Blazor路由正则表达式报错求助：升级Web App后约束解析失败

问题背景 #

原Blazor WebAssembly项目按文档升级为.NET 8 Blazor Web App后，正则路由无法正常工作，但直接用Blazor Web App模板创建的项目中该正则路由可正常运行。

错误信息 #

Unhandled exception rendering component: The constraint entry 'doc' - 'regex((.)(?:/details)$)' on the route '/{{doc:regex((.)(?:/details)$)}' could not be resolved by the constraint resolver of type 'DefaultInlineConstraintResolver'.
System.InvalidOperationException: The constraint entry 'doc' - 'regex((.)(?:/details)$)' on the route '/{{doc:regex((.)(?:/details)$)})}' could not be resolved by the constraint resolver of type 'DefaultInlineConstraintResolver'.

当前路由代码 #

@attribute [Route(@"/{*doc:regex((.*)(?:\/details)$)}")]   
@rendermode InteractiveWebAssembly
[Parameter] public string doc { get; set; }

（注：原代码存在多余括号、引号的语法错误，已修正基础格式）

当前Program.cs代码 #

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddRazorComponents()
    .AddInteractiveWebAssemblyComponents();

builder.Services.AddControllers();

var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.UseWebAssemblyDebugging();
}
else
{
    app.UseExceptionHandler("/Error");
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseAntiforgery();

app.MapRazorComponents<App>()
    .AddInteractiveWebAssemblyRenderMode()
    .AddAdditionalAssemblies(typeof(Client._Imports).Assembly);
app.MapControllers();

app.Run();

问题排查与解决方案 #

1. 修正路由语法错误 #

原路由代码存在两处语法问题：

• 错误使用双大括号{{，正确应为单大括号{
• 末尾多余的冗余符号，修正后的正确路由模板如下：

@attribute [Route("/{*doc:regex((.*)(?:/details)$)}")]

2. 手动注册正则路由约束 #

Blazor Web App模板项目默认已配置正则约束，但升级后的项目遗漏了该注册步骤。在Program.cs中添加正则约束的映射：

builder.Services.AddRouting(options =>
{
    options.ConstraintMap["regex"] = typeof(Microsoft.AspNetCore.Routing.RegexRouteConstraint);
});

修改后的完整Program.cs代码：

var builder = WebApplication.CreateBuilder(args);

// 注册正则路由约束
builder.Services.AddRouting(options =>
{
    options.ConstraintMap["regex"] = typeof(Microsoft.AspNetCore.Routing.RegexRouteConstraint);
});

builder.Services.AddRazorComponents()
    .AddInteractiveWebAssemblyComponents();

builder.Services.AddControllers();

var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.UseWebAssemblyDebugging();
}
else
{
    app.UseExceptionHandler("/Error");
    app.UseHsts();
}

app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseAntiforgery();

app.MapRazorComponents<App>()
    .AddInteractiveWebAssemblyRenderMode()
    .AddAdditionalAssemblies(typeof(Client._Imports).Assembly);
app.MapControllers();

app.Run();

3. 验证正则表达式逻辑 #

当前正则(.*)(?:\/details)$用于匹配以/details结尾的路径，若实际业务需要调整匹配规则，可直接修改正则表达式内容。

内容的提问来源于stack exchange，提问作者Артём Цибульский