未能将约束引用'string‘解析为类型。(netcoreapp3.0)

Question

我有一个错误。这是我的启动课。

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers();
}

public void Configure(IApplicationBuilder app)
{
    app.UseDeveloperExceptionPage();

    app.UseRouting();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}

当前的技术是"netcoreapp3.0“，我的控制器是。

[Route("api/[controller]")]
[ApiController]
public class ExampleController : ControllerBase
{
    [HttpGet("request")]
    public ActionResult Index()
    {
        return Ok();
    }
}

这就是我的错误。我找不到解决方案，我甚至不知道这到底是什么。所以我们到了这里。

System.InvalidOperationException: The constraint reference 'string' could not be resolved to a type. Register the constraint type with 'Microsoft.AspNetCore.Routing.RouteOptions.ConstraintMap'.
   at Microsoft.AspNetCore.Routing.DefaultParameterPolicyFactory.Create(RoutePatternParameterPart parameter, String inlineText)
   at Microsoft.AspNetCore.Routing.ParameterPolicyFactory.Create(RoutePatternParameterPart parameter, RoutePatternParameterPolicyReference reference)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.CreateCandidate(Endpoint endpoint, Int32 score)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.CreateCandidates(IReadOnlyList`1 endpoints)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.AddNode(DfaNode node, DfaState[] states, Int32 exitDestination)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.AddNode(DfaNode node, DfaState[] states, Int32 exitDestination)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.<AddNode>g__Transition|19_0(DfaNode next, <>c__DisplayClass19_0& )
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.AddNode(DfaNode node, DfaState[] states, Int32 exitDestination)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.AddNode(DfaNode node, DfaState[] states, Int32 exitDestination)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.AddNode(DfaNode node, DfaState[] states, Int32 exitDestination)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.AddNode(DfaNode node, DfaState[] states, Int32 exitDestination)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherBuilder.Build()
   at Microsoft.AspNetCore.Routing.Matching.DataSourceDependentMatcher.CreateMatcher(IReadOnlyList`1 endpoints)
   at Microsoft.AspNetCore.Routing.DataSourceDependentCache`1.Initialize()
   at System.Threading.LazyInitializer.EnsureInitializedCore[T](T& target, Boolean& initialized, Object& syncLock, Func`1 valueFactory)
   at System.Threading.LazyInitializer.EnsureInitialized[T](T& target, Boolean& initialized, Object& syncLock, Func`1 valueFactory)
   at Microsoft.AspNetCore.Routing.Matching.DataSourceDependentMatcher..ctor(EndpointDataSource dataSource, Lifetime lifetime, Func`1 matcherBuilderFactory)
   at Microsoft.AspNetCore.Routing.Matching.DfaMatcherFactory.CreateMatcher(EndpointDataSource dataSource)
   at Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.InitializeCoreAsync()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.<Invoke>g__AwaitMatcher|8_0(EndpointRoutingMiddleware middleware, HttpContext httpContext, Task`1 matcherTask)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

编辑:这是我的依赖项。当我移除它们的时候，它就起作用了。

<PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="3.0.0" />
<PackageReference Include="Microsoft.AspNetCore.Identity.EntityFrameworkCore" Version="3.1.0" />
<PackageReference Include="Microsoft.EntityFrameworkCore" Version="3.1.0" />
<PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="3.1.0">
  <PrivateAssets>all</PrivateAssets>
  <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>
<PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1.0" />
<PackageReference Include="Microsoft.EntityFrameworkCore.Tools" Version="3.0.0">
  <PrivateAssets>all</PrivateAssets>
  <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>
<PackageReference Include="Microsoft.Extensions.Caching.SqlServer" Version="3.1.0" />
<PackageReference Include="Microsoft.Extensions.Logging.Debug" Version="3.0.0" />
<PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="3.0.0" />
<PackageReference Include="Swashbuckle.AspNetCore.Swagger" Version="5.0.0-rc4" />
<PackageReference Include="Swashbuckle.AspNetCore.SwaggerUI" Version="5.0.0-rc4" />
<PackageReference Include="Z.EntityFramework.Plus.EFCore" Version="3.0.24" />
<PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
<PackageReference Include="Swashbuckle.AspNetCore" Version="5.0.0-rc4" />

Answer 1

以防您使用类似于

[HttpGet("example/{param1:string}/{param2:Guid}")]

将其更改为

[HttpGet("example/{param1}/{param2:Guid}")]

因为“：regex-validation-constraint”实际上被解释为字符串，而验证器不是类型定义验证器，所以一切都以字符串的形式到达服务器，并且没有-regex- :)

Answer 2

我最近也遇到了这个问题。我的修复方法是使用"alpha“作为字符串类型的替代：

[HttpGet("example/{param1:alpha}")]

Microsoft documentation中记录了这一点。

Answer 3

它可以是参数名称和类型之间的空格。

示例：

{param1 :alpha}

{param1:alpha}✅