public MergePolicy MergePolicy {get; set;}

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

    SchemaBuilder schemaBuilder = new SchemaBuilder(geodatabase);

    // Create a coded value domain 
    CodedValueDomainToken codedValueDomainToken = schemaBuilder.Create(codedValueDomainDescription);
    schemaBuilder.Build();
}