Multiple forms on an asp.net core 2.2+ web application

Question

Can someone explain the following unexpected behaviour. I've tested this in both core 2.2 and 3.1.

I'm trying to make sense of posting 2 different forms on the same razor page.

Here's the HTML:

<form method="post">
    <button type="submit">post</button>
</form>

<form method="post">
    <button type="submit" asp-page-handler="WTF" >post wtf</button>
</form>

Here's the razor page behind:

public void OnGet()
{
    Debug.WriteLine("Get");
}

public void OnPost()
{
    Debug.WriteLine("Post");
}

public void OnPostWTF()
{
    Debug.WriteLine("PostWTF");
}

I expect that when I press the 'post' button, the OnPost action gets called. When I press the 'post wtf' button, the OnPostWTF action gets called. That kind of happens. If I press the 'post' button initially, the expected action is called. But, as soon as I press the 'post wtf' button, ALL subsequent posts only call the OnPostWTF action, regardless which button is pressed!

Answer 1

Very nice guide here: https://www.learnrazorpages.com/razor-pages/handler-methods

The name of the handler is added to the form's action as a query string parameter.

So when you are posting without a handler then the current url is being posted to.

In your case it will be the one you have switched to with the query parameter handler=WTF .

The best practice when you have multiple forms in the same page, is to setup a handler for each request to avoid such troubles.