使用Blazor构建CRUD项目
在小公司中,往往没有一个前后端分离的大型团队,去各司其职的负责构建web应用程序。面对比较简单的需求,可能所谓团队只有一个人,既要开发前端又要开发后端。如果能有一项技术,能够前后端通吃,并且具备非常高的开发效率,那就非常适合小公司的小型项目的小型甚至一人团队来使用了。
aspdotnet就是这样高效的后端开发框架,而有了blazor后,C#前端也可以通吃了,真正做到了一套框架,一种语言,前后端通吃。
本文使用aspdotnet + blazor,快速构建了一个CRUD项目。
1. 新建项目
新的Blazor Web App,可以同时使用Blazor Server和Blazor WebAssembly两种渲染模式
勾上sample pages
在生成的解决方案中,有两个项目
后面.Client的,就是WebAssembly的部分,这一部分只需要关注Pages里的页面。当用户访问这个页面时,就是WebAssembly,于是就可以离线操作页面。
如果页面功能不涉及前后台数据交互,则可以使用WebAssembly模式。
例如,问卷调查、考试,从后台获取数据,前提渲染出题目后,就是答题的过程。知道用户提交答案之前,都不需要与后台又交互。这时候整个作答页面可以使用WebAssembly。
2. 添加数据库支持
给项目添加sqlite数据库支持
[*]引入nuget包
[*]编写DbContext类
[*]编写Model类
[*]运行Package Manager Console命令
新建DefaultDbContext.cs文件
using Microsoft.EntityFrameworkCore;
using QuickCRUD.Models;
namespace QuickCRUD;
public class DefaultDbContext : DbContext
{
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseSqlite("Data Source=quick_crud.sqlite");
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.ApplyConfigurationsFromAssembly(GetType().Assembly);
}
public DbSet<WeatherForecast> WeatherForecasts { get; set; }
}新建WeatherForecast.cs文件。里面除了模型类,还有一个Configuration类,用来模型与配置数据库中表和表字段的对应关系。
删除自动生成的实例代码里,Pages/Weather.razor中的相关内容。
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Metadata.Builders;
namespace QuickCRUD.Models;
public class WeatherForecast
{
public int Id { get; set; }
public DateOnly Date { get; set; }
public int TemperatureC { get; set; }
public string? Summary { get; set; }
public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
}
public class WeatherForecastConfig : IEntityTypeConfiguration<WeatherForecast>
{
public void Configure(EntityTypeBuilder<WeatherForecast> builder)
{
builder.ToTable("weather_forcast");
builder.Property("Id").HasColumnName("obj_id").ValueGeneratedOnAdd();
builder.Property("Date").HasColumnName("ddate").HasColumnType("Text");
builder.Property("TemperatureC").HasColumnName("temp_c");
builder.Property("Summary").HasColumnName("summary");
}
}Package Manger Console,运行命令
Add-Migration Init
Update-Database此时,将自动生成数据库与表结构
3. 编写Repo代码
Repo是直接与数据库打交道的代码,提供了基本的对数据库表的CRUD操作
为了操作数据库,注入了DbContext类
新建WeatherForecastRepo.cs文件,里面利用DbContext对象,编写增删改查数据库的基本操作方法:
using Microsoft.EntityFrameworkCore;
using QuickCRUD.Models;
namespace QuickCRUD.Repos;
public class WeatherForecastRepo
{
private readonly DefaultDbContext _context;
public WeatherForecastRepo(DefaultDbContext context)
{
_context = context;
}
public async Task<int> Add(WeatherForecast entity)
{
_context.WeatherForecasts.Add(entity);
return await _context.SaveChangesAsync();
}
public async Task<int> DeleteAll()
{
_context.WeatherForecasts.RemoveRange(
_context.WeatherForecasts.Take(_context.WeatherForecasts.Count())
);
return await _context.SaveChangesAsync();
}
public async Task<int> DeleteById(int id)
{
var w = await GetById(id);
if (w != null)
{
_context.WeatherForecasts.Remove(w);
}
return await _context.SaveChangesAsync();
}
public async Task<List<WeatherForecast>?> GetAll()
{
return await _context.WeatherForecasts.ToListAsync();
}
public async Task<WeatherForecast?> GetById(int id)
{
return await _context.WeatherForecasts.FindAsync(id);
}
public async Task<int> Update(WeatherForecast entity)
{
var w = await GetById(entity.Id);
if (w != null)
{
_context.WeatherForecasts.Update(entity);
}
return await _context.SaveChangesAsync();
}
} 4. 编写前端list代码
[*]引入QuickGrid包
[*]编写前端list展示页面的component
[*]编写add页面component
[*]根据需要编写service文件
编写展示数据的list页面,在Pages文件夹下建立Weather.razor文件
@page "/weather"
@rendermode InteractiveServer
@inject WeatherForecastService weatherForecastService
@inject NavigationManager nav
<PageTitle>Weather</PageTitle>
<h1>Weather</h1>
<button class="btn btn-sm btn-outline-success" @onclick="BtnNew">New</button>
<button class="btn btn-sm btn-danger" @onclick="BtnDeleteAll">Delete All</button>
