Pass an array of integers to ASP NET Web API

Question

I have an ASP NET Web API  version 4  REST service where I need to pass an array of integers   Here is my action method   public IEnumerable lt Category gt  GetCategories int   categoryIds      code to retrieve categories from database     And this is the URL that I have tried    Categories categoryids 1 2 3 4

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ASP NET Core 2 0 Solution  Swagger Ready   Input  DELETE  api items 1 2 DELETE  api items 1   Code  Write the provider  how MVC knows what binder to use   public class CustomBinderProvider   IModelBinderProvider       public IModelBinder GetBinder ModelBinderProviderContext context                if  context    null                        throw new ArgumentNullException nameof context                       if  context Metadata ModelType    typeof int       context Metadata ModelType    typeof List lt int gt                          return new BinderTypeModelBinder typeof CommaDelimitedArrayParameterBinder                       return null            Write the actual binder  access all sorts of info about the request  action  models  types  whatever   public class CommaDelimitedArrayParameterBinder   IModelBinder        public Task BindModelAsync ModelBindingContext bindingContext                 var value   bindingContext ActionContext RouteData Values bindingContext FieldName  as string              Check if the argument value is null or empty         if  string IsNullOrEmpty value                         return Task CompletedTask                     var ints   value  Split      Select int Parse  ToArray             bindingContext Result   ModelBindingResult Success ints            if bindingContext ModelType    typeof List lt int gt                          bindingContext Result   ModelBindingResult Success ints ToList                        return Task CompletedTask            Register it with MVC  services AddMvc options   gt           add custom binder to beginning of collection     options ModelBinderProviders Insert 0  new CustomBinderProvider           Sample usage with a well documented controller for Swagger       lt summary gt      Deletes a list of items       lt  summary gt       lt param name  itemIds  gt The list of unique identifiers for the  items  lt  param gt       lt returns gt The deleted item  lt  returns gt       lt response code  201  gt The item was successfully deleted  lt  response gt       lt response code  400  gt The item is invalid  lt  response gt   HttpDelete   itemIds    Name   ItemControllerRoute DeleteItems    ProducesResponseType typeof void   StatusCodes Status204NoContent    ProducesResponseType typeof void   StatusCodes Status404NotFound   public async Task Delete List lt int gt  itemIds    gt  await  itemAppService RemoveRangeAsync itemIds     EDIT  Microsoft recommends using a TypeConverter for these kids of operations over this approach  So follow the below posters advice and document your custom type with a SchemaFilter

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I have created a custom model binder which converts any comma separated values  only primitive  decimal  float  string  to their corresponding arrays   public class CommaSeparatedToArrayBinder lt T gt    IModelBinder               public bool BindModel HttpActionContext actionContext  ModelBindingContext bindingContext                        Type type   typeof T               if  type IsPrimitive    type    typeof Decimal     type    typeof String     type    typeof float                                 ValueProviderResult val   bindingContext ValueProvider GetValue bindingContext ModelName                   if  val    null  return false                   string key   val RawValue as string                  if  key    null    bindingContext ModelState AddModelError bindingContext ModelName   Wrong value type    return false                     string   values   key Split                       IEnumerable lt T gt  result   this ConvertToDesiredList values  ToArray                    bindingContext Model   result                  return true                             bindingContext ModelState AddModelError bindingContext ModelName   Only primitive  decimal  string and float data types are allowed                   return false                     private IEnumerable lt T gt  ConvertToDesiredArray string   values                        foreach  string value in values                                var val    T Convert ChangeType value  typeof T                    yield return val                                  And how to use in Controller    public IHttpActionResult Get  ModelBinder BinderType   typeof CommaSeparatedToArrayBinder lt int gt     int   ids                        return Ok ids

