在 ASP.NET Web API 中处理 ModelState 验证

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Like this, for example:

public HttpResponseMessage Post(Person person)
{
if (ModelState.IsValid)
{
PersonDB.Add(person);
return Request.CreateResponse(HttpStatusCode.Created, person);
}
else
{
// the code below should probably be refactored into a GetModelErrors
// method on your BaseApiController or something like that


var errors = new List<string>();
foreach (var state in ModelState)
{
foreach (var error in state.Value.Errors)
{
errors.Add(error.ErrorMessage);
}
}
return Request.CreateResponse(HttpStatusCode.Forbidden, errors);
}
}

This will return a response like this (assuming JSON, but same basic principle for XML):

HTTP/1.1 400 Bad Request
Content-Type: application/json; charset=utf-8
(some headers removed here)


["A value is required.","The field First is required.","Some custom errorm essage."]

You can of course construct your error object/list any way you like, for example adding field names, field id's etc.

Even if it's a "one way" Ajax call like a POST of a new entity, you should still return something to the caller - something that indicates whether or not the request was successful. Imagine a site where your user will add some info about themselves via an AJAX POST request. What if the information they have tried to entered isn't valid - how will they know if their Save action was successful or not?

The best way to do this is using Good Old HTTP Status Codes like 200 OK and so on. That way your JavaScript can properly handle failures using the correct callbacks (error, success etc).

Here's a nice tutorial on a more advanced version of this method, using an ActionFilter and jQuery: http://asp.net/web-api/videos/getting-started/custom-validation

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最佳答案

For separation of concern, I would suggest you use action filter for model validation, so you don't need to care much how to do validation in your api controller:

using System.Net;
using System.Net.Http;
using System.Web.Http.Controllers;
using System.Web.Http.Filters;


namespace System.Web.Http.Filters
{
public class ValidationActionFilter : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext actionContext)
{
var modelState = actionContext.ModelState;


if (!modelState.IsValid)
actionContext.Response = actionContext.Request
.CreateErrorResponse(HttpStatusCode.BadRequest, modelState);
}
}
}

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Maybe not what you were looking for, but perhaps nice for someone to know:

If you are using .net Web Api 2 you could just do the following:

if (!ModelState.IsValid)
return BadRequest();

Depending on the model errors, you get this result:

{
Message: "The request is invalid."
ModelState: {
model.PropertyA: [
"The PropertyA field is required."
],
model.PropertyB: [
"The PropertyB field is required."
]
}
}

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You can also throw exceptions as documented here: http://blogs.msdn.com/b/youssefm/archive/2012/06/28/error-handling-in-asp-net-webapi.aspx

Note, to do what that article suggests, remember to include System.Net.Http

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You can use attributes from the System.ComponentModel.DataAnnotations namespace to set validation rules. Refer Model Validation - By Mike Wasson for details.

Also refer video ASP.NET Web API, Part 5: Custom Validation - Jon Galloway

Other References

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I had an issue implementing the accepted solution pattern where my ModelStateFilter would always return false (and subsequently a 400) for actionContext.ModelState.IsValid for certain model objects:

public class ModelStateFilter : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext actionContext)
{
if (!actionContext.ModelState.IsValid)
{
actionContext.Response = new HttpResponseMessage { StatusCode = HttpStatusCode.BadRequest};
}
}
}

I only accept JSON, so I implemented a custom model binder class:

public class AddressModelBinder : System.Web.Http.ModelBinding.IModelBinder
{
public bool BindModel(HttpActionContext actionContext, System.Web.Http.ModelBinding.ModelBindingContext bindingContext)
{
var posted = actionContext.Request.Content.ReadAsStringAsync().Result;
AddressDTO address = JsonConvert.DeserializeObject<AddressDTO>(posted);
if (address != null)
{
// moar val here
bindingContext.Model = address;
return true;
}
return false;
}
}

Which I register directly after my model via

config.BindParameter(typeof(AddressDTO), new AddressModelBinder());

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Here you can check to show the model state error one by one

 public HttpResponseMessage CertificateUpload(employeeModel emp)
{
if (!ModelState.IsValid)
{
string errordetails = "";
var errors = new List<string>();
foreach (var state in ModelState)
{
foreach (var error in state.Value.Errors)
{
string p = error.ErrorMessage;
errordetails = errordetails + error.ErrorMessage;


}
}
Dictionary<string, object> dict = new Dictionary<string, object>();






dict.Add("error", errordetails);
return Request.CreateResponse(HttpStatusCode.BadRequest, dict);




}
else
{
//do something
}
}

}

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C#

    public class ValidateModelAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext actionContext)
{
if (actionContext.ModelState.IsValid == false)
{
actionContext.Response = actionContext.Request.CreateErrorResponse(
HttpStatusCode.BadRequest, actionContext.ModelState);
}
}
}

...

    [ValidateModel]
public HttpResponseMessage Post([FromBody]AnyModel model)
{

Javascript

$.ajax({
type: "POST",
url: "/api/xxxxx",
async: 'false',
contentType: "application/json; charset=utf-8",
data: JSON.stringify(data),
error: function (xhr, status, err) {
if (xhr.status == 400) {
DisplayModelStateErrors(xhr.responseJSON.ModelState);
}
},
....




function DisplayModelStateErrors(modelState) {
var message = "";
var propStrings = Object.keys(modelState);


$.each(propStrings, function (i, propString) {
var propErrors = modelState[propString];
$.each(propErrors, function (j, propError) {
message += propError;
});
message += "\n";
});


alert(message);
};

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Or, if you are looking for simple collection of errors for your apps.. here is my implementation of this:

public override void OnActionExecuting(HttpActionContext actionContext)
{
var modelState = actionContext.ModelState;


if (!modelState.IsValid)
{


var errors = new List<string>();
foreach (var state in modelState)
{
foreach (var error in state.Value.Errors)
{
errors.Add(error.ErrorMessage);
}
}


var response = new { errors = errors };


actionContext.Response = actionContext.Request
.CreateResponse(HttpStatusCode.BadRequest, response, JsonMediaTypeFormatter.DefaultMediaType);
}
}

Error Message Response will look like:

{
"errors": [
"Please enter a valid phone number (7+ more digits)",
"Please enter a valid e-mail address"
]
}

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Add below code in startup.cs file

services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2).ConfigureApiBehaviorOptions(options =>
{
options.InvalidModelStateResponseFactory = (context) =>
{
var errors = context.ModelState.Values.SelectMany(x => x.Errors.Select(p => new ErrorModel()
{
ErrorCode = ((int)HttpStatusCode.BadRequest).ToString(CultureInfo.CurrentCulture),
ErrorMessage = p.ErrorMessage,
ServerErrorMessage = string.Empty
})).ToList();
var result = new BaseResponse
{
Error = errors,
ResponseCode = (int)HttpStatusCode.BadRequest,
ResponseMessage = ResponseMessageConstants.VALIDATIONFAIL,


};
return new BadRequestObjectResult(result);
};
});

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Put this in the startup.cs file

 services.AddMvc().ConfigureApiBehaviorOptions(options =>
{
options.InvalidModelStateResponseFactory = (context) =>
{
var errors = context.ModelState.Values.SelectMany(x => x.Errors.Select(p =>p.ErrorMessage)).ToList();
var result = new Response
{
Succeeded = false,
ResponseMessage = string.Join(", ",errors)
};
return new BadRequestObjectResult(result);
};
});