Problem detail service middleware sample code

fundamentals/middleware/problem-details-service/ProblemDetailService.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net7.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <RootNamespace>ProblemDetailsServiceSample</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="7.0.0-preview.7.22376.6" />
+    <PackageReference Include="Swashbuckle.AspNetCore" Version="6.2.3" />
+  </ItemGroup>
+
+</Project>

fundamentals/middleware/problem-details-service/Program.cs

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+using Microsoft.AspNetCore.Http.Features;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// Add services to the container.
+// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
+builder.Services.AddEndpointsApiExplorer();
+builder.Services.AddSwaggerGen();
+builder.Services.AddProblemDetails(options =>
+    options.CustomizeProblemDetails = (context) =>
+    {
+        var mathErrorFeature = context.HttpContext.Features.GetRequiredFeature<MathErrorFeature>();
+        (string Detail, string Type) details = mathErrorFeature.MathError switch
+        {
+            MathErrorType.DivisionByZeroError => ("The number you inputed is zero", "https://en.wikipedia.org/wiki/Division_by_zero"),
+            _ => ("Negative or complex numbers are not handled", "https://en.wikipedia.org/wiki/Square_root")
+        };
+
+        context.ProblemDetails.Type = details.Type;
+        context.ProblemDetails.Title = "Wrong Input";
+        context.ProblemDetails.Detail = details.Detail;
+    });
+
+var app = builder.Build();
+
+// Configure the HTTP request pipeline.
+if (app.Environment.IsDevelopment())
+{
+    app.UseSwagger();
+    app.UseSwaggerUI();
+}
+
+app.UseHttpsRedirection();
+
+// middleware to handle writing problem details to the response
+app.Use(async (context, next) =>
+{
+    // added the MathErrorFeature to the request pipeline
+    var mathErrorFeature = new MathErrorFeature();
+    context.Features.Set(mathErrorFeature);
+    await next(context);
+});
+
+app.UseStatusCodePages();
+
+// endpoint for dividing numbers
+app.MapGet("/divide", (HttpContext context, double numerator, double denominator) =>
+{
+    if (denominator == 0)
+    {
+        context.Features.GetRequiredFeature<MathErrorFeature>().MathError = MathErrorType.DivisionByZeroError;
+        return Results.BadRequest();
+    }
+
+    var calculation = numerator / denominator;
+    return Results.Ok(calculation);
+});
+
+// endpoint for obtaining the squareroot of a number
+app.MapGet("/squareroot", (HttpContext context, int radicand) =>
+{
+    if (radicand < 0)
+    {
+        context.Features.GetRequiredFeature<MathErrorFeature>().MathError = MathErrorType.NegativeRadicandError;
+        return Results.BadRequest();
+    }
+
+    var calculation = Math.Sqrt(radicand);
+    return Results.Ok(calculation);
+});
+
+app.Run();
+
+// Custom math errors
+enum MathErrorType
+{
+    DivisionByZeroError,
+    NegativeRadicandError
+}
+
+// Custom Http Request Feature
+class MathErrorFeature
+{
+    public MathErrorType MathError { get; set; }
+}

fundamentals/middleware/problem-details-service/appsettings.Development.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

fundamentals/middleware/problem-details-service/appsettings.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}