How to get current model in action filter

Question

I have a generic action filter, and i want to get current model in the OnActionExecuting method. My current implementation is like below:

public class CommandFilter<T> : IActionFilter where T : class, new()
{
    public void OnActionExecuting(ActionExecutingContext actionContext)
    {
        var model= (T)actionContext.ActionArguments["model"];
    }
}

It works well if my all model names are same. But i want to use differnet model names.

How to solve this problem?

Edit

public class HomeController : Controller
{
    [ServiceFilter(typeof(CommandActionFilter<CreateInput>))]
    public IActionResult Create([FromBody]CreateInput model)
    {
        return new OkResult();
    }
}

http://stackoverflow.com/questions/872796/asp-net-mvc-accessing-view-model-from-a-custom-action-filter — user2184057, Aug 11 '16 at 14:11

score 20 · Accepted Answer · edited Oct 25 '18 at 07:40

ActionExecutingContext.ActionArguments is just a dictionary,

    /// <summary>
    /// Gets the arguments to pass when invoking the action. Keys are parameter names.
    /// </summary>
    public virtual IDictionary<string, object> ActionArguments { get; }

And you need to loop through it if you need to avoid hardcoded parameter name ("model"). From the same SO answer for asp.net:

When we create a generic action filter that needs to work on a class of similar objects for some specific requirements, we could have our models implement an interface => know which argument is the model we need to work on and we can call the methods though the interface.

In your case you may write something like this:

public void OnActionExecuting(ActionExecutingContext actionContext)
{
    foreach(var argument in actionContext.ActionArguments.Values.Where(v => v is T))
    {
         T model = argument as T;
         // your logic
    }
}

"is T" then "as T" some way to improve that code ? you are casting twice from my point of view .... — David Noreña, Feb 06 '18 at 01:40
I used `context.ActionArguments.Values.OfType().Single()` as I knew the specific type I wanted — Anttu, Mar 20 '18 at 13:09

Set · Answer 2 · 2016-08-11T13:44:13.527

10

You can use ActionExecutingContext.Controller property

    /// <summary>
    /// Gets the controller instance containing the action.
    /// </summary>
    public virtual object Controller { get; }

and converting result to base MVC Controller get access to model:

((Controller)actionExecutingContext.Controller).ViewData.Model

edited Aug 11 '16 at 13:44

answered Aug 11 '16 at 13:29

Set

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it throws a cast exception : Unable to cast object of type 'MyNamespace.HomeController' to type 'Microsoft.AspNetCore.Mvc.Controller'. – adem caglin Aug 11 '16 at 13:41
oo sorry, i have forgotten `Controller` base definition. I edited code but now model is null(maybe i miss anything). see my update. – adem caglin Aug 11 '16 at 13:52
now I see - you want to get request model, not view model. I have posted another answer – Set Aug 11 '16 at 14:12

score 2 · Answer 3 · edited May 10 '18 at 16:18

2

In case your controller action has multiple arguments and in your filter you want to select the one that is bound via [FromBody], then you can use reflection to do the following:

public void OnActionExecuting(ActionExecutingContext context)
{
    foreach (ControllerParameterDescriptor param in context.ActionDescriptor.Parameters) {
        if (param.ParameterInfo.CustomAttributes.Any(
            attr => attr.AttributeType == typeof(FromBodyAttribute))
        ) {             
            var entity = context.ActionArguments[param.Name];

            // do something with your entity...

edited May 10 '18 at 16:18

Community

1
1

answered Mar 17 '18 at 20:15

Felix K.

14,171
9
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Will I get `given key 'model' was not found in dictionary` if my model was not deserialized correctly? – Azimuth Feb 18 '20 at 14:58
I am lacking the CustomAttributes method in ParameterInfo. Is there any other way to access the custom attributes? – Martin May 20 '22 at 14:13

How to get current model in action filter

3 Answers3

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