DateSample.cs

// Copyright 2021 Google Inc. All Rights Reserved.
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
//     http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

using Google.Cloud.EntityFrameworkCore.Spanner.Samples.SampleModel;
using Google.Cloud.EntityFrameworkCore.Spanner.Storage;
using Microsoft.EntityFrameworkCore;
using System;
using System.Linq;
using System.Threading.Tasks;

/// <summary>
/// The Clr type <see cref="DateTime"/> is often used for both dates and timestamps. Cloud Spanner has two distinct
/// data types for DATE and TIMESTAMP. To distinguish between the two in Entity Framework Core, it is recommended to
/// use <see cref="SpannerDate"/> to map DATE columns and <see cref="DateTime"/> to map TIMESTAMP columns.
/// 
/// Run from the command line with `dotnet run DateSample`
/// </summary>
public static class DateSample
{
    public static async Task Run(string connectionString)
    {
        using var context = new SpannerSampleDbContext(connectionString);
        var singer = new Singer
        {
            SingerId = Guid.NewGuid(),
            FirstName = "Yvette",
            LastName = "Wendelson",
            // SpannerDate is specifically designed to map a DATE column in a Cloud Spanner
            // database to a property of an entity. DateTime properties will by default be
            // mapped to TIMESTAMP columns.
            BirthDate = new SpannerDate(1980, 10, 17),
        };
        await context.Singers.AddAsync(singer);
        await context.SaveChangesAsync();

        // Commonly used properties and methods of SpannerDate are mapped to the equivalent Cloud Spanner functions.
        var singersBornIn1980 = await context.Singers
            .Where(s => s.BirthDate.GetValueOrDefault().Year == 1980)
            .OrderBy(s => singer.LastName)
            .ToListAsync();
        foreach (var s in singersBornIn1980)
        {
            Console.WriteLine($"Born in 1980: {s.FullName} ({s.BirthDate})");
        }
    }
}