I have following working code:
public ObjectResult GetDocumentById([ModelBinder(BinderType = typeof(CustomModelBinder))] CustomId id)
How can I specify CustomModelBinder to be the default binder for CustomId type?
Have you tried decorating your CustomId class with ModelBinderAttribute?
[ModelBinder(BinderType = typeof(CustomModelBinder))]
public class CustomId { }
You can also register your model binder directly in ConfigureServices in your Startup class (note that IModelBinderProvider no longer exists in ASP.NET 5):
public void ConfigureServices(IServiceCollection services) {
services.ConfigureMvc(options => {
options.ModelBinders.Insert(0, new CustomModelBinder());
});
}
Since your model binder will be the first one to be invoked, return null when it cannot handle the model type to make sure the built-in binders will still be invoked for other types:
public class CancellationTokenModelBinder : IModelBinder
{
/// <inheritdoc />
public Task<ModelBindingResult> BindModelAsync(ModelBindingContext bindingContext)
{
if (bindingContext.ModelType == typeof(CancellationToken))
{
var model = bindingContext.OperationBindingContext.HttpContext.RequestAborted;
var validationNode =
new ModelValidationNode(bindingContext.ModelName, bindingContext.ModelMetadata, model);
return Task.FromResult(new ModelBindingResult(
model,
bindingContext.ModelName,
isModelSet: true,
validationNode: validationNode));
}
return Task.FromResult<ModelBindingResult>(null);
}
}
Here is an example to have a custom binder that, instead of null, binds empty string to the properties of type string
public Task<ModelBindingResult> BindModelAsync(ModelBindingContext bindingContext)
{
var key = bindingContext.ModelName;
var value = bindingContext.ValueProvider.GetValue(key);
if ((bindingContext.ModelType == typeof(string)) && (string.IsNullOrWhiteSpace(value.FirstValue)))
{
var result = ModelBindingResult.Success(key, string.Empty);
return Task.FromResult<ModelBindingResult>(result);
}
return Task.FromResult<ModelBindingResult>(default(ModelBindingResult));
}
Note that compared to the answer posted above, in DNX 1.0.0-rc1-update1, the line
return Task.FromResult<ModelBindingResult>(null);
causes a compile error because ModelBindingResult is a struct (a non-nullable value type).
Try changing it to the following in order to fix the compile error
return Task.FromResult<ModelBindingResult>(default(ModelBindingResult));
Related
I tried to convert ASP.NET WEB API to ASP.NET CORE WEB API and have errors
My code in ASP.NET WebAPI
public class TestController : ApiController
{
// GET /test
public object Get()
{
return "get";
}
// GET /test?id={id}
public object Get(string id)
{
return id;
}
// GET /test?id={id}&anyParam={anyParam}
public object Get(string id, string anyParam)
{
return id + anyParam;
}
}
config.Routes.MapHttpRoute("Controller", "{controller}");
Try to convert it to ASP.NET Core 2.1 / 3.0
[ApiController]
[Route("{controller}")]
public class TestController : ControllerBase
{
// GET /test
public object Get()
{
return "get";
}
// GET /test?id={id}
public object Get(string id)
{
return id;
}
// GET /test?id={id}&anyParam={anyParam}
public object Get(string id, string anyParam)
{
return id + anyParam;
}
}
services.AddControllers();
app.UseRouting();
app.UseEndpoints(endpoints => { endpoints.MapControllers(); });
And i have in ASP.NET Core
AmbiguousMatchException: The request matched multiple endpoints
The sensible solution is just have one method that takes three parameters.
