OnActionExecuting actionContext binding bool parameter turned string

Question

I have an ActionFilterAttribute where I expect a ViewModel with one of its paramaters as a string.

I read it in the "OnActionExecuting(HttpActionContext actionContext)" method.

As a test, I am sending this parameter as a boolean value: true (instead of a string and without quotes), but the framework is automatically transforming this true boolean into "true" as a string.

Is there a way I can validate that this input parameter is a true or a "true"?

Answer 1

So if I understand correctly I think what you actually want is a custom model binder.

public class NoBooleanModelBinder : IModelBinder
{
    public bool BindModel(
        HttpActionContext actionContext,
        ModelBindingContext bindingContext)
    {
        if (bindingContext.ModelType != typeof(string))
        {
            return false; //we only want this to handle string models
        }

        //get the value that was parsed
        string modelValue = bindingContext.ValueProvider
            .GetValue(bindingContext.ModelName)
            .AttemptedValue;

        //check if that value was "true" or "false", ignoring case.
        if (modelValue.Equals(bool.TrueString, StringComparison.OrdinalIgnoreCase) ||
            modelValue.Equals(bool.FalseString, StringComparison.OrdinalIgnoreCase))
        {
            //add a model error.
            bindingContext.ModelState.AddModelError(bindingContext.ModelName,
                "Values true/false are not accepted");

            //set the value that will be parsed to the controller to null
            bindingContext.Model = null;
        }
        else
        {
            //else everything was okay so set the value.
            bindingContext.Model = modelValue;
        }

        //returning true just means that our model binder did its job
        //so no need to try another model binder.
        return true;
    }
}

Then you might do something like this in your Controller:

public object Post([ModelBinder(typeof(NoBooleanModelBinder))]string somevalue)
{
    if(this.ModelState.IsValid) { ... }
}