Model binding comma separated query string parameter

Question

How can I bind query string parameter that is comma separated value

http://localhost/Action?ids=4783,5063,5305

to a controller action expec

Answer 1

Taken from my answer:

I will show you here a very simple custom model binder I have just written (and tested in .Net Core 2.0):

My model binder:

public class CustomModelBinder : IModelBinder
{
    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
        var value = valueProviderResult.FirstValue; // get the value as string

        var model = value?.Split(",");
        bindingContext.Result = ModelBindingResult.Success(model);

        return Task.CompletedTask;
    }
}

My model (and notice, only one property has my custom model binder annotation):

public class CreatePostViewModel
{
    [Display(Name = nameof(ContentText))]
    [MinLength(10, ErrorMessage = ValidationErrors.MinLength)]
    public string ContentText { get; set; }

    [BindProperty(BinderType = typeof(CustomModelBinder))]
    public IEnumerable Categories { get; set; } // <<<<<< THIS IS WHAT YOU ARE INTERESTER IN

    #region View Data
    public string PageTitle { get; set; }
    public string TitlePlaceHolder { get; set; }
    #endregion
}

What it does is: it receives some text like "aaa,bbb,ccc", and converts it into array, and return it to the ViewModel.

I hope that helps.

DISCLAIMER: I am not an expert in model binders writing, I have learn that 15 minutes ago, and I found your question (with no helpful answer), so I tried to help. This is a very basic model binder, some improvements are surely required. I learned how to write it from the official documentation page.