But, sensible solutions don't make for the most interesting stackoverflow answers, so here is how you can do this with two custom attributes, one which states the parameters that are required, and another which states which parameters are excluded:
public class RequireRequestParameterAttribute : ActionMethodSelectorAttribute
{
private readonly string[] _requiredNames;
public RequireRequestParameterAttribute(params string[] names)
{
this._requiredNames = names;
}
public override bool IsValidForRequest(
RouteContext routeContext,
ActionDescriptor action
) =>
this._requiredNames
.All(
routeContext
.HttpContext
.Request
.Query
.ContainsKey
);
}
public class DisallowRequestParameterAttribute : ActionMethodSelectorAttribute
{
private readonly string[] _forbiddenNames;
public DisallowRequestParameterAttribute(params string[] names)
{
this._forbiddenNames = names;
}
public override bool IsValidForRequest(
RouteContext routeContext,
ActionDescriptor action
) =>
!(this._forbiddenNames
.Any(
routeContext
.HttpContext
.Request
.Query
.ContainsKey
)
);
}
Now you can apply the attributes as follows:
[ApiController]
[Route("[controller]")]
public class TestController : ControllerBase
{
// GET test
public object Get()
{
return "Get";
}
// GET test?id={id}
[RequireRequestParameter("id")]
[DisallowRequestParameter("anyParam")]
public object Get(string id)
{
return id;
}
// GET test?id={id}&anyParam={anyParam}
[RequireRequestParameter("id", "anyParam")]
public object Get(string id, string anyParam)
{
return $"{id}: {anyParam}";
}
}
This means if you add another method with a third parameter, you have the maintenance burden of adding or modifying the DisallowRequestParameter attribute on the other methods.
I look your generated urls on actions and they are both /test which cause AmbiguousMatchException because your parameters are GET and are optional.
I think you can have same names on actions but you need define different ROUTE attribute (diff urls) on actions. Eg. you can not use default route with polymorphism on controller actions.
[Route("Home/About")]
MVC controllers Mapping of controllers now takes place inside
UseEndpoints.
Add MapControllers if the app uses attribute routing.
Source
https://learn.microsoft.com/cs-cz/aspnet/core/mvc/controllers/routing?view=aspnetcore-3.0#attribute-routing
Thanks to daremachine with his answer I was able to find information on Google
First step in ASP.NET Core we need class which inherit ActionMethodSelectorAttribute
public class RequireRequestValueAttribute : ActionMethodSelectorAttribute
{
public RequireRequestValueAttribute(string name, string value = null)
{
Name = name;
Value = value;
}
public string Name { get; }
public string Value { get; }
public StringComparison ComparisonType { get; } = StringComparison.OrdinalIgnoreCase;
private bool ValueIsValid(object value)
{
return ValueIsValid(value?.ToString());
}
private bool ValueIsValid(string value)
{
if (Value == null)
{
return true;
}
return string.Equals(value, Value, ComparisonType);
}
public override bool IsValidForRequest(RouteContext routeContext, ActionDescriptor action)
{
var value = default(object);
if (routeContext.RouteData.Values.TryGetValue(Name, out value) && ValueIsValid(value))
return true;
if (routeContext.RouteData.DataTokens.TryGetValue(Name, out value) && ValueIsValid(value))
return true;
if (routeContext.HttpContext.Request.Query.ContainsKey(Name))
{
var values = routeContext.HttpContext.Request.Query[Name];
if (values.Count <= 0)
{
if (ValueIsValid(null))
return true;
}
else if (values.Any(v => ValueIsValid(v)))
return true;
}
return false;
}
}
Then we can add to question methods [RequireRequestValue("")], the controller will look like this
[ApiController]
[Route("{controller}")]
public class TestController : ControllerBase
{
// GET /test
public object Get()
{
return "get";
}
// GET /test?id={id}
[RequireRequestValue("id")]
public object Get(string id)
{
return id;
}
}
But it can't polymorphism two similar fields, type id in my question
For asp net core 2. If you try to implement the same logic as was in web api controllers then use Microsoft.AspNetCore.Mvc.WebApiCompatShim. This nuget package provides compatibility in ASP.NET Core MVC with ASP.NET Web API 2 to simplify migration of existing Web API implementations. Please check this answer. Starting with ASP.NET Core 3.0, the Microsoft.AspNetCore.Mvc.WebApiCompatShim package is no longer available.
My requirement is when the return type of the action is void or Task, I'd like to return my custom ApiResult instead. I tried the middleware mechanism, but the response I observed has null for both ContentLength and ContentType, while what I want is a json representation of an empty instance of ApiResult.
