld.Name })
          {
            IsAscending = true
          };
        }
        //index the first numeric field (if there is one)
        if ((fld.FieldType == FieldType.BigInteger ||
             fld.FieldType == FieldType.Integer ||
             fld.FieldType == FieldType.Single ||
             fld.FieldType == FieldType.SmallInteger ||
             fld.FieldType == FieldType.Double) && attr_index2 == null)
        {
          attr_index2 = new AttributeIndexDescription(
            "Index2", entity_table_desc, new List<string> { fld.Name })
          {
            IsAscending = true,
            IsUnique = true //optional - unique if all values are to be unique in the index
          };
        }
        if (attr_index1 != null && attr_index2 != null) break;
      }

      if (attr_index1 == null && attr_index2 == null)
        return; //nothing to index

      //Run the schema builder
      try
      {
        SchemaBuilder sb = new(kg);
        if (attr_index1 != null)
          sb.Create(attr_index1);
        if (attr_index2 != null)
          sb.Create(attr_index2);
        if (!kg.ApplySchemaEdits(sb))
        {
          var err_msg = string.Join(",", sb.ErrorMessages.ToArray());
          System.Diagnostics.Debug.WriteLine($"Create index error: {err_msg}");
        }
      }
      catch (Exception ex)
      {
        System.Diagnostics.Debug.WriteLine(ex.ToString());
      }
    }
  });
}

{
  await QueuedTask.Run(() =>
  {
    using (var kg = GetKnowledgeGraph(url))
    {
      var entity_name = "PhoneCall";

      //indexes are managed on the GDB objects...
      var entity_table_def = kg.GetDefinition<TableDefinition>(entity_name);
      var entity_table_desc = new TableDescription(entity_table_def);

      var indexes = entity_table_def.GetIndexes();
      foreach (var idx in indexes)
      {
        System.Diagnostics.Debug.WriteLine($"Index {idx.GetName()}");
      }
      var idx1 = indexes.FirstOrDefault(
        idx => idx.GetName().ToLower() == "Index1".ToLower());
      var idx2 = indexes.FirstOrDefault(
        idx => idx.GetName().ToLower() == "Index2".ToLower());

      if (idx1 == null && idx2 == null)
        return;

      //Run the schema builder
      try
      {
        SchemaBuilder sb = new(kg);

        if (idx1 != null)
        {
          var idx_attr = new AttributeIndexDescription(idx1, entity_table_desc);
          sb.Delete(idx_attr);
        }
        if (idx2 != null)
        {
          var idx_attr = new AttributeIndexDescription(idx2, entity_table_desc);
          sb.Delete(idx_attr);
        }

        if (!kg.ApplySchemaEdits(sb))
        {
          var err_msg = string.Join(",", sb.ErrorMessages.ToArray());
          System.Diagnostics.Debug.WriteLine($"Delete index error: {err_msg}");
        }
      }
      catch (Exception ex)
      {
        System.Diagnostics.Debug.WriteLine(ex.ToString());
      }
    }
  });
}