passing parameters to my partial view? - asp.net-mvc

Question

I am calling my partial view like this:
<% Html.RenderPartial("~/controls/users.ascx"); %>
Can I pass parameters to partial view? How will I access them in the actual users.ascx page?

Answer 1

You could pass a model object to the partial (for example a list of strings):
<% Html.RenderPartial("~/controls/users.ascx", new string[] { "foo", "bar" }); %>
Then you strongly type the partial and the Model property will be of the appropriate type:
<%# Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<System.Collections.Generic.IEnumerable<string>>" %>
<% foreach (var item in Model) { %>
<div><%= Html.Encode(item) %></div>
<% } %>

Answer 2

There is another overload for RenderPartial that will pass your model through.
<% Html.RenderPartial("~/controls/users.ascx", modelGoesHere); %>
How to access? Just like you normally would with any view:
<%= Model.MagicSauce %>

Answer 3

It took a while to sink in, but MVC means you use a Model, a View, and a Controller one way or another for just about everything, including Partial Views. How all three elements fit together can be a little intimidating at first. I'd never done one until just now, and it works --Woohoo!
Hope this helps the next person.... Sorry, I'm using razor instead of .Net forms. I'm also pulling data from a SQL Server database into Entity Framework, which a developer is likely to use. I also probably went a little overboard with WebGrid, which is so much more elegant than a foreach statement. A basic #webgrid.GetHtml() will display every column and row.
Background
In this working example, users have uploaded pictures. Their pictures are displayed in their edit form using a partial view. The ImageID and FileName metadata is persisted in SQL Server while the file itself is persisted in the ~/Content/UserPictures directory.
I know it's kinda half vast, because all the details of uploading and editing personal data isn't shown. Just the germane parts of using a Partial View are focused on, albeit with some bonus EF thrown in. The namespace is MVCApp3 for S&G.
Partial View Model ViewModels.cs
The SQL Server Images table includes many more columns in addition to ImageID and FileName such as [Caption], [Description], a MD5 hash to prevent the same image being uploaded multiple times, and upload date. The ViewModel distills the Entity down to the bare minimum needed for a user to see their pictures.
public class Picts
{
public int ImageID { get; set; }
public string FileName { get; set; }
}
Main View View Edit.cshtml
Note the cast/convert to strongly type the ViewData[].
#Html.Partial(
partialViewName: "Picts",
model: (IEnumerable<MVCApp3.Models.Picts>)ViewData["Picts"]
)
If you don't set the strongly-typed model to use for the Partial View you'll get a "The model item passed into the dictionary is of type 'System.Data.Entity.DynamicProxies..." error because it assumes you're passing the parent/master model.
Partial View View Picts.cshtml (the whole file contents is shown)
#model IEnumerable<MVCApp3.Models.Picts>
#{
var pictsgrid = new WebGrid(Model);
}
#pictsgrid.GetHtml(
tableStyle: "grid",
displayHeader: false,
alternatingRowStyle: "alt",
columns: pictsgrid.Columns(
pictsgrid.Column(format:#<text><img src="#Url.Content("~/Content/Users/" + #item.FileName)" alt="#item.ImageID" width="200" />
#Html.ActionLink(linkText: "Delete", actionName: "DeletePicture", routeValues: new { id = #item.ImageID })
</text>)
))
Controller IdentityController.cs
Set the data content into the ViewData["MyPartialViewModelKeyName"] your partial view will consume. You can give the dictionary key any name you want, but I gave it ViewData["Picts"] to be consistent with the partial view file name and its view model class definition.
Because the pictures may be shared amongst multiple users there is a many-to-many table with a corresponding PITA query in Entity Framework using nested froms and inner joins to return just the pictures belonging to, or shared with, a user:
public class IdentityController : Controller
{
private EzPL8Entities db = new EzPL8Entities();
// GET: /Identity/Edit/5
[Authorize]
public ActionResult Edit(int? id)
{
if (id == null)
return new HttpNotFoundResult("This doesn't exist");
// get main form data
ezpl8_UsersPhysicalIdentity ezIDobj = db.ezpl8_UsersPhysicalIdentity.Find(id)
// http://learnentityframework.com/LearnEntityFramework/tutorials/many-to-many-relationships-in-the-entity-data-model/
// get partial form data for just this user's pictures
ViewData["Picts"] = (from user in db.ezpl8_Users
from ui in user.ezpl8_Images
join image in db.ezpl8_Images
on ui.ImageID equals image.ImageID
where user.ezpl8_UserID == id
select new Picts
{
FileName = image.FileName,
ImageID = image.ImageID
}
).ToList();
return View(ezIDobj);
}
// Here's the Partial View Controller --not much to it!
public ViewResult Picts(int id)
{
return View(ViewData["Picts"]);
}
[Authorize] //you have to at least be logged on
public ActionResult DeletePicture(int id)
{
//ToDo: better security so a user can't delete another user's picture
// TempData["ezpl8_UserID"]
ezpl8_Images i = db.ezpl8_Images.Find(id);
if (i != null)
{
var path = System.IO.Path.Combine(Server.MapPath("~/Content/Users"), i.FileName);
System.IO.File.Delete(path: path);
db.ezpl8_Images.Remove(i);
db.SaveChanges();
}
return Redirect(Request.UrlReferrer.ToString());
}
protected override void Dispose(bool disposing)
{
db.Dispose();
base.Dispose(disposing);
}
}

Answer 4

// get main form data
ezpl8_UsersPhysicalIdentity ezIDobj = db.ezpl8_UsersPhysicalIdentity.Find(id)
// http://learnentityframework.com/LearnEntityFramework/tutorials/many-to-many-relationships-in-the-entity-data-model/
// get partial form data for just this user's pictures
ViewData["Picts"] = (from user in db.ezpl8_Users
from ui in user.ezpl8_Images
join image in db.ezpl8_Images
on ui.ImageID equals image.ImageID
where user.ezpl8_UserID == id
select new Picts
{
FileName = image.FileName,
ImageID = image.ImageID
}
).ToList();
return View(ezIDobj);
}
// Here's the Partial View Controller --not much to it!
public ViewResult Picts(int id)
{
return View(ViewData["Picts"]);
}
[Authorize] //you have to at least be logged on
public ActionResult DeletePicture(int id)
{
//ToDo: better security so a user can't delete another user's picture
// TempData["ezpl8_UserID"]
ezpl8_Images i = db.ezpl8_Images.Find(id);
if (i != null)
{
var path = System.IO.Path.Combine(Server.MapPath("~/Content/Users"), i.FileName);
System.IO.File.Delete(path: path);
db.ezpl8_Images.Remove(i);
db.SaveChanges();
}
return Redirect(Request.UrlReferrer.ToString());
}
protected override void Dispose(bool disposing)
{
db.Dispose();
base.Dispose(disposing);
}
}