Where should I make this conversion then?
There are multiple filter in .net core, and you could try Result filters.
For void or Task, it will return EmptyResult in OnResultExecutionAsync.
Try to implement your own ResultFilter like
public class ResponseFilter : IAsyncResultFilter
{
public async Task OnResultExecutionAsync(ResultExecutingContext context, ResultExecutionDelegate next)
{
// do something before the action executes
if (context.Result is EmptyResult)
{
context.Result = new JsonResult(new ApiResult());
}
var resultContext = await next();
// do something after the action executes; resultContext.Result will be set
}
}
public class ApiResult
{
public int Code { get; set; }
public object Result { get; set; }
}
And register it in Startup.cs
services.AddScoped<ResponseFilter>();
services.AddMvc(c =>
{
c.Filters.Add(typeof(ResponseFilter));
}).SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
All you have to do is to check the return type and on the basis of the return you can perform whatever operations you want.
Here is the abstract demo:
You have a method:
public Action SomeActionMethod()
{
var obj = new object();
return (Action)obj;
}
Now in your code you can use the following code to get the name of the method:
MethodBase b = p.GetType().GetMethods().FirstOrDefault();
var methodName = ((b as MethodInfo).ReturnType.Name);
Where p in the above code is the class which contains the methods whose return type you want to know.
after having the methodname you can decide on variable methodName what to return.
Hope it helps.
I'm having a problem trying to get custom model binders to work as a query parameter like I have gotten to work previously in .net framework 4.7.
To ensure this wasn't a scenario where my object was too complex, I reduced the model to a simple string but even then I cannot get this to work.
I have a simple model I would like to be binded from query parameters.
public class SearchModel {
public string SearchTerms { get; set; }
}
And I have configured the ModelBinder and ModelBinderProvider as shown here like so.
public class TestModelBinder : IModelBinder {
public Task BindModelAsync(ModelBindingContext bindingContext) {
if (bindingContext.ModelType != typeof(SearchModel)) {
throw new ArgumentException($"Invalid binding context supplied {bindingContext.ModelType}");
}
var model = (SearchModel)bindingContext.Model ?? new SearchModel();
var properties = model.GetType().GetProperties();
foreach(var p in properties) {
var value = this.GetValue(bindingContext, p.Name);
p.SetValue(model, Convert.ChangeType(value, p.PropertyType), null);
}
return Task.CompletedTask;
}
protected string GetValue(ModelBindingContext context, string key) {
var result = context.ValueProvider.GetValue(key);
return result.FirstValue;
}
}
public class TestModelBinderProvider : IModelBinderProvider {
public IModelBinder GetBinder(ModelBinderProviderContext context) {
if (context == null) {
throw new ArgumentNullException(nameof(context));
}
if (context.Metadata.ModelType == typeof(SearchModel)) {
var returnType = new BinderTypeModelBinder(typeof(TestModelBinder));
return returnType;
}
return null;
}
}
As stated in the last step in Microsoft documentation I updated my ConfigureServices method in Startup.cs to include the BinderProvider.
services.AddMvc(options => {
options.ModelBinderProviders.Insert(0, new TestModelBinderProvider());
})
.SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
But when I call my Search endpoint with a url such as "https://localhost:44387/api/testbinding?searchTerms=newSearch" I am always seeing a return of "request == null True" even though I see it properly hit the custom binding and bind correctly if I step through debugging, can anyone please point me in the right direction as to what I am doing wrong?
[Route("api/[controller]")]
[ApiController]
public class TestBindingController : ControllerBase {
[HttpGet()]
public IActionResult GetResult([FromQuery] SearchModel request) {
return Ok($"request == null {request == null}");
}
}
I think what you're missing if the statement that sets the result of the model binding operation, as you can see in the AuthorEntityBinder code sample in this section of the docs:
bindingContext.Result = ModelBindingResult.Success(model);
Your implementation of the model binder does create an instance of SearchModel, but doesn't feed it back to the model binding context.
