public void SetDefaultValue( 
   object defaultValue,
   Nullable<int> subtypeCode
)

private void ModifyExistingField(SchemaBuilder schemaBuilder, TableDefinition tableDefinition, string fieldNameToBeModified = "PropertyAddress")
{
    Field field = tableDefinition.GetFields().FirstOrDefault(f => f.Name.Contains(fieldNameToBeModified));

    // Update field's alias name and length
    FieldDescription fieldDescription = new FieldDescription(field)
    {
        AliasName = "Physical Property Address",
        Length = 50
    };

    // Update the default value
    fieldDescription.SetDefaultValue("123 Main St");

    // Enqueue modify operation
    schemaBuilder.Modify(new TableDescription(tableDefinition), field.Name, fieldDescription);

    // Execute DDL
    schemaBuilder.Build();
}