passing boolean data into a partial view and using it to conditionally display a class

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Paul 18 posts 159 karma points

Nov 17, 2017 @ 11:46

Hi all, many thanks in advance for your help.

In my template view:

@Html.Partial("HeaderSearchForm", new ViewDataDictionary {{"isExpandable", true}})

In my HeaderSearchForm.cshtml

@{
    var isExpandableValue = (bool)ViewData["isExpandable"];
    var isExpandable = (isExpandableValue) ? "-form expandable-search" : "";
}

I'm getting a nullreference error on line 5

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 


Line 3:  @{
Line 4:      var thing = (bool)ViewData["isExpandable"];
Line 5:      var isExpandable = (thing) ? "-form expandable-search" : "";
Line 6:  }
Line 7:  

Source File: c:\inetpub\wwwroot\mhshomes\Views\Partials\HeaderSearchForm.cshtml    Line: 5

Here's the html for reference:

<form class="[email protected](isExpandable)" role="search" method="POST" action="/Handlers/SiteSearch.ashx">
    <input type="text" value=" " class="search-input" name="search-box" placeholder="Search...">
    <input type="hidden" id="current-node-id" name="current-node-id" value="@Model.Content.Id" />
    <button type="submit" class="search-submit"><i class="fa fa-search"></i></button>
</form>

Currently migrating the platform to MVC views, learning Umbraco and seeing the end of the tunnel. Exciting times.

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Dan Diplo 1554 posts 6205 karma points MVP 6x c-trib

Nov 17, 2017 @ 13:20

0

What does your HeaderSearchForm partial inherit from? It needs to inherit from UmbracoTemplatePage for ViewData to be available, I believe.

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Paul 18 posts 159 karma points

Nov 17, 2017 @ 16:23
0
Thanks for your reply Dan,

I do have this at the top of the file
```
@inherits Umbraco.Web.Mvc.UmbracoTemplatePage
```
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Dan Diplo 1554 posts 6205 karma points MVP 6x c-trib

Nov 17, 2017 @ 16:39
1
Strange, then it should work, assuming you haven't made any typos. I can't see any reason for it not working!

But you could try an alternative approach of passing a model to your partial view that has one boolean field. It's a little neater, but requires a bit more code. So you'd need to create a class, similar to:
```
public class SearchConfigModel
{
    public bool IsExpandable { get; set; }
}
```
Then pass it to your partial:
```
@Html.Partial("HeaderSearchForm", new SearchConfigModel() { IsExpandable = true } })
```
Then make your partial inherit from UmbracoViewPage:
```
@inherits UmbracoViewPage<SearchConfig>
```
You can then access Model.IsExpendable in your partial view.
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Frans Lammers 57 posts 400 karma points c-trib

Jun 19, 2019 @ 12:28
0
A belated answer, but I got the same problem and found the answer. I thought I'd share it here.

The default call to a partial:
```
@Html.Partial("HeaderSearchForm")
```
passes the current model to the partial. You used:
```
@Html.Partial("HeaderSearchForm", new ViewDataDictionary {{"isExpandable", true}})
```
This however does not pass the model, only the ViewDataDictionary. So to pass them both you need to use a different overload of Html.Partial:
```
@Html.Partial("HeaderSearchForm", Model, new ViewDataDictionary {{"isExpandable", true}})
```
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