Question

I have a class I model bind and I want to use output caching with it. I can’t find a way to access the bound object in GetVaryByCustomString

For example:

public class MyClass
{
    public string Id { get; set; }
    ... More properties here
}

public class MyClassModelBinder : DefaultModelBinder
{
   public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
   {
      var model = new MyClass();
      ... build the class       
      return model;
    }
}

I set the binder in Global.cs

ModelBinders.Binders.Add(typeof(MyClass), new MyClassModelBinder());

And then use output caching like this.

[OutputCache(Duration = 300, VaryByCustom = "myClass")]
public ActionResult MyAction(MyClass myClass)
{
   .......

public override string GetVaryByCustomString(HttpContext context, string custom)
{
   ... check we're working with 'MyClass'

   var routeData = RouteTable.Routes.GetRouteData(new HttpContextWrapper(context));
   var myClass = (MyClass)routeData.Values["myClass"]; <-- This is always null

myClass isn’t in the route table event though the model binder fired.

Any help as always will be most welcome.

Cheers

Answer 1

The model binder doesn’t add the model to the RouteData, so you cannot expect to fetch it from there.

One possibility is to store the model inside the HttpContext inside your custom model binder:

public class MyClassModelBinder : DefaultModelBinder
{
   public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
   {
      var model = new MyClass();
      // ... build the class

      // Store the model inside the HttpContext so that it is accessible later
      controllerContext.HttpContext.Items["model"] = model;
      return model;
    }
}

and then retrieve it inside the GetVaryByCustomString method using the same key (model in my example):

public override string GetVaryByCustomString(HttpContext context, string custom)
{
    var myClass = (MyClass)context.Items["model"];

    ...
}