ASP.Net MVC Multiple Drop Downs, Single List, Only Allow Unique Selections

Question

I am creating an ASP.Net MVC 4 site where I have a controller with a create action.

The Create action provides a View with several dropdowns each of which I want to bind to a single list of entities from my database.

However, I want to ensure that the selections in each drop down are unique.

How would I go about doing this? Do I need to do some sort of AJAX postback to the server each time a selection is made to somehow update the available options on each of the other drop downs? Or is there a simpler way?

Thanks very much,

Martyn Jones.

well if you want to avoid errors "before validation", than you'll have to use Ajax (your scenario) or (maybe easier) jQuery : event on each dropDown change, removing options with same value as the selected one on all other dropDown. By the way I would add "server-side" validation before saving to db. — Raphaël Althaus
– Raphaël Althaus, Commented Mar 21, 2013 at 16:49
@RaphaëlAlthaus Thank you very much. When you say server side validation, would you just carry that out in the controller actions before saving to the database, or is there a way of applying the constraints I want at the model level? Thanks again! — MartynJones87
– MartynJones87, Commented Mar 21, 2013 at 18:21
Well, if I were you (but I'm not), I would take a look at FluentValidation (fluentvalidation.codeplex.com), really nice for readable and wide validation rules — Raphaël Althaus
– Raphaël Althaus, Commented Mar 21, 2013 at 18:23
@RaphaëlAlthaus That looks like exactly the sort of thing I was looking for. Thanks very much! — MartynJones87
– MartynJones87, Commented Mar 21, 2013 at 18:31

swapneel · Accepted Answer · 2013-03-21 16:53:55Z

0

In your model you can have individual Id fields for each Dropdown. something as below

<%: Html.DropDownListFor(model => model.DropwdownId1,Model.DropdownEntities) %>
<%: Html.DropDownListFor(model => model.DropwdownId2,Model.DropdownEntities) %>
<%: Html.DropDownListFor(model => model.DropwdownId3,Model.DropdownEntities) %>

where Dropdownentities will just return entities from database.

you shall be able to see selected values for each dropdown in Post Action. DropwdownId1 , DropwdownId2

answered Mar 21, 2013 at 16:53

swapneel

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2 Comments

MartynJones87 Over a year ago

Thanks for your answer. Would the fact that each dropdown was using a single source, prevent the same selection being made in multiple dropdowns?

swapneel Over a year ago

No it will not. selection will be saved in ID. you could have same selection across multiple doropdowns or multiple selection across multiple dropdowns

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