As a separate note, I don't think you need to add a custom model binder is the query string segments match the properties names of the model you're trying to bind.
In ASP.Net MVC 5, custom data annotation validator can be implemented by inheriting DataAnnotationsModelValidator and registering using DataAnnotationsModelValidatorProvider.RegisterAdapter(...). In ASP.Net Core MVC, how can I achieve this?
I found similar question at ASP.net core MVC 6 Data Annotations separation of concerns, but can anyone show me simple example code?
It seems to me ASP.NET Core MVC does not have support for DataAnnotationsModelValidatorProvider.RegisterAdapter anymore. The solution I discovered is as follows:
Suppose I want to change the Validator for RequiredAttribute to my own validator adaptor (MyRequiredAttributeAdaptor), Change the default error message of EmailAddressAttribute, and change the Localized Error Message Source for 'CompareAttribute' to my own message.
1- Create a custom ValidationAttributeAdapterProvider
using Microsoft.AspNetCore.Mvc.DataAnnotations;
using Microsoft.AspNetCore.Mvc.DataAnnotations.Internal;
using Microsoft.Extensions.Localization;
using System.ComponentModel.DataAnnotations;
public class CustomValidationAttributeAdapterProvider
: ValidationAttributeAdapterProvider, IValidationAttributeAdapterProvider
{
public CustomValidationAttributeAdapterProvider() { }
IAttributeAdapter IValidationAttributeAdapterProvider.GetAttributeAdapter(
ValidationAttribute attribute,
IStringLocalizer stringLocalizer)
{
IAttributeAdapter adapter;
if (attribute is RequiredAttribute)
{
adapter = new MyRequiredAttributeAdaptor((RequiredAttribute) attribute, stringLocalizer);
}
else if (attribute is EmailAddressAttribute)
{
attribute.ErrorMessage = "Invalid Email Address.";
adapter = base.GetAttributeAdapter(attribute, stringLocalizer);
}
else if (attribute is CompareAttribute)
{
attribute.ErrorMessageResourceName = "InvalidCompare";
attribute.ErrorMessageResourceType = typeof(Resources.ValidationMessages);
var theNewattribute = attribute as CompareAttribute;
adapter = new CompareAttributeAdapter(theNewattribute, stringLocalizer);
}
else
{
adapter = base.GetAttributeAdapter(attribute, stringLocalizer);
}
return adapter;
}
}
2- Add the CustomValidationAttributeAdapterProvider to start up:
Add the following line to public void ConfigureServices(IServiceCollection services) in Startup.cs:
services.AddSingleton <IValidationAttributeAdapterProvider, CustomValidationAttributeAdapterProvider> ();
Here is MyRequiredAttributeAdaptor adaptor:
using System;
using System.ComponentModel.DataAnnotations;
using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;
using Microsoft.Extensions.Localization;
using Microsoft.AspNetCore.Mvc.DataAnnotations.Internal;
public class MyRequiredAttributeAdaptor : AttributeAdapterBase<RequiredAttribute>
{
public MyRequiredAttributeAdaptor(RequiredAttribute attribute, IStringLocalizer stringLocalizer)
: base(attribute, stringLocalizer)
{
}
public override void AddValidation(ClientModelValidationContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
MergeAttribute(context.Attributes, "data-val", "true");
MergeAttribute(context.Attributes, "data-val-required", GetErrorMessage(context));
}
/// <inheritdoc />
public override string GetErrorMessage(ModelValidationContextBase validationContext)
{
if (validationContext == null)
{
throw new ArgumentNullException(nameof(validationContext));
}
return GetErrorMessage(validationContext.ModelMetadata, validationContext.ModelMetadata.GetDisplayName());
}
}
References:
1- See the example of Microsoft: Entropy project: This is a great sample for diffrent features of .NET Core. In this question: see the MinLengthSixAttribute implementation in the Mvc.LocalizationSample.Web sample:
https://github.com/aspnet/Entropy/tree/dev/samples/Mvc.LocalizationSample.Web
2- In order to see how the attribute adapters works see asp.Microsoft.AspNetCore.Mvc.DataAnnotations on github:
https://github.com/aspnet/Mvc/tree/master/src/Microsoft.AspNetCore.Mvc.DataAnnotations
To define a custom validator by a annotation you can define your own class that derives from ValidationAttribute and override the IsValid method. There is no need to register this class explicitly.
