本文介绍了在Asp.net核心中间件中访问ModelState的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我需要访问Asp.net Core 2.1中间件中的 ModelState ，但这只能从 Controller 访问。
I need to access ModelState in Asp.net Core 2.1 Middleware, but this is just accessible from Controller.
例如，我有 ResponseFormatterMiddleware ，在此中间件中，我需要忽略 ModelState 错误并在响应消息中显示为错误：
For example I have ResponseFormatterMiddleware and in this Middleware I need to ignore ModelState error and show it's errors in 'Response Message':
public class ResponseFormatterMiddleware
{
private readonly RequestDelegate _next;
private readonly ILogger<ResponseFormatterMiddleware> _logger;
public ResponseFormatterMiddleware(RequestDelegate next, ILoggerFactory loggerFactory)
{
_next = next ?? throw new ArgumentNullException(nameof(next));
_logger = loggerFactory?.CreateLogger<ResponseFormatterMiddleware>() ?? throw new ArgumentNullException(nameof(loggerFactory));
}
public async Task Invoke(HttpContext context)
{
var originBody = context.Response.Body;
using (var responseBody = new MemoryStream())
{
context.Response.Body = responseBody;
// Process inner middlewares and return result.
await _next(context);
responseBody.Seek(0, SeekOrigin.Begin);
using (var streamReader = new StreamReader(responseBody))
{
// Get action result come from mvc pipeline
var strActionResult = streamReader.ReadToEnd();
var objActionResult = JsonConvert.DeserializeObject(strActionResult);
context.Response.Body = originBody;
// if (!ModelState.IsValid) => Get error message
// Create uniuqe shape for all responses.
var responseModel = new GenericResponseModel(objActionResult, (HttpStatusCode)context.Response.StatusCode, context.Items?["Message"]?.ToString());
// Set all response code to 200 and keep actual status code inside wrapped object.
context.Response.StatusCode = (int)HttpStatusCode.OK;
context.Response.ContentType = "application/json";
await context.Response.WriteAsync(JsonConvert.SerializeObject(responseModel));
}
}
}
}
// Extension method used to add the middleware to the HTTP request pipeline.
public static class ResponseFormatterMiddlewareExtensions
{
public static IApplicationBuilder UseResponseFormatter(this IApplicationBuilder builder)
{
return builder.UseMiddleware<ResponseFormatterMiddleware>();
}
}
[Serializable]
[DataContract]
public class GenericResponseModel
{
public GenericResponseModel(object result, HttpStatusCode statusCode, string message)
{
StatusCode = (int)statusCode;
Result = result;
Message = message;
}
[DataMember(Name = "result")]
public object Result { get; set; }
[DataMember(Name = "statusCode")]
public int StatusCode { get; set; }
[DataMember(Name = "message")]
public string Message { get; set; }
[DataMember(Name = "version")]
public string Version { get; set; } = "V1.0"
}
这是我期望的结果：
{
"result": null,
"statusCode": 400,
"message": "Name is required",
"version": "V1"
}
，但现在观察到的结果是：
but now the observed result is:
{
"result": {
"Name": [
"Name is required"
]
},
"statusCode": 400,
"message": null,
"version": "V1"
}
推荐答案
ModelState 仅在模型绑定之后可用。只需使用动作过滤器自动存储 ModelState ，即可在中间件中使用它。
ModelState is only available after model binding . Just store the ModelState automatically with an action filter , thus you can use it within middleware .
