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Is it possible to pass an array of integers to the ASP.NET Web API?


I need to pass an array of integers to an ASP.NET Web API (version 4) REST service.

Here’s how I go about taking action:

public IEnumerable<Category> GetCategories(int[] categoryIds){
// code to retrieve categories from database

And this is the URL that I tried:


Asked by Hemanshu Bhojak

Solution #1

You only need to add [FromUri] before the parameter, as shown below:

GetCategories([FromUri] int[] categoryIds)

And send request:


Answered by Lavel

Solution #2

As Filip W suggests, you may need to use a custom model binder like this (adjusted to bind to the actual type of parameter):

public IEnumerable<Category> 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 => { return converter.ConvertFromString(x != null ? x.Trim() : x); });

                var typedValues = Array.CreateInstance(elementType, values.Length);

                values.CopyTo(typedValues, 0);

                bindingContext.Model = typedValues;
                // change this line to null if you prefer nulls to empty arrays 
                bindingContext.Model = Array.CreateInstance(bindingContext.ModelType.GetElementType(), 0);
            return true;
        return false;

Then you can say something like:

ASP.NET Web API will appropriately bind your categoryIds array when you visit /Categories?categoryids=1,2,3,4.

Answered by Mrchief

Solution #3

I recently encountered this requirement and decided to develop an ActionFilter to address it.

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’m using it like this (notice that I used ‘id’ rather than ‘ids’ because that’s how my route specifies it):

[ArrayInput("id", Separator = ';')]
public IEnumerable<Measure> Get(int[] id)
    return id.Select(i => GetData(i));

And here’s the public url:


This may need to be refactored to match your individual requirements.

Answered by Steve Czetty

Solution #4

If someone needs to do the same or comparable operation (like remove) via POST instead of FromUri, use FromBody and format param as $.param(“: categoryids, true) on the client side (JS/jQuery).


public IHttpActionResult Remove([FromBody] int[] categoryIds)


        type: 'POST',
        data: $.param({ '': categoryids }, true),
        url: url,

The problem with $.param(“: categoryids, true) is expects the post body to have urlencoded values like =1&=2&=3 without the parameter name or brackets.

Answered by Sofija

Solution #5

A simple method for sending array parameters to a web API.


public IEnumerable<Category> GetCategories([FromUri]int[] categoryIds){
 // code to retrieve categories from database

Jquery: as request parameters, send a JSON object

//success response

It will generate your request URL like ../api/categories/GetCategories?categoryIds=1&categoryIds=2&categoryIds=3&categoryIds=4

Answered by Jignesh Variya

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