public AttributeIndexDescription( 
   string indexName,
   TableDescription tableDescription,
   IEnumerable<string> indexFieldNames
)

public void CreatingTableWithIndex(SchemaBuilder schemaBuilder)
{
  FieldDescription nameFieldDescription = FieldDescription.CreateStringField("Name", 50);
  FieldDescription addressFieldDescription = FieldDescription.CreateStringField("Address", 200);

  // Creating a feature class, 'Buildings' with two fields
  TableDescription tableDescription = new TableDescription("Buildings", new List<FieldDescription>() { nameFieldDescription, addressFieldDescription });

  // Enqueue DDL operation to create a table
  TableToken tableToken = schemaBuilder.Create(tableDescription);

  // Creating an attribute index named as 'Idx'
  AttributeIndexDescription attributeIndexDescription = new AttributeIndexDescription("Idx", new TableDescription(tableToken),
    new List<string> { nameFieldDescription.Name, addressFieldDescription.Name });

  // Enqueue DDL operation to create an attribute index
  schemaBuilder.Create(attributeIndexDescription);

  // Execute build indexes operation
  bool isBuildSuccess = schemaBuilder.Build();
}

public void AddingIndexes(SchemaBuilder schemaBuilder, FeatureClassDefinition featureClassDefinition)
{
  // Field names to add in the attribute index
  string fieldName = featureClassDefinition.GetFields().First(f => f.AliasName.Contains("Name")).Name;
  string fieldAddress = featureClassDefinition.GetFields().First(f => f.AliasName.Contains("Address")).Name;

  // Creating an attribute index with index name 'Idx' and two participating fields' name
  AttributeIndexDescription attributeIndexDescription = new AttributeIndexDescription("Idx", new TableDescription(featureClassDefinition), new List<string> { fieldName, fieldAddress });

  // Enqueue DDL operation for an attribute index creation 
  schemaBuilder.Create(attributeIndexDescription);

  // Creating the spatial index 
  SpatialIndexDescription spatialIndexDescription = new SpatialIndexDescription(new FeatureClassDescription(featureClassDefinition));

  // Enqueue DDL operation for the spatial index creation
  schemaBuilder.Create(spatialIndexDescription);

  // Execute build indexes operation
  bool isBuildSuccess = schemaBuilder.Build();

  if (!isBuildSuccess)
  {
    IReadOnlyList<string> errors = schemaBuilder.ErrorMessages;
    // Iterate and handle errors 
  }
}