In this example a custom validation attribute is used to accept only odd numbers as valid values.
public class MyModel
{
[OddNumber]
public int Number { get; set; }
}
public class OddNumberAttribute : ValidationAttribute
{
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
try
{
var number = (int) value;
if (number % 2 == 1)
return ValidationResult.Success;
else
return new ValidationResult("Only odd numbers are valid.");
}
catch (Exception)
{
return new ValidationResult("Not a number.");
}
}
}
A second approach is that the Model class implements IValidatableObject. This is especially useful, if validation requires access to multiple members of the model class. Here is the second version of the odd number validator:
public class MyModel : IValidatableObject
{
public int Number { get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
if (Number % 2 == 0)
yield return new ValidationResult(
"Only odd numbers are valid.",
new [] {"Number"});
}
}
You can find more information about custom validation in https://docs.asp.net/en/latest/mvc/models/validation.html#custom-validation.
I have a simple controller with a parameter-less Get and a Get that takes in an id.
public class BooksController : ApiController
{
public IEnumerable<string> Get()
{
return new string[] { "value1", "value2" };
}
public string Get(Identity id)
{
return "value";
}
}
Identity is a custom struct that, simplified, looks like this:
public struct Identity
{
// ....
public Identity(Guid value)
{
internalValue = value;
}
}
However, I receive an error stating that multiple actions were found that match the request if I attempt to navigate to either endpoint. The BooksController works just fine if the Get for a single resource takes in a Guid rather than my Identity struct.
My custom model binder and wire-up:
public class IdentityModelBinder : IModelBinder
{
public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
{
Identity identity = new Identity(Guid.Parse(bindingContext.ValueProvider.GetValue(bindingContext.ModelName).AttemptedValue));
bindingContext.Model = identity;
return true;
}
}
GlobalConfiguration.Configuration.BindParameter(typeof(Identity), new IdentityModelBinder());
Note, the above binds fine if any parameters are added to the parameter-less Get. That is, if I change my BooksController to:
public class BooksController : ApiController
{
public IEnumerable<string> Get(int page, string searchTerm)
{
return new string[] { "value1", "value2" };
}
public string Get(Identity id)
{
return "value";
}
}
My route configuration is just the out of the box example:
public static void Register(HttpConfiguration config)
{
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
}
Then I can correctly navigate to both endpoints. How do I go about setting up my BooksController to allow both the parameter-less Get and a Get that takes in my custom Identity?
I think I've found the source of my troubles and I don't see a way around it.
Within the Web API ApiControllerActionSelector, specifically in the ActionCacheSelectorItem.ctor, the logic for resolving action parameters is:
_actionParameterNames.Add(
actionDescriptor,
actionBinding.ParameterBindings
.Where(binding => !binding.Descriptor.IsOptional && TypeHelper.IsSimpleUnderlyingType(binding.Descriptor.ParameterType) && binding.WillReadUri())
.Select(binding => binding.Descriptor.Prefix ?? binding.Descriptor.ParameterName).ToArray());
Unfortunately, this means that only simple types (primitive, datetime, guid, etc) will be included in the parameter list. I can get my struct to show up in the parameter list if I extend the filter logic above to also consider if the parameter can be converted from a string like so:
_actionParameterNames.Add(
actionDescriptor,
actionBinding.ParameterBindings
.Where(binding => !binding.Descriptor.IsOptional &&
(TypeHelper.IsSimpleUnderlyingType(binding.Descriptor.ParameterType) ||
TypeHelper.HasStringConverter(binding.Descriptor.ParameterType)) &&
binding.WillReadUri())
.Select(binding => binding.Descriptor.Prefix ?? binding.Descriptor.ParameterName).ToArray());
I am hoping I'm wrong. Will come back and mark this as the answer after the cooldown period if it turns out I'm stuck.