首先，添加一个操作过滤器，将ModelState设置为功能：
Firstly , add a action filter to set the ModelState as an feature :
public class ModelStateFeatureFilter : IAsyncActionFilter
{
public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
{
var state = context.ModelState;
context.HttpContext.Features.Set<ModelStateFeature>(new ModelStateFeature(state));
await next();
}
}
此处 ModelStateFeature 是持有ModelState的虚拟类：
Here the ModelStateFeature is a dummy class that holds the ModelState:
public class ModelStateFeature
{
public ModelStateDictionary ModelState { get; set; }
public ModelStateFeature(ModelStateDictionary state)
{
this.ModelState= state;
}
}
要使操作过滤器自动发生，我们需要配置MVC
to make the action filter take place automatically , we need configure the MVC
services.AddMvc(opts=> {
opts.Filters.Add(typeof(ModelStateFeatureFilter));
})
现在我们可以使用 ModelState 在您的中间件中如下：
And now we can use the ModelState within your Middleware as below:
public class ResponseFormatterMiddleware
{
// ...
public async Task Invoke(HttpContext context)
{
var originBody = context.Response.Body;
using (var responseBody = new MemoryStream())
{
context.Response.Body = responseBody;
// Process inner middlewares and return result.
await _next(context);
var ModelState = context.Features.Get<ModelStateFeature>()?.ModelState;
if (ModelState==null) {
return ; // if you need pass by , just set another flag in feature .
}
responseBody.Seek(0, SeekOrigin.Begin);
using (var streamReader = new StreamReader(responseBody))
{
// Get action result come from mvc pipeline
var strActionResult = streamReader.ReadToEnd();
var objActionResult = JsonConvert.DeserializeObject(strActionResult);
context.Response.Body = originBody;
// Create uniuqe shape for all responses.
var responseModel = new GenericResponseModel(objActionResult, (HttpStatusCode)context.Response.StatusCode, context.Items?["Message"]?.ToString());
// => Get error message
if (!ModelState.IsValid)
{
var errors= ModelState.Values.Where(v => v.Errors.Count > 0)
.SelectMany(v=>v.Errors)
.Select(v=>v.ErrorMessage)
.ToList();
responseModel.Result = null;
responseModel.Message = String.Join(" ; ",errors) ;
}
// Set all response code to 200 and keep actual status code inside wrapped object.
context.Response.StatusCode = (int)HttpStatusCode.OK;
context.Response.ContentType = "application/json";
await context.Response.WriteAsync(JsonConvert.SerializeObject(responseModel));
}
}
}
}
用简单的模型进行测试
public class MyModel {
[MinLength(6)]
[MaxLength(12)]
public string Name { get; set; }
public int Age { get; set; }
}
和一个简单的控制器：
public class HomeController : Controller
{
public IActionResult Index(string name)
{
return new JsonResult(new {
Name=name
});
}
[HttpPost]
public IActionResult Person([Bind("Age,Name")]MyModel model)
{
return new JsonResult(model);
}
}
如果我们发送带有有效负载的请求：
If we send a request with a valid payload :
POST https://localhost:44386/Home/Person HTTP/1.1
content-type: application/x-www-form-urlencoded
name=helloo&age=20
响应将是：
HTTP/1.1 200 OK
Transfer-Encoding: chunked
Content-Type: application/json
Server: Kestrel
X-SourceFiles: =?UTF-8?B?RDpccmVwb3J0XDIwMThcOVw5LTE4XEFwcFxBcHBcQXBwXEhvbWVcUGVyc29u?=
X-Powered-By: ASP.NET
{
"result": {
"name": "helloo",
"age": 20
},
"statusCode": 200,
"message": null,
"version": "V1.0"
}
如果我们发送的请求的模型无效：
And if we send a request with an invalid model :
POST https://localhost:44386/Home/Person HTTP/1.1
content-type: application/x-www-form-urlencoded
name=hello&age=i20
响应将为
HTTP/1.1 200 OK
Transfer-Encoding: chunked
Content-Type: application/json
Server: Kestrel
X-SourceFiles: =?UTF-8?B?RDpccmVwb3J0XDIwMThcOVw5LTE4XEFwcFxBcHBcQXBwXEhvbWVcUGVyc29u?=
X-Powered-By: ASP.NET
{
"result": null,
"statusCode": 200,
"message": "The value 'i20' is not valid for Age. ; The field Name must be a string or array type with a minimum length of '6'.",
"version": "V1.0"
}
这篇关于在Asp.net核心中间件中访问ModelState的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！