Pass parameter to Partial View in ASP.NET Core - asp.net-core

Question

On an ASP.NET Core 2.0 application I need to render a partial view and pass a few parameters:
#Html.Partial("Form", new { File = "file.pdf" })
On the partial view I tried to access it using:
#Model.File
And I get the error:
RuntimeBinderException: 'object' does not contain a definition for 'File'
If I simply use on my partial:
#Model
I get the following printed on the page:
{ File = file.pdf }
So there the model is being passed and there is a property File in it.
So what am I missing?

Answer 1

You are passing untyped (anonymous type) data to partial view. You cannot use #Model.File. Instead, you will need to use ViewData's Eval method to retrieve the value.
#ViewData.Eval("File")
Traditional approach is to create a strongly typed ViewModel class, and pass it to the partial view. Then you can access it as #Model.File.
public class SampleViewModel
{
public string File { get; set; }
}
#Html.Partial("Form", new SampleViewModel { File = "file.pdf" })
Inside Partial View,
#model SampleViewModel
<h1>#Model.File</h1>

Answer 2

You should have dynamic as the model of your partial view, this way, you can pass everything - like your anonymous object - and it will just work. Add:
#model dynamic
To the Form.cshtml file.

Answer 3

When you do new { File = "file.pdf" }, you are passing an object that contains an attribute file. Since this is of type object, you can't access any of its variables in c# directly. There some ugly codes to access a fields from an object such as the one that can be found here: C# .NET CORE how to get the value of a custom attribute?
However in this case the most recommended way (for safety) is the create a class and pass an object of that class.
So if you create the following class:
public class MyFileInfo{
public string File { get; set }
}
Then you can create your object by passing:
#Html.Partial("Form", new MyFileInfo{ File = "file.pdf" })
In your partial view, at the beginning, define your model class
#model MyFileInfo
Then in the same file you will now be able to access
#Model.File

Answer 4

For the sake of completeness: you can pass arbitrary variable via a ViewDictionary
#Html.Partial("_Partial", model, new ViewDataDictionary(ViewData) { { "MyVarName", someValue } })
And then access it like this in the partial:
ViewData["MyVarName"]
Another option, you can simply set a ViewData var before calling the partial, and it will be passed on to it
#{
ViewData["MyVarName"] = "hello";
}
#Html.Partial("_Partial", model)
However, strongly typed models are much easier to work with.