Get property name in Tag Helper - asp.net-mvc

Question

ASP.NET Core introduced custom tag helpers which can be used in views like this:
<country-select value="CountryCode" />
However, I don't understand how can I get model property name in my classes:
public class CountrySelectTagHelper : TagHelper
{
[HtmlAttributeName("value")]
public string Value { get; set; }
public override void Process(TagHelperContext context, TagHelperOutput output)
{
...
// Should return property name, which is "CountryCode" in the above example
var propertyName = ???();
base.Process(context, output);
}
}
In the previous version I was able to do this by using ModelMetadata:
var metadata = ModelMetadata.FromLambdaExpression(expression, html.ViewData);
var property = metadata.PropertyName; // return "CountryCode"
How can I do the same in the new ASP.NET tag helpers?

Answer 1

In order to get property name, you should use ModelExpression in your class instead:
public class CountrySelectTagHelper : TagHelper
{
public ModelExpression For { get; set; }
public override void Process(TagHelperContext context, TagHelperOutput output)
{
var propertyName = For.Metadata.PropertyName;
var value = For.Model as string;
...
base.Process(context, output);
}
}

Answer 2

You can pass a string via the tag helper attribute.
<country-select value="#Model.CountryCode" />
The Value property will be populated by Razor with the value of Model.CountryCode by prepending #. So you get the value directly without the need to pass the name of a model property and accessing that afterwards.

Answer 3

I am not sure whether you got what you wanted. If you are looking to pass the complete model from view to the custom tag helper, this is how i do it.
You can pass in your current model from the view using any custom attributes. See the example below.
Assuming your model is Country
public class Country
{
public string Name { get; set; }
public string Code { get; set; }
}
Now declare a property in your custom tag helper of the same type.
public Country CountryModel { get; set; }
Your controller would look something like this
public IActionResult Index()
{
var country= new Country
{
Name = "United States",
Code = "USA"
};
return View("Generic", country);
}
In this setup, to access your model inside the taghelper, just pass it in like any other custom attribute/property
Your view should now look like something like this
<country-select country-model="#Model"></country-select>
You can receive it in your tag helper like any other class property
public override void Process(TagHelperContext context, TagHelperOutput output)
{
...
// Should return property name, which is "CountryCode" in the above example
var propertyName = CountryModel.Name;
base.Process(context, output);
}
Happy coding!