public ShapeDescription ShapeDescription {get;}

public void AddFieldWithDomainSnippet(Geodatabase geodatabase)
{
  // Adding a field,'PipeType', which uses the coded value domain to the 'Pipes' FeatureClass

  //The FeatureClass to add field
  string featureClassName = "Pipes";

  SchemaBuilder schemaBuilder = new SchemaBuilder(geodatabase);

  // Create a CodedValueDomain description for water pipes
  CodedValueDomainDescription pipeDomainDescription =
    new CodedValueDomainDescription("WaterPipeTypes", FieldType.String,
    new SortedList<object, string> { { "C_1", "Copper" },
      { "S_2", "Steel" } })
    {
      SplitPolicy = SplitPolicy.Duplicate,
      MergePolicy = MergePolicy.DefaultValue
    };

  // Create a coded value domain token
  CodedValueDomainToken codedValueDomainToken = schemaBuilder.Create(pipeDomainDescription);

  // Create a new description from domain token
  CodedValueDomainDescription codedValueDomainDescription = new CodedValueDomainDescription(codedValueDomainToken);

  // Create a field named as 'PipeType' using a domain description
  FieldDescription domainFieldDescription = new FieldDescription("PipeType", FieldType.String)
  { DomainDescription = codedValueDomainDescription };

  //Retrieve existing information for 'Pipes' FeatureClass
  FeatureClassDefinition originalFeatureClassDefinition = geodatabase.GetDefinition<FeatureClassDefinition>(featureClassName);
  FeatureClassDescription originalFeatureClassDescription =
    new FeatureClassDescription(originalFeatureClassDefinition);

  // Add domain field on existing fields
  List<FieldDescription> modifiedFieldDescriptions = new List<FieldDescription>(originalFeatureClassDescription.FieldDescriptions) { domainFieldDescription };

  // Create a new description with updated fields for 'Pipes' FeatureClass 
  FeatureClassDescription featureClassDescription =
    new FeatureClassDescription(originalFeatureClassDescription.Name, modifiedFieldDescriptions,
                                   originalFeatureClassDescription.ShapeDescription);

  // Update the 'Pipes' FeatureClass with domain field
  schemaBuilder.Modify(featureClassDescription);

  // Build status
  bool buildStatus = schemaBuilder.Build();

  // Build errors
  if (!buildStatus)
  {
    IReadOnlyList<string> errors = schemaBuilder.ErrorMessages;
  }
}