Multiple model parameters in action - asp.net-mvc

Question

I have an action that will be called with optional querystring parameters. These parameters however are contained in different view models. When I try and add these models to my list of parameters, only a single one is filled and the others are always null. With the exception of an empty query string, where all models are instantiated with defaults.
It is not an option to nest these models for the reason that I don't want the nested property name to be visible in the querystring. So unless that can be circumvented somehow, that would also be a viable solution.
I noticed that, when creating a quick override of the DefaultModelBuilder, all models are parsed but the end result is still that only one model is actually assigned.
This is my scenario:
public ActionResult Index(ModelA ma, ModelB ba)
{
return Content("ok");
}
public class ModelA
{
public string Test { get; set; }
public string Name { get; set; }
}
public class ModelB
{
public int? SomeInteger { get; set; }
public int? TestInteger { get; set; }
}
Desired querystring:
index?Test=Hi&SomeInteger=7
What I want to avoid:
index?ModelA.Test=Hi&ModelB.SomeInteger=7

Answer 1

You can try to make a class combining those two:
public class ModelPair
{
public ModelA A { get; set; }
public ModelB B { get; set; }
}
And then with
public ActionResult Index(ModelPair mp)
{
return Content("ok");
}
You can do ?A.Test=blah&B.SomeInteger=42

Answer 2

I ended up delving in to creating my own custom model binder that does recursive binding. So long as property names are not re-used, which is not a thing that will happen in my models anyway, this fixes my issue of not exposing the property names of the nested model classes.
So now I have the following class structure:
public class ModelA
{
public string Test { get; set; }
public string Name { get; set; }
}
public class ModelB
{
public int? SomeInteger { get; set; }
public int? TestInteger { get; set; }
}
public class ViewModel
{
public ModelA ModelA { get; set; }
public ModelB ModelB { get; set; }
}
And the action now looks like this
public ActionResult Index(ViewModel model)
{
return Content("ok");
}
Which will let me use the following querystring without exposing the ugly property names:
index?Test=Hi&SomeInteger=7&Name=Yep&TestInteger=72
Of course I haven't tested this for an extensive period yet so I have no idea what problems lurk around the corner, but all of the nested models are now properly filled with the data from the querystring and the model classes can be easily re-used : )
public class RecursiveModelBinder : DefaultModelBinder
{
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var model = base.BindModel(controllerContext, bindingContext);
if (model != null)
{
var properties = bindingContext.ModelType.GetProperties().Where(x => x.PropertyType.IsClass && !x.PropertyType.Equals(typeof(string)) );
foreach(var property in properties)
{
var resursiveBindingContext = new ModelBindingContext(bindingContext)
{
ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(null, property.PropertyType)
};
var recursiveModel = BindModel(controllerContext, resursiveBindingContext);
property.SetValue(model, recursiveModel);
}
}
return model;
}
}

Answer 3

As far as I know, the Default Model Binder cannot do that. we have to implement custom Model Binder as follow.
public class CustomModelBinder : IModelBinder
{
public Task BindModelAsync(ModelBindingContext bindingContext)
{
var query = bindingContext.HttpContext.Request.Query;
var modelb = new ModelB();
if (query.TryGetValue($"{bindingContext.ModelName}.{nameof(modelb.SomeInteger)}", out var someInteger))
{
modelb.SomeInteger = Convert.ToInt32(JsonConvert.DeserializeObject(someInteger).ToString());
}
if (query.TryGetValue($"{bindingContext.ModelName}.{nameof(modelb.TestInteger)}", out var testInteger))
{
modelb.TestInteger = Convert.ToInt32(JsonConvert.DeserializeObject(testInteger).ToString());
}
bindingContext.Result = ModelBindingResult.Success(modelb);
return Task.FromResult(modelb);
}
}
In the controller Action we can use Binder as follow
public IActionResult Index(ModelA modelA, [ModelBinder(typeof(CustomModelBinder))]ModelB modelB)
{
return Json(new {modelA, modelB});
}
And in querystring we can have prefix to differentiate each model.
?modelA.test="MATests"&modelA.Name="modelANameValue"&modelB.SomeInteger="5"
Please find working sample here on github