CODEWITHSUNDEEP
asp.net-mvcmodel-view-controllercheckbox
Ari
Ari

Reputation: 3127

Both true and false got from checkbox if it is checked

In my MVC view I have a form with method GET. In that form I have several fields which works fine. After adding a checkbox I found strange behavior. If that checkbox is unchecked I have myCheckbox=false in GET parameter, but when I check the checkbox I have myCheckbox=true&myCheckbox=false.

My view:

...
@using (Html.BeginForm("MyAction", "MyController", FormMethod.Get)) { 
<fieldset>
    SomeInput: @Html.TextBox("someInput") <br />
    ...
    MyCheckbox: @Html.CheckBox("myCheckbox") <br />
</fieldset>
}
...

With value data in SomeInput and unchecked checkbox I'm getting url:

...?someInput=data&myCheckbox=false

and with checked checkbox I'm getting:

...?someInput=data&myCheckbox=true&myCheckbox=false

Upvotes: 0

Views: 865

Answers (1)

Matteo Mosca
Matteo Mosca

Reputation: 7448

That's normal behaviour.

Standard html forms do not send a checkbox unless it is checked. This would lead to a missing parameter in your querystring if the box is not checked.

The html helper generates an input type=hidden for each input type=checkbox that you ask for (and you would have noted this if you took a little time to check the generated html). This is done to ensure that the field is passed down whether it is checked or not. So in the "not checked" scenario the actual checkbox is ignored, and you only have the value from the hidden field:

myField=false

If the checkbox is checked both are passed down, with the same name:

myField=true&myField=false

If I remember correctly if you declare in the receiving actionmethod a parameters bool myField the default ModelBinder takes care of this particular scenario and will net you true when the checkbox is checked and false when it is not.

Upvotes: 1

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