public static FieldDescription CreateObjectIDField()

// Create a PoleInspection table with the following fields
//  GlobalID
//  ObjectID
//  InspectionDate (date)
//  InspectionResults (pre-existing InspectionResults coded value domain)
//  InspectionNotes (string)

// This static helper routine creates a FieldDescription for a GlobalID field with default values
FieldDescription globalIDFieldDescription = FieldDescription.CreateGlobalIDField();

// This static helper routine creates a FieldDescription for an ObjectID field with default values
FieldDescription objectIDFieldDescription = FieldDescription.CreateObjectIDField();

// Create a FieldDescription for the InspectionDate field
FieldDescription inspectionDateFieldDescription = new FieldDescription("InspectionDate", FieldType.Date)
{
  AliasName = "Inspection Date"
};

// This static helper routine creates a FieldDescription for a Domain field (from a pre-existing domain)
FieldDescription inspectionResultsFieldDescription = FieldDescription.CreateDomainField("InspectionResults", new CodedValueDomainDescription(inspectionResultsDomain));
inspectionResultsFieldDescription.AliasName = "Inspection Results";

// This static helper routine creates a FieldDescription for a string field
FieldDescription inspectionNotesFieldDescription = FieldDescription.CreateStringField("InspectionNotes", 512);
inspectionNotesFieldDescription.AliasName = "Inspection Notes";

// Assemble a list of all of our field descriptions
List<FieldDescription> fieldDescriptions = new List<FieldDescription>()
  { globalIDFieldDescription, objectIDFieldDescription, inspectionDateFieldDescription, inspectionResultsFieldDescription, inspectionNotesFieldDescription };

// Create a TableDescription object to describe the table to create
TableDescription tableDescription = new TableDescription("PoleInspection", fieldDescriptions);

// Create a SchemaBuilder object
SchemaBuilder schemaBuilder = new SchemaBuilder(geodatabase);

// Add the creation of PoleInspection to our list of DDL tasks
schemaBuilder.Create(tableDescription);

// Execute the DDL
bool success = schemaBuilder.Build();

// Inspect error messages
if (!success)
{
  IReadOnlyList<string> errorMessages = schemaBuilder.ErrorMessages;
  //etc.
}

// Create a Cities feature class with the following fields
//  GlobalID
//  ObjectID
//  Name (string)
//  Population (integer)

// This static helper routine creates a FieldDescription for a GlobalID field with default values
FieldDescription globalIDFieldDescription = FieldDescription.CreateGlobalIDField();

// This static helper routine creates a FieldDescription for an ObjectID field with default values
FieldDescription objectIDFieldDescription = FieldDescription.CreateObjectIDField();

// This static helper routine creates a FieldDescription for a string field
FieldDescription nameFieldDescription = FieldDescription.CreateStringField("Name", 255);

// This static helper routine creates a FieldDescription for an integer field
FieldDescription populationFieldDescription = FieldDescription.CreateIntegerField("Population");

// Assemble a list of all of our field descriptions
List<FieldDescription> fieldDescriptions = new List<FieldDescription>()
  { globalIDFieldDescription, objectIDFieldDescription, nameFieldDescription, populationFieldDescription };

// Create a ShapeDescription object
ShapeDescription shapeDescription = new ShapeDescription(GeometryType.Point, spatialReference);

// Alternatively, ShapeDescriptions can be created from another feature class.  In this case, the new feature class will inherit the same shape properties of the existing class
ShapeDescription alternativeShapeDescription = new ShapeDescription(existingFeatureClass.GetDefinition());

// Create a FeatureClassDescription object to describe the feature class to create
FeatureClassDescription featureClassDescription = 
  new FeatureClassDescription("Cities", fieldDescriptions, shapeDescription);

// Create a SchemaBuilder object
SchemaBuilder schemaBuilder = new SchemaBuilder(geodatabase);

// Add the creation of the Cities feature class to our list of DDL tasks
schemaBuilder.Create(featureClassDescription);

// Execute the DDL
bool success = schemaBuilder.Build();

// Inspect error messages
if (!success)
{
  IReadOnlyList<string> errorMessages = schemaBuilder.ErrorMessages;
  //etc.
}