<button class="btn btn-sm btn-outline-info" @onclick="BtnGenerateRandomDate">Generate Random Date</button>
@if (forecasts == null)
{
<p><em>Loading...</em></p>
}
else
{
<QuickGrid class="table" Items="forecasts.AsQueryable()">
<PropertyColumn Property="@(f=>f.Id)" />
<PropertyColumn Property="@(f=>f.Date)" />
<PropertyColumn Title="Temp.(C)" Property="@(f=>f.TemperatureC)" />
<PropertyColumn Title="Temp.(F)" Property="@(f=>f.TemperatureF)" />
<PropertyColumn Property="@(f=>f.Summary)" />
<TemplateColumn Context="f">
<button class="btn btn-sm btn-outline-info" @onclick="_=>BtnEdit(f.Id)">Edit</button>
<button class="btn btn-sm btn-outline-danger" @onclick="_=>BtnDelete(f.Id)">Delete</button>
</TemplateColumn>
</QuickGrid>
}
@code {
private List<WeatherForecast>? forecasts;
protected override async Task OnInitializedAsync()
{
forecasts = await weatherForecastService.AllForecast();
}
private void BtnNew()
{
nav.NavigateTo("/weather/add", true, true);
}
private void BtnEdit(int id)
{
nav.NavigateTo($"/weather/edit/{id}", true, true);
}
private async Task BtnDelete(int id)
{
await weatherForecastService.DeleteForecast(id);
nav.Refresh(true);
}
private async Task BtnDeleteAll()
{
await weatherForecastService.DeleteAllForecast();
nav.Refresh(true);
}
private async Task BtnGenerateRandomDate()
{
await weatherForecastService.GenerateRandom();
nav.Refresh(true);
}
}注入了WeatherForecastService
需要注意页面上方的@rendermode InteractiveServer,这个标注将使得页面在服务端进行渲染,这是必不可少的,因为我们使用的是service,里面注入了repo,而repo中使用的是EF,这就意味着service的代码必须在服务端运行,所以这个页面必须在服务端渲染完毕后,再在前端展示。如果我们的service选择使用HttpClient获取后端api接口数据,则可以使用Wasm模式,就像Count.razor页面。
5. 编写Service
前端页面当需要使用数据时,将注入service,service如果需要向数据库请求数据,则在service中注入repo
编写WeatherForecastService.cs文件
using QuickCRUD.Models;
using QuickCRUD.Repos;
namespace QuickCRUD.Services;
public class WeatherForecastService
{
private readonly WeatherForecastRepo _repo;
public WeatherForecastService(WeatherForecastRepo repo)
{
_repo = repo;
}
public async Task<WeatherForecast> GetById(int id)
{
var f = await _repo.GetById(id);
if (f == null) return new();
return f;
}
public async Task<List<WeatherForecast>> AllForecast()
{
var result = await _repo.GetAll();
if (result == null)
{
return [];
}
else
{
return result;
}
}
public async Task<int> NewForecast(WeatherForecast forecast)
{
if (forecast == null) return 0;
return await _repo.Add(forecast);
}
public async Task<int> UpdateForecast(WeatherForecast forecast)
{
if (forecast == null) { return 0; }
return await _repo.Update(forecast);
}
public async Task<int> DeleteForecast(int id)
{
return await _repo.DeleteById(id);
}
public async Task<int> DeleteAllForecast()
{
return await _repo.DeleteAll();
}
public async Task<int> GenerateRandom()
{
var startDate = DateOnly.FromDateTime(DateTime.Now);
var summaries = new[] { "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching" };
var forecasts = Enumerable.Range(1, 10).Select(index => new WeatherForecast
{
Date = startDate.AddDays(index),
TemperatureC = Random.Shared.Next(-20, 55),
Summary = summaries
}).ToList();
foreach (var forecast in forecasts) await _repo.Add(forecast);
return forecasts.Count;
}
}6. 编写add和edit子页面
新建WeatherAdd.razor文件
@page "/weather/add"
@rendermode InteractiveServer
@inject WeatherForecastService weatherForecastService
@inject NavigationManager nav
<h1>New Weather Forecast</h1>
<EditForm Model="forecast" OnValidSubmit="SubmitForecast">
<p>
<label>
Date:
<InputDate @bind-Value="forecast.Date" />
</label>
</p>
<p>
<label>
Temperature C:
<InputNumber @bind-Value="forecast.TemperatureC" />
</label>
</p>
<p>
<label>
Summary:
<InputText @bind-Value="forecast.Summary" />
</label>
</p>
<p>
<button type="submit" class="btn btn-primary">Submit</button>
</p>
</EditForm>
<button class="btn btn-outline-primary" @onclick="BtnCancel">Cancel</button>