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In case someone would need - to achieve same or similar thing like delete  via POST instead of FromUri  use FromBody and on client side JS jQuery  format param as   param       categoryids    true   c    public IHttpActionResult Remove  FromBody  int   categoryIds    jQuery     ajax           type   POST           data    param       categoryids    true           url  url              The thing with   param       categoryids    true  is that it  net will expect post body to contain urlencoded value like  1 amp  2 amp  3 without parameter name  and without brackets

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As Filip W points out  you might have to resort to a custom model binder like this  modified to bind to actual type of param      public IEnumerable lt Category gt  GetCategories  ModelBinder typeof CommaDelimitedArrayModelBinder   long   categoryIds            do your thing    public class CommaDelimitedArrayModelBinder   IModelBinder       public bool BindModel HttpActionContext actionContext  ModelBindingContext bindingContext                var key   bindingContext ModelName          var val   bindingContext ValueProvider GetValue key           if  val    null                        var s   val AttemptedValue              if  s    null                                var elementType   bindingContext ModelType GetElementType                    var converter   TypeDescriptor GetConverter elementType                   var values   Array ConvertAll s Split new          StringSplitOptions RemoveEmptyEntries                       x   gt    return converter ConvertFromString x    null   x Trim     x                        var typedValues   Array CreateInstance elementType  values Length                    values CopyTo typedValues  0                    bindingContext Model   typedValues                            else                                  change this line to null if you prefer nulls to empty arrays                  bindingContext Model   Array CreateInstance bindingContext ModelType GetElementType    0                             return true                    return false            And then you can say    Categories categoryids 1 2 3 4 and ASP NET Web API will correctly bind your categoryIds array

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If you want to list  array of integers easiest way to do this is accept the comma    separated list of string and convert it to list of integers Do not forgot to mention  FromUri  attriubte your url look like          ID 71 amp accountID 1 2 3 289 56   public HttpResponseMessage test  FromUri int ID   FromUri string accountID        List lt int gt  accountIdList   new List lt int gt         string   arrAccountId   accountId Split new char                 for  var i   0  i  lt  arrAccountId Length  i                  try                      accountIdList Add Int32 Parse arrAccountId i                       catch  Exception

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Make the method type  HttpPost   create a model that has one int   parameter  and post with json      Model    public class CategoryRequestModel        public int   Categories   get  set          WebApi     HttpPost  public HttpResponseMessage GetCategories CategoryRequestModel model        HttpResponseMessage resp   null       try               var categories     your code to get categories          resp   Request CreateResponse HttpStatusCode OK  categories              catch Exception ex                resp   Request CreateErrorResponse HttpStatusCode InternalServerError  ex              return resp        jQuery    var ajaxSettings         type   POST       url    Categories       data  JSON serialize  Categories   1 2 3 4         contentType   application json       success  function data  textStatus  jqXHR                  get categories from data             ajax ajaxSettings

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I just added the Query key  Refit lib  in the property for the request    Query CollectionFormat Multi    public class ExampleRequest                    FromQuery Name    quot name quot            public string Name   get  set                                    AliasAs  quot category quot             Query CollectionFormat Multi           public List lt string gt  Categories   get  set

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I recently came across this requirement myself  and I decided to implement an ActionFilter to handle this   public class ArrayInputAttribute   ActionFilterAttribute       private readonly string  parameterName       public ArrayInputAttribute string parameterName                 parameterName   parameterName          Separator                   public override void OnActionExecuting HttpActionContext actionContext                if  actionContext ActionArguments ContainsKey  parameterName                         string parameters   string Empty              if  actionContext ControllerContext RouteData Values ContainsKey  parameterName                   parameters    string  actionContext ControllerContext RouteData Values  parameterName               else if  actionContext ControllerContext Request RequestUri ParseQueryString    parameterName     null                  parameters   actionContext ControllerContext Request RequestUri ParseQueryString    parameterName                actionContext ActionArguments  parameterName    parameters Split Separator  Select int Parse  ToArray                         public char Separator   get  set        I am applying it like so  note that I used  id   not  ids   as that is how it is specified in my route     ArrayInput  id   Separator         public IEnumerable lt Measure gt  Get int   id        return id Select i   gt  GetData i        And the public url would be    api Data 1 2 3 4   You may have to refactor this to meet your specific needs

