.NET7之MiniAPI(特别篇)：.NET7 Preview3

.NET7的第三个预览版发布了，同样带来了mini api的更新，这次带来了路由过滤器，与mvc版的action 过滤器相似。具体见https://devblogs.microsoft.com/dotnet/asp-net-core-updates-in-dotnet-7-preview-3/

用官方的代码，跑不起来，这样那样的问题，比如下面的代码，直接报空引用的异常。

app.MapGet("/data0/{no}", (string no) =>
{Console.WriteLine($"Get方法中：no={no}");return new Data { No = no, Name = "test" + DateTime.Now };}).AddFilter((RouteHandlerInvocationContext context, RouteHandlerFilterDelegate next) =>{var no = (string?)context.Parameters[0];Console.WriteLine($"Get方法前：no={no}");if (no != null && !no.StartsWith("NO")){return new ValueTask<object?>("no is error!");}var result = next(context);if (result.IsCompleted){Console.WriteLine($"Get方法后：结果={result.Result}");}return result;});

经过一阵折腾，终于正常的跑了起来，需要把map的方法独立出来写才可以。同时这里使用了三种方式来使用过滤器，换汤不换药，本质一样。

var builder = WebApplication.CreateBuilder(args);var app = builder.Build();Data GetData(string no)
{Console.WriteLine($"Get方法中：no={no}");return new Data { No = no, Name = "test" + DateTime.Now };
};
//第一种方式
app.MapGet("/data1/{no}", GetData).AddFilter((RouteHandlerInvocationContext context, RouteHandlerFilterDelegate next) =>{var no = (string?)context.Parameters[0];Console.WriteLine($"Get方法前：no={no}");if (no != null && !no.StartsWith("NO")){return new ValueTask<object?>("no is error!");}var result = next(context);if (result.IsCompleted){Console.WriteLine($"Get方法后：结果={result.Result}");}return result;});string AddTest(Data data)
{Console.WriteLine($"Post方法中：no={data.No}");return "OK";
}
app.MapPost("/data1", AddTest).AddFilter((RouteHandlerInvocationContext context, RouteHandlerFilterDelegate next) =>{var data = (Data?)context.Parameters[0];Console.WriteLine($"Post方法前：data={data}");var result = next(context);if (result.IsCompleted){Console.WriteLine($"Post方法后：结果={result.Result}");}return result;});
//第二种方式
app.MapGet("/data2/{no}", GetData)
.AddFilter((RouteHandlerContext routeHandlerContext, RouteHandlerFilterDelegate next) =>
{return (context) =>{var no = (string?)context.Parameters[0];if (no != null && !no.StartsWith("NO")){return new ValueTask<object?>("no is error!");}return next(context);};
});
//第三种方式
app.MapGet("/data3/{name}", GetData).AddFilter<MyFilter>();app.Run();public class MyFilter : IRouteHandlerFilter
{public ValueTask<object?> InvokeAsync(RouteHandlerInvocationContext context, RouteHandlerFilterDelegate next){var no = (string?)context.Parameters[0];if (no != null && !no.StartsWith("NO")){return new ValueTask<object?>("no is error!");}return next(context);}
}public record Data
{public string No { get; set; }public string Name { get; set; }
}