ASP.NET Core应用程序1：创建示例项目

1 创建项目

创建一个MyWebApp的空项目。也可以用一下命令行创建。

dotnet new globaljson --sdk-version 3.1 --output MyWebApp
已成功创建模板“global.json file”。
dotnet new web --no-https --output MyWebApp --framework netcoreapp3.1
已成功创建模板“ASP.NET Core Empty”。
dotnet new sln -o MyWebApp
已成功创建模板“解决方案文件”。

dotnet sln MyWebApp add MyWebApp
已将项目“WebApp.csproj”添加到解决方案中。

2 添加数据模型

2.1 添加数据库NuGet包

Microsoft.EntityFrameworkCore.Design3.1.1版本

Microsoft.EntityFrameworkCore.SqlServer3.1.1版本

2.2 创建数据模型

在Models文件夹中创建三个类：Product、Supplier、Category。

/// <summary>
/// 产品
/// </summary>
public class Product
{
    public long ProductId { get; set; }

    public string Name { get; set; }
    [Column(TypeName = "decimal(8, 2)")]
    public decimal Price { get; set; }

    public long CategoryId { get; set; }
    public Category Category { get; set; }

    public long SupplierId { get; set; }
    public Supplier Supplier { get; set; }
}
/// <summary>
/// 供应商
/// </summary>
public class Supplier
{
    public long SupplierId { get; set; }
    public string Name { get; set; }
    public string City { get; set; }

    public IEnumerable<Product> Products { get; set; }
}
/// <summary>
/// 类别
/// </summary>
public class Category
{
    public long CategoryId { get; set; }
    public string Name { get; set; }

    public IEnumerable<Product> Products { get; set; }
}

Models文件夹中创建一个能访问数据库的EFCore上下文类DataContext。

public class DataContext : DbContext
    {
    public DataContext(DbContextOptions<DataContext> options) : base(options)
    {         
    }
    public DbSet<Product> Products { get; set; }    
    public DbSet<Supplier> Suppliers { get; set; }
    public DbSet<Category> Categories { get; set; } 
}

2.3 准备种子数据

Models文件夹中创建SeedData类，用来定义填充的种子数据。

    public static class SeedData
    {
        public static void SeedDatabase(DataContext context)
        {
            context.Database.Migrate();
            if (context.Products.Count() == 0 && context.Suppliers.Count() == 0 &&
                context.Categories.Count() == 0)
            {
                Supplier s1 = new Supplier { Name = "Splash Dudes", City = "San Jose" };
                Supplier s2 = new Supplier { Name = "Soccer Town", City = "Chicago" };
                Supplier s3 = new Supplier { Name = "Chess Co", City = "New York" };

                Category c1 = new Category { Name = "Watersports" };
                Category c2 = new Category { Name = "Soccer" };
                Category c3 = new Category { Name = "Chess" };

                context.Products.AddRange(
                    new Product { Name = "Kayak", Price = 275, Category = c1, Supplier = s1 },
                    new Product { Name = "Lifejacket", Price = 48.95m, Category = c1, Supplier = s1 },
                    new Product { Name = "Soccer Ball", Price = 19.50m, Category = c2, Supplier = s2 },
                    new Product { Name = "Corner Flags", Price = 34.95m, Category = c2, Supplier = s2 },
                    new Product { Name = "Stadium", Price = 79500, Category = c2, Supplier = s2 },
                    new Product { Name = "Thinking Cap", Price = 16, Category = c3, Supplier = s3 },
                    new Product { Name = "Unsteady Chair", Price = 29.95m, Category = c3, Supplier = s3 },
                    new Product { Name = "Human Chess Board", Price = 75, Category = c3, Supplier = s3 },
                    new Product { Name = "Bling-Bling King", Price = 1200, Category = c3, Supplier = s3 }
                );
                context.SaveChanges();
            }
        }
    }

2.4 配置EFCore服务和中间件

对Startup类进行更改

    public class Startup
    {
        public IConfiguration Configuration { get; set; }
        public Startup(IConfiguration config)
        {
            Configuration = config;
        }
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddDbContext<DataContext>(opts =>
            {
                opts.UseSqlServer(Configuration["ConnectionStrings:ProductConnection"]);
                opts.EnableSensitiveDataLogging(true);
            });
        }
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env, DataContext context)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapGet("/", async context =>
                {
                    await context.Response.WriteAsync("Hello World!");
                });
            });

            SeedData.SeedDatabase(context);
        }
    }

在appsettings.json中定义配置字符串

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information",
      "Microsoft.EntityFrameworkCore": "Information"
    }
  },
  "AllowedHosts": "*",
  "ConnectionStrings": {
    "ProductConnection": "Server=.;Database=Products;MultipleActiveResultSets=true;User ID=sa;Pwd=123456;"
  }
}

2.5 创建和应用迁移

在WebApp项目文件夹中运行命令

创建迁移 dotnet ef migrations add Initial

将迁移应用到数据库dotnet ef database update

如果需要重置数据库，可运行dotnet ef database drop -force

3 添加CSS框架

安装LibMan工具包 Microsoft.Web.LibraryManager.Cli2.0.96

命令

dotnet tool uninstall --global Microsoft.Web.LibraryManager.Cli
dotnet tool install --global Microsoft.Web.LibraryManager.Cli --version 2.0.96

安装引导CSS框架

命令

libman init -p cdnjs

libman install twitter-bootstrap@4.3.1 -d wwwroot/lib/twitter-bootstrap

或者在VS中选择添加客户端库

4 配置请求管道

定义一个简单中间件TestMiddleware.cs.

public class TestMiddleware
{
    private RequestDelegate _nextDelegate;
    public TestMiddleware(RequestDelegate nextDelegate)
    {
        _nextDelegate = nextDelegate;
    }

    public async Task Invoke(HttpContext context,DataContext dataContext)
    {
        if(context.Request.Path == "/test")
        {
                await context.Response.WriteAsync($"There are {dataContext.Products.Count()} products\n");
                await context.Response.WriteAsync($"There are {dataContext.Categories.Count()} categories\n");
                await context.Response.WriteAsync($"There are {dataContext.Suppliers.Count()} suppliers\n");
        }
        else
        {
            await _nextDelegate(context);
        }
    }
}

在Startup类中添加这个中间件组件

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env, DataContext context)
        {
            ......
            app.UseRouting();
            app.UseMiddleware<TestMiddleware>();
            ......  
        }

5 运行项目