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Instead of using a custom ModelBinder  you can also use a custom type with a TypeConverter    TypeConverter typeof StrListConverter    public class StrList   List lt string gt        public StrList IEnumerable lt string gt  collection    base collection        public class StrListConverter   TypeConverter       public override bool CanConvertFrom ITypeDescriptorContext context  Type sourceType                return sourceType    typeof string     base CanConvertFrom context  sourceType              public override object ConvertFrom ITypeDescriptorContext context  CultureInfo culture  object value                if  value    null              return null           if  value is string s                        if  string IsNullOrEmpty s                   return null              return new StrList s Split                          return base ConvertFrom context  culture  value             The advantage is that it makes the Web API method s parameters very simple  You dont t even need to specify  FromUri    public IEnumerable lt Category gt  GetCategories StrList categoryIds         code to retrieve categories from database     This example is for a List of strings  but you could do categoryIds Select int Parse  or simply write an IntList instead

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I originally used the solution that  Mrchief for years  it works great   But when when I added Swagger to my project for API documentation my end point was NOT showing up   It took me a while  but this is what I came up with  It works with Swagger  and your API method signatures look cleaner   In the end you can do          GET   api values 1 2 3 4        Route  api values  ids         public IHttpActionResult GetIds int   ids                return Ok ids           WebApiConfig cs  public static class WebApiConfig       public static void Register HttpConfiguration config                   Allow WebApi to Use a Custom Parameter Binding         config ParameterBindingRules Add descriptor   gt  descriptor ParameterType    typeof int     amp  amp  descriptor ActionDescriptor SupportedHttpMethods Contains HttpMethod Get                                                               new CommaDelimitedArrayParameterBinder descriptor                                                               null               Allow ApiExplorer to understand this type  Swagger uses ApiExplorer under the hood          TypeDescriptor AddAttributes typeof int     new TypeConverterAttribute typeof StringToIntArrayConverter                 Any existing Code               Create a new class  CommaDelimitedArrayParameterBinder cs  public class CommaDelimitedArrayParameterBinder   HttpParameterBinding  IValueProviderParameterBinding       public CommaDelimitedArrayParameterBinder HttpParameterDescriptor desc            base desc                        lt summary gt          Handles Binding  Converts a comma delimited string into an array of integers           lt  summary gt      public override Task ExecuteBindingAsync ModelMetadataProvider metadataProvider                                               HttpActionContext actionContext                                               CancellationToken cancellationToken                var queryString   actionContext ControllerContext RouteData Values Descriptor ParameterName  as string           var ints   queryString  Split      Select int Parse  ToArray             SetValue actionContext  ints            return Task CompletedTask             public IEnumerable lt ValueProviderFactory gt  ValueProviderFactories   get      new     new QueryStringValueProviderFactory          Create a new class  StringToIntArrayConverter cs  public class StringToIntArrayConverter   TypeConverter       public override bool CanConvertFrom ITypeDescriptorContext context  Type sourceType                return sourceType    typeof string     base CanConvertFrom context  sourceType             Notes     https   stackoverflow com a 47123965 862011 pointed me in the right direction Swagger was only failing to pick my comma delimited end points when using the  Route  attribute

