TempData used to store temporary data which can be used in the subsequent request by the user. TempData will be cleared out after the completion of a subsequent request.
TempData is useful when you want to transfer non-sensitive data from one action method to another action method of the same or a different controller as well as redirects. It is dictionary type which is derived from TempDictionary.
Adding a key-value pair in TempData as shown in the below example.
Example: TempData
publicclassAventController : Controller
{
// GET: Studentpublic AventController()
{
}
publicActionResult Index()
{
TempData["name"] = "Test data";
TempData["age"] = 30;
return View();
}
publicActionResult About()
{
string userName;
int userAge;
if(TempData.ContainsKey("name"))
userName = TempData["name"].ToString();
if(TempData.ContainsKey("age"))
userAge = int.Parse(TempData["age"].ToString());
// do something with userName or userAge here return View();
}
}
In the above code, we added data into TempData and accessed the same data using a key inside another action method. Notice that we have converted values into the appropriate type.
As you can see in the above example, we add test data in TempData in the first request and in the second subsequent request we access test data from TempData which we stored in the first request. However, you can’t get the same data in the third request because TempData will be cleared out after second request.
Call TempData.Keep() to retain TempData values in a third consecutive request.
In the above example, we have added a student list with the key “students” in the ViewData dictionary. So now, the student list can be accessed in a view as shown below.
ViewData and ViewBag both use the same dictionary internally. So we cannot have ViewData Key matches with the property name of ViewBag, otherwise it will throw a runtime exception.
Example: ViewBag and ViewData
publicActionResult Index()
{
ViewBag.Id = 1;
ViewData.Add("Id", 1); // throw runtime exception as it already has "Id" key
ViewData.Add(newKeyValuePair<string, object>("Name", "Bill"));
ViewData.Add(newKeyValuePair<string, object>("Age", 20));
return View();
}
ViewBag is useful to transfer temporary data (which is not included in model) from the controller to the view. The viewBag is a dynamic type property of ControllerBase class which is the base class of all the controllers.
The following figure illustrates the ViewBag.
In the above figure, it attaches Name property to ViewBag with the dot notation and assigns a string value to “Bill” to it in the controller. This can be accessed in the view like @ViewBag.Name. (@ is razor syntax to access the server side variable.)
You can assign any number of properties and values to ViewBag. If you assign the same property name multiple times to ViewBag, then it will only consider last value assigned to the property.
The following example demonstrates how to transfer data from controller to view using ViewBag.
In the above example, we want to display the total number of students in a view for the demo. So, we have attached the TotalStudents property to the ViewBag and assigned the student count using studentList.Count().
Now, in the Index.cshtml view, you can access ViewBag.TotalStudents property and display all the student info as shown below.
In this section you will learn about partial views in ASP.NET MVC.
What is Partial View?
Partial view is a reusable view, which can be used as a child view in multiple other views. It eliminates duplicate coding by reusing same partial view in multiple places. You can use the partial view in the layout view, as well as other content views.
To start with, let’s create a simple partial view for the following navigation bar for demo purposes. We will create a partial view for it, so that we can use the same navigation bar in multiple layout views without rewriting the same code everywhere.
Partial View
The following figure shows the html code for the above navigation bar. We will cut and paste this code in a seperate partial view for demo purposes.
Partial Views
Create New Partial View:
To create a partial view, right click on Shared folder -> select Add -> click on View..
Note :If a partial view will be shared with multiple views of different controller folder then create it in the Shared folder, otherwise you can create the partial view in the same folder where it is going to be used.
In the Add View dialogue, enter View name and select “Create as a partial view” checkbox and click Add.
Partial Views
We are not going to use any model for this partial view, so keep the Template dropdown as Empty (without model) and click Add. This will create an empty partial view in Shared folder.
Now, you can cut the above code for navigation bar and paste it in _HeaderNavBar.cshtml as shown below:
Partial View: _HeaderNavBar.cshtml
<divclass="navbar navbar-inverse navbar-fixed-top"><divclass="container"><divclass="navbar-header"><buttontype="button"class="navbar-toggle"data-toggle="collapse"data-target=".navbar-collapse"><spanclass="icon-bar"></span><spanclass="icon-bar"></span><spanclass="icon-bar"></span></button>@Html.ActionLink("Application name", "Index", "Home", new { area = "" }, new { @class = "navbar-brand" })
</div><divclass="navbar-collapse collapse"><ulclass="nav navbar-nav"><li>@Html.ActionLink("Home", "Index", "Home")</li>
<li>@Html.ActionLink("About", "About", "Home")</li>
<li>@Html.ActionLink("Contact", "Contact", "Home")</li>
</ul></div></div></div>
Thus, you can create a new partial view. Let’s see how to render partial view.
Render Partial View:
You can render the partial view in the parent view using html helper methods: Partial() or RenderPartial() or RenderAction(). Each method serves different purposes. Let’s have an overview of each method and then see how to render partial view using these methods.
Html.Partial():
@Html.Partial() helper method renders the specified partial view. It accept partial view name as a string parameter and returns MvcHtmlString. It returns html string so you have a chance of modifing the html before rendering.
The following table lists overloads of the Partial helper method:
Renders the partial view content in the referred view. Model parameter passes the model object and View data passes view data dictionary to the partial view.
Html.RenderPartial():
The RenderPartial helper method is same as the Partial method except that it returns void and writes resulted html of a specified partial view into a http response stream directly.
Renders the specified partial view, replacing the partial view’s ViewData property with the specified ViewDataDictionary object and set the specified model object
Html.RenderAction():
The RenderAction helper method invokes a specified controller and action and renders the result as a partial view. The specified Action method should return PartialViewResult using the Partial() method.
Name
Description
RenderAction(String actionName)
Invokes the specified child action method and renders the result in the parent view.
Invokes the specified child action method using the specified parameters and controller name and renders the result inline in the parent view.
So now, we can use any of the above rending methods to render the _HeaderNavBar partial view into _Layout.cshtml. The following layout view renders partial view using the RenderPartial() method.