I often have screens that have multiple submit buttons on a single form that require a post back. I needed to pass the button value to the controller in MVC. For instance, I may have a data entry screen where a user can click a button that says “Save” or “Save as New”. I need to be able to detect which button they clicked when the page posts back.
Fortunately, there is an easy way to tell, or determine, which button the user selected when the page posts back on a submit action.
First, you need to have a button setup like so:
<form id="rvWidgetForm" method="post" enctype="application/x-www-form-urlencoded" asp-controller="Search" asp-action="SearchBegin">
<button id="btnTopTen" type="submit" name="submitButton" class="btn text-center" value="TopTen">
TOP 10 SEARCH
</button>
<button id="btnTraditional" type="submit" name="submitButton" class="btn text-center" value="Trad">
TRADITIONAL SEARCH
</button>
</form>
The buttons must be of type=submit. Having type=button won’t post back. You have a choice here, to use the value= or not use it. If you don’t declare a value attribute, then what you’ll receive in the controller is the text of the button. While this is okay, you or another developer may change the text in the future and not realize they are going to break your code. I recommend using the value= like I’ve used above. It’s less likely to change in the future.
I recommend using the value attribute as it’s less likely than the button text to change in the future.
The next most important part is the name attribute. Every button that will post back should have the same name. This will be the name of your parameter in your controller as well and they must match. The value you declare on the button will be the argument passed to your controller method.
public async Task<ActionResult> SearchBegin([FromForm] SearchPageModel _searchModelIn, [FromForm] string submitButton)
{
// If you "name" your buttons as "submitButton"
// then you can grab the value of the button
// here to make decisions on which button was clicked
switch (submitButton)
{
case "TopTen":
return TopTen(_searchModelIn);
case "Trad":
return Traditional(_searchModelIn);
default:
break;
}
return View("~/"); // Go home
}
The parameter name in your method must match the name attribute on your buttons exactly. The type passed in will be a string, although I imagine if your value attribute on all your buttons was numeric, that you could declare it as an int.
Once you’re in your method, you can use logic in a switch statement to detect the value passed in and make a decision how to proceed.