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public class ArrayInputAttribute   ActionFilterAttribute       private readonly string    ParameterNames           lt summary gt                    lt  summary gt      public string Separator   get  set             lt summary gt          cons          lt  summary gt           lt param name  parameterName  gt  lt  param gt      public ArrayInputAttribute params string   parameterName                 ParameterNames   parameterName          Separator                        lt summary gt                    lt  summary gt      public void ProcessArrayInput HttpActionContext actionContext  string parameterName                if  actionContext ActionArguments ContainsKey parameterName                         var parameterDescriptor   actionContext ActionDescriptor GetParameters   FirstOrDefault p   gt  p ParameterName    parameterName               if  parameterDescriptor    null  amp  amp  parameterDescriptor ParameterType IsArray                                var type   parameterDescriptor ParameterType GetElementType                    var parameters   String Empty                  if  actionContext ControllerContext RouteData Values ContainsKey parameterName                                         parameters    string actionContext ControllerContext RouteData Values parameterName                                     else                                       var queryString   actionContext ControllerContext Request RequestUri ParseQueryString                        if  queryString parameterName     null                                                parameters   queryString parameterName                                                            var values   parameters Split new     Separator    StringSplitOptions RemoveEmptyEntries                       Select TypeDescriptor GetConverter type  ConvertFromString  ToArray                    var typedValues   Array CreateInstance type  values Length                   values CopyTo typedValues  0                   actionContext ActionArguments parameterName    typedValues                                     public override void OnActionExecuting HttpActionContext actionContext                 ParameterNames ForEach parameterName   gt  ProcessArrayInput actionContext  parameterName              Usage        HttpDelete       ArrayInput  tagIDs         Route  api v1 files  fileID  tags  tagIDs         public HttpResponseMessage RemoveFileTags Guid fileID  Guid   tagIDs                 FileRepository RemoveFileTags fileID  tagIDs           return Request CreateResponse HttpStatusCode OK           Request uri  http   localhost api v1 files 2a9937c7-8201-59b7-bc8d-11a9178895d0 tags BBA5CD5D-F07D-47A9-8DEE-D19F5FA65F63 BBA5CD5D-F07D-47A9-8DEE-D19F5FA65F63

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Or you could just pass a string of delimited items and put it into an array or list on the receiving end

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I addressed this issue this way   I used a post message to the api to send the list of integers as data   Then I returned the data as an ienumerable   The sending code is as follows   public override IEnumerable lt Contact gt  Fill IEnumerable lt int gt  ids        IEnumerable lt Contact gt  result   null      if  ids  null amp  amp ids Count   gt 0                try                       using  var client   new HttpClient                                  client BaseAddress   new Uri  http   localhost 49520                     client DefaultRequestHeaders Accept Clear                    client DefaultRequestHeaders Accept Add new MediaTypeWithQualityHeaderValue  application json                      String  endPoint    api     typeof Contact  Name     ListArray                    HttpResponseMessage response   client PostAsJsonAsync lt IEnumerable lt int gt  gt   endPoint  ids  Result                  response EnsureSuccessStatusCode                    if  response IsSuccessStatusCode                                        result   JsonConvert DeserializeObject lt IEnumerable lt Contact gt  gt  response Content ReadAsStringAsync   Result                                                       catch  Exception                                 return result      The receiving code is as follows      POST api  lt controller gt   HttpPost   ActionName  ListArray    public IEnumerable lt Contact gt  Post  FromBody IEnumerable lt int gt  ids        IEnumerable lt Contact gt  result   null      if  ids    null  amp  amp  ids Count    gt  0                return contactRepository Fill ids             return result      It works just fine for one record or many records   The fill is an overloaded method using DapperExtensions   public override IEnumerable lt Contact gt  Fill IEnumerable lt int gt  ids        IEnumerable lt Contact gt  result   null      if  ids    null  amp  amp  ids Count    gt  0                using  IDbConnection dbConnection   ConnectionProvider OpenConnection                          dbConnection Open                var predicate   Predicates Field lt Contact gt  f   gt  f id  Operator Eq  ids               result   dbConnection GetList lt Contact gt  predicate               dbConnection Close                        return result      This allows you to fetch data from a composite table  the id list   and then return the records you are really interested in from the target table   You could do the same with a view  but this gives you a little more control and flexibility   In addition  the details of what you are seeking from the database are not shown in the query string   You also do not have to convert from a csv file   You have to keep in mind when using any tool like the web api 2 x interface is that the get  put  post  delete  head  etc   functions have a general use  but are not restricted to that use   So  while post is generally used in a create context in the web api interface  it is not restricted to that use   It is a regular html call that can be used for any purpose permitted by html practice   In addition  the details of what is going on are hidden from those  prying eyes  we hear so much about these days   The flexibility in naming conventions in the web api 2 x interface and use of regular web calling means you send a call to the web api that misleads snoopers into thinking you are really doing something else   You can use  POST  to really retrieve data  for example