@code {
private WeatherForecast forecast { get; set; } = new() { Date = DateOnly.FromDateTime(DateTime.Today) };
private async Task SubmitForecast()
{
await weatherForecastService.NewForecast(forecast);
nav.NavigateTo("/weather", true, true);
}
private void BtnCancel()
{
nav.NavigateTo("/weather", true, true);
}
}新建WeatherEdit.razor文件
@page "/weather/edit/{id:int}"
@rendermode InteractiveServer
@inject WeatherForecastService weatherForecastService
@inject NavigationManager nav
<h1>Edit Weather Forecast</h1>
<h3>Id: @Id</h3>
<EditForm Model="forecast" OnValidSubmit="SubmitForecast">
<p>
<label>
Date:
<InputDate @bind-Value="forecast.Date" />
</label>
</p>
<p>
<label>
Temperature C:
<InputNumber @bind-Value="forecast.TemperatureC" />
</label>
</p>
<p>
<label>
Summary:
<InputText @bind-Value="forecast.Summary" />
</label>
</p>
<p>
<button type="submit" class="btn btn-primary">Submit</button>
</p>
</EditForm>
<button class="btn btn-outline-primary" @onclick="BtnCancel">Cancel</button>
@code {
public int Id { get; set; }
private WeatherForecast forecast { get; set; } = new();
protected override async Task OnParametersSetAsync()
{
forecast = await weatherForecastService.GetById(Id);
}
private void BtnCancel()
{
nav.NavigateTo("/weather", true, true);
}
private async Task SubmitForecast()
{
await weatherForecastService.UpdateForecast(forecast);
nav.NavigateTo("/weather", true, true);
}
}edit页面与add页面的不同在于,需要传入id参数
7. 检查依赖注入
检查一下Program.cs文件中,是否将dbcontext,repo和service都配置了依赖注入
builder.Services.AddDbContext<DefaultDbContext>();
builder.Services.AddScoped<WeatherForecastRepo>();
builder.Services.AddScoped<WeatherForecastService>();8. 效果展示
9. 发布
[*]将sqlite数据库的文件编译属性调整为复制到输出目录
[*]publish参数
最终生成
至此,最简单的CRUD完成了
10. 利用泛型的Repo
目前的Repo需要逐个编写操作数据库的方法,如果新增了一个model,则需要对应添加一个repo类,并再次重新编写所有的CRUD方法。但是因为都是CRUD的标准化方法,可以通过接口和泛型,实现新的model类继承全部CRUD方法。
首先编写一个接口,新建ICRUD.cs
namespace QuickCRUD.Repos;
public interface ICRUD<T, T_ID>
{
public int GetCount();
public Task<List<T>?> GetAll();
public Task<List<T>?> GetLimit(int num);
public Task<T?> GetById(T_ID id);
public Task<int> Add(T entity);
public Task<int> Update(T entity, T_ID id);
public Task<int> DeleteById(T_ID id);
public Task<int> DeleteAll();
}然后,编写一个抽象类,AbstractRepo.cs,再抽象类中,同泛型,实现全部接口
using Microsoft.EntityFrameworkCore;
namespace QuickCRUD.Repos;
public abstract class AbstractRepo<T, T_ID>(DefaultDbContext context) : ICRUD<T, T_ID> where T : class
{
public async Task<int> Add(T entity)
{
context.Set<T>().Add(entity);
return await context.SaveChangesAsync();
}
public async Task<int> DeleteAll()
{
context.Set<T>().RemoveRange(
context.Set<T>().Take(context.Set<T>().Count())
);
return await context.SaveChangesAsync();
}
public async Task<int> DeleteById(T_ID id)
{
var w = await GetById(id);
if (w != null)
{
context.Set<T>().Remove(w);
}
return await context.SaveChangesAsync();
}
public async Task<List<T>?> GetAll()
{
return await context.Set<T>().ToListAsync();
}
public async Task<T?> GetById(T_ID id)
{
return await context.Set<T>().FindAsync(id);
}
public int GetCount()
{
return context.Set<T>().Count();
}
public async Task<List<T>?> GetLimit(int num)
{
var result = context.Set<T>().Take(num);
return await result.ToListAsync();
}
public async Task<int> Update(T entity, T_ID id)
{
var w = await GetById(id);
if (w != null)
{
context.Set<T>().Update(entity);
}
return await context.SaveChangesAsync();
}
}最后,修改WeatherForcastRepo.cs
using QuickCRUD.Models;
namespace QuickCRUD.Repos;
public class WeatherForecastRepo(DefaultDbContext context) : AbstractRepo<WeatherForecast, int>(context)
{
}WeatherForcastRepo只需要继承抽象类,即可实现全部CRUD接口方法。如果有个性化的数据库操作方法,再在repo中添加方法即可。
如果有新的model,只需要创建一个新的repo,并继承AbstractRepo即可实现全部CRUD方法。
来源:https://www.cnblogs.com/jimokelly/p/18142830
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