razor pages, how to passing json serialized string into model property

Question

I have a model with string property serialized in json format, but i can't save:

public class Foo
{        
    public string NameProp;
    public string JsonCover;
}

public class Cover
{        
    public bool Loop;
    public bool FreeMode;
}

JsonCover string is like this:

{"Loop":true,"FreeMode":true}

View cshtml:

    @model MyLocalPath.Models.Foo
    @using Newtonsoft.Json
    @{Cover cover = JsonConvert.DeserializeObject<Cover>(Model.JsonCover); }

  <div class="row">
    <div class="col-md-4">
        <form method="post">                
            <div class="form-group">
                <label asp-for="@Model.nameProp" class="control-label"></label>
                <input asp-for="@Model.nameProp" class="form-control" />
                <span asp-validation-for="@Model.nameProp"></span>
            </div>                                
            <div class="form-group">
                <label asp-for="@cover.Loop" class="control-label"></label>
                <input asp-for="@cover.Loop" class="form-control" />
                <span asp-validation-for="@cover.Loop"></span>
            </div>
            <div class="form-group">
                <label asp-for="@cover.FreeMode" class="control-label"></label>
                <input asp-for="@cover.FreeMode" class="form-control" />
                <span asp-validation-for="@cover.FreeMode"></span>
            </div>
            <div class="form-group">
                <input type="submit" value="Save" name="save" />
            </div>
        </form>
    </div>
</div>

My problem is In HttpPost IActionResult: Foo.JsonCover is NULL. So I can't save.

Answer 1

You can use custom model binder . According to your requirement , you can create property binder like :

public class CustomModelBinder : IModelBinder
{
    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);

        var loop = bindingContext.HttpContext.Request.Form["cover.loop"][0];
        var freeMode = bindingContext.HttpContext.Request.Form["cover.freemode"][0];

        Cover cover = new Cover() {Loop=Convert.ToBoolean(loop),FreeMode= Convert.ToBoolean(freeMode) };
        var result= JsonConvert.SerializeObject(cover);

        bindingContext.Result = ModelBindingResult.Success(result);

        return Task.CompletedTask;
    }
}

And apply to your model :

public class Foo
{
    public string nameProp { get; set; }

    [BindProperty(BinderType = typeof(CustomModelBinder))]
    public string JsonCover { get; set; }
}

Server side function :

public IActionResult actionName(Foo myViewModel)
{
   ...
}