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You just need to add  FromUri  before parameter  looks like   GetCategories  FromUri  int   categoryIds    And send request     Categories categoryids 1 amp categoryids 2 amp categoryids 3

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You may try this code for you to take comma separated values   an array of values to get back a JSON from webAPI   public class CategoryController   ApiController         public List lt Category gt  Get String categoryIDs                  List lt Category gt  categoryRepo   new List lt Category gt               String   idRepo   categoryIDs Split                 foreach  var id in idRepo                          categoryRepo Add new Category                                   CategoryID   id                   CategoryName   String Format  Category  0    id                                       return categoryRepo              public class Category         public String CategoryID   get  set         public String CategoryName   get  set          Output        CategoryID   4   CategoryName   Category 4       CategoryID   5   CategoryName   Category 5       CategoryID   3   CategoryName   Category 3

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My solution was to create an attribute to validate strings  it does a bunch of extra common features  including regex validation that you can use to check for numbers only and then later I convert to integers as needed     This is how you use   public class MustBeListAndContainAttribute   ValidationAttribute       private Regex regex   null      public bool RemoveDuplicates   get        public string Separator   get        public int MinimumItems   get        public int MaximumItems   get         public MustBeListAndContainAttribute string regexEachItem          int minimumItems   1          int maximumItems   0          string separator                bool removeDuplicates   false    base                 this MinimumItems   minimumItems          this MaximumItems   maximumItems          this Separator   separator          this RemoveDuplicates   removeDuplicates           if   string IsNullOrEmpty regexEachItem               regex   new Regex regexEachItem  RegexOptions Compiled   RegexOptions Singleline   RegexOptions IgnoreCase              protected override ValidationResult IsValid object value  ValidationContext validationContext                var listOfdValues    value as List lt string gt    0            if  string IsNullOrWhiteSpace listOfdValues                         if  MinimumItems  gt  0                  return new ValidationResult this ErrorMessage               else                 return null                      var list   new List lt string gt              list AddRange listOfdValues Split new     Separator    System StringSplitOptions RemoveEmptyEntries             if  RemoveDuplicates  list   list Distinct   ToList             var prop   validationContext ObjectType GetProperty validationContext MemberName           prop SetValue validationContext ObjectInstance  list           value   list           if  regex    null              if  list Any c   gt  string IsNullOrWhiteSpace c      regex IsMatch c                    return new ValidationResult this ErrorMessage            return null

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Easy way to send array params to web api   API   public IEnumerable lt Category gt  GetCategories  FromUri int   categoryIds       code to retrieve categories from database     Jquery   send JSON object as request params    get  api categories GetCategories   categoryIds  1 2 3 4    done function response   console log response     success response       It will generate your request URL like     api categories GetCategories categoryIds 1 amp categoryIds 2 amp categoryIds 3 amp categoryIds 4

[c#] Pass an array of integers to ASP.NET Web API?

ASP.NET Core 2.0 Solution (Swagger Ready)

Input

Code

Write the provider (how MVC knows what binder to use)

Write the actual binder (access all sorts of info about the request, action, models, types, whatever)

Register it with MVC

Sample usage with a well documented controller for Swagger

Examples related to c#

Examples related to arrays

Examples related to rest

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