Why we need to use @using with Html.BeginForm

Question

Can someone explain to me why we need to use

@using (Html.BeginForm("CheckUser", "Home", FormMethod.Post))

Instead of :

@Html.BeginForm("CheckUser", "Home", FormMethod.Post)

What is the main purpose of @using in here, as far as I know, I only use 'using' keyword to make sure that the object is disposed as soon as it goes out of scope. I am a little confused.

I am asking this question because @Html.BeginForm outputs a text : "System.Web.Mvc.Html.MvcForm {" before rendering the content of the form. And by using the 'using' keyword this text is not rendered.

Edit: This is my code that renders the "System.Web.Mvc.Html.MvcForm ..."

@Html.BeginForm("CheckUser", "Home", FormMethod.Post)
    <label for="username">Username :</label>
    <input type="text" name="username" id="username" placeholder="username"/>

    <label for="password">Password :</label>
    <input type="password" name="password" id="password" placeholder="password"/>

    <input type="submit" value="Submit" />
@{Html.EndForm();}

that is to generate corresponding closing tag (in this case the closing <form> tag) — Thangadurai
– Thangadurai, Commented Jan 20, 2017 at 10:00
I am not convinced yet, why we need to use the using keyword ? — Mehdi Souregi
– Mehdi Souregi, Commented Jan 20, 2017 at 10:01
The output of the closing tag is implemented by the dispose method. By not using 'using' you would not have a closing '</form>' tag. — mstaessen
– mstaessen, Commented Jan 20, 2017 at 10:03
Why without using the 'using' keyword the output is "System.Web.Mvc.Html.MvcForm { ..." ? and we also have the closing tag </form> ? — Mehdi Souregi
– Mehdi Souregi, Commented Jan 20, 2017 at 10:21

K D · Accepted Answer · 2017-01-20 10:31:39Z

4

by using @using (Html.BeginForm("CheckUser", "Home", FormMethod.Post))

It automatically adds </form> in your page. you don't need to care about closing your form tag and it prevents accidental issue if somebody forgets to close the form.

@*<form>*@
    @using (Html.BeginForm("CheckUser", "Home", FormMethod.Post)) 
    {

    }@* </form> gets added automaticaly*@

If you want to use Html.EndForm(), use it like following

@{Html.BeginForm("CheckUser", "Home", FormMethod.Post);}
//other form elements
@{Html.EndForm();}

Reason: Html.EndForm() doesn't returns anything( return type void), it write on the stream in stead. If you don't use {}, @ symbol will expect something to return from the following statement hence it will use object.ToString() which results into System.Web.Mvc.Html.MvcForm

edited Jan 20, 2017 at 10:31

answered Jan 20, 2017 at 10:04

K D

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5 Comments

Mehdi Souregi Over a year ago

I used the @Html.EndForm but it still renders "System.Web.Mvc.Html.MvcForm " before rendering the content of the form.

K D Over a year ago

use it like this @{Html.EndForm();}

Mehdi Souregi Over a year ago

yes, i used this form actually @{Html.EndForm();}, the @Html.EndForm did not work for me :) .But it still renders "System.Web.Mvc.Html.MvcForm "

K D Over a year ago

your begin form statement should also be like @{Html.BeginForm(...)} can you paste your html along with these helpers in your question?

K D Over a year ago

yeah, you have not added Begin form correctly. check the usage in my answer again and try

Jamiec · Accepted Answer · 2017-01-20 10:40:32Z

4

BeginForm has a rather interesting (mis)use of the IDisposible pattern!

Starting at the beginning, BeginForm returns an instance of MvcForm. MvcForm implements IDisposible and its Dispose method...

[...] renders the closing tag at the end of a Using statement.

_{(source: https://msdn.microsoft.com/en-us/library/system.web.mvc.html.mvcform.dispose(v=vs.118).aspx#M:System.Web.Mvc.Html.MvcForm.Dispose)}

Without this sort of implementation you would need to do something along the lines of

@{ Html.BeginForm("CheckUser", "Home", FormMethod.Post); }
<!-- form content here -->
@{ Html.EndForm(); }

Which, I guess, they made the decision would be clunky and easy to forget.

edited Jan 20, 2017 at 10:40

user3559349

answered Jan 20, 2017 at 10:04

Jamiec

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3 Comments

Mehdi Souregi Over a year ago

Thanks for the @{Html.EndForm();}, this is first time I hear of about it, But it still renders "System.Web.Mvc.Html.MvcForm { ..."

user3559349 Over a year ago

@Souregi, Both the BeginForm() and EndForm() need to be wrapped in @{ ... } because they return void (Jamiec, I took the liberty of editing your answer to show the correct syntax - and EndForm() does exist :)

Mehdi Souregi Over a year ago

thump up for Stephen Muecke it is clear for me now :)

Patrick Hofman · Accepted Answer · 2017-01-20 10:04:43Z

3

This is a trick to force rendering of the close tags of the form.

The trick is based on the IDisposable interface, which using understands and uses to call the Dispose method after the block has ended.

The Dispose implementation of the type returned from BeginForm actually doesn't dispose anything. It just writes the closing tag to the output stream.

answered Jan 20, 2017 at 10:04

Patrick Hofman

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1 Comment

PhillipH Over a year ago

I agree - its just syntax sugar for knowing what the scope of your form is, in order to close it.

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