The ASP.NET MVC Razor implementation is closely tied to ASP.NET and MVC and the View template (WebViewPage class) includes a few MVC-specific features as well as back references to the controller. In other words MVC Razor is designed with MVC in mind. With Razor, you can create a custom Razor Engine that can be used in any .NET environment. Razor is the best view engine available for MVC as its much cleaner and easy to write and read. This view engine is compatible with unit testing frameworks. In this article, I will demonstrate how you can render ASP.NET MVC Razor Views in ASP.Net MVC 1.0, 2.0 RC, 3 and 4 .
Basically, all you do is create a fake HttpContext for the view to render itself.  This is an extensions method of the HtmlHelper that processes a partial view through the default MVC view engine and then renders it to the response stream.

Thisworks on ASP.NET MVC 1.0 (changing Headers on the original HttpResponse doesn't throwthe "Server cannot set content type after HTTP headers have been sent"exception).
/// <summary>Renders a view to string.</summary>
public static string RenderViewToString(this Controller controller, string viewName, object viewData) {

Create memory writer.
var sb = new StringBuilder();
var memWriter = new StringWriter(sb);

Create fake http context to render the view.
    var fakeResponse = new HttpResponse(memWriter);
    var fakeContext = new HttpContext(HttpContext.Current.Request, fakeResponse);
    var fakeControllerContext = new ControllerContext(
        new HttpContextWrapper(fakeContext),
        controller.ControllerContext.RouteData,
        controller.ControllerContext.Controller);
    var oldContext = HttpContext.Current;
    HttpContext.Current = fakeContext;
  Use HtmlHelper to render partial view to fake context.
    var html = new HtmlHelper(new ViewContext(fakeControllerContext,
        new FakeView(), new ViewDataDictionary(), new TempDataDictionary()),
        new ViewPage());
    html.RenderPartial(viewName, viewData);
Restore context.
    HttpContext.Current = oldContext;  
    //Flush memory and return output
    memWriter.Flush();
    return sb.ToString();}
Fake IView implementation used to instantiate an HtmlHelper.
public class FakeView : IView {
    #region IView Members
    public void Render(ViewContext viewContext, System.IO.TextWriter writer) {
        throw new NotImplementedException();
    }    #endregion
}

In ASP.NET MVC 2.0 RC, the code changes a bit because we have to pass in the StringWriter used to write the view into the ViewContext:
Use HtmlHelper to render partial view to fake context.

//...
var html = new HtmlHelper(
    new ViewContext(fakeControllerContext, new FakeView(),
        new ViewDataDictionary(), new TempDataDictionary(), memWriter),
    new ViewPage());
html.RenderPartial(viewName, viewData);
//...

In MVC 3 you can used this code :
public static string RazorRender(Controller context, string DefaultAction)
{
string Cache = string.Empty;
System.Text.StringBuilder sb = new System.Text.StringBuilder();
System.IO.TextWriter tw = new System.IO.StringWriter(sb);
RazorView view_ = new RazorView(context.ControllerContext, DefaultAction, null, false, null);
view_.Render(new ViewContext(context.ControllerContext, view_, new ViewDataDictionary(), new TempDataDictionary(), tw), tw);
Cache = sb.ToString();
return Cache;
}
public static string RenderRazorViewToString(string viewName, object model)
        {
ViewData.Model = model;
using (var sw = new StringWriter())
            {
var viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, viewName);
var viewContext = new ViewContext(ControllerContext, viewResult.View, ViewData, TempData, sw);
viewResult.View.Render(viewContext, sw);
return sw.GetStringBuilder().ToString();
}
}
public static class HtmlHelperExtensions
        {
public static string RenderPartialToString(ControllerContext context, string partialViewName, ViewDataDictionary viewData, TempDataDictionary tempData)
            {
ViewEngineResult result = ViewEngines.Engines.FindPartialView(context, partialViewName);
if (result.View != null)
                {
StringBuilder sb = new StringBuilder();
using (StringWriter sw = new StringWriter(sb))
                    {
using (HtmlTextWriter output = new HtmlTextWriter(sw))
                        {
ViewContext viewContext = new ViewContext(context, result.View, viewData, tempData, output);
result.View.Render(viewContext, output);
}
}
return sb.ToString();

}
return String.Empty;
            }
        }

This code worked in MVC 4 :
public string RenderRazorViewToString(string viewName, object model) {
    ViewData.Model = model;
    using (var sw = new StringWriter()) {
        var viewResult = ViewEngines.Engines.FindPartialView(ControllerContext, viewName);
        var viewContext = new ViewContext(ControllerContext, viewResult.View, ViewData, TempData, sw);
        viewResult.View.Render(viewContext, sw);
        viewResult.ViewEngine.ReleaseView(ControllerContext, viewResult.View);
        return sw.GetStringBuilder().ToString();
    }
}

I hope you will enjoy this Article, and I hope you will refer this article for your need. Stay tuned and stay connected for more technical updates with ASPHostPortal

In Asp.Net MVC 5 (Model-View-Controller) there are three options ViewBag, ViewData, and TempData to pass small amount of data from controller to view. In this article i am going to explain what is ViewBag, ViewData and TempData and their use in Asp.Net MVC 5.

A. ViewData & ViewBag objects.
ViewData is a dictionary object that you put data into, which then becomes available to the view.It is an in-built dictionary object that is derived from ViewDataDictionary class that can be accessed and set with string type key values. It is a used to pass data from Controller to View. ViewData's value become null if redirection occur because its life lies only during current request.

Key points to remember about ViewData.

• ViewData is a dictionary of objects that is derived from ViewDataDictionary class and accessible using strings as keys.
• ViewData requires typecasting for complex data type and it is recommended to check for null values to avoid error.
• ViewData is used to pass small amount of data from controller to view, so it helps to maintain data when moving from controller to view.
• ViewData has short life i.e.  Its value becomes null when redirection occurs because its life lies only during current request. This is because the aim of ViewData is to provide a way to transfer/pass data from controllers and views.
• ViewData is faster than ViewBag.

ViewData Example.
In View:
@ViewData["Name"]

ViewBag is dynamic object, meaning we can add properties to it in the controller, and read them later in the view. Its value becomes null when redirection occurs because its life lies only during current request. This is because the aim of ViewBag is to provide a way to transfer/pass data from controllers and views.

ViewBag Example:
In View:
@ViewBag.Name

Similarities between ViewBag & ViewData :
Both the ViewData and ViewBag objects are great for accessing extra data (i.e., outside the data model), between the controller and view. Since views already expect a specific object as their model, this type of data access to extra data, MVC implements it as a property of both views and controllers, making usage and access to these objects easy. Helps to maintain data when you move from controller to view. Used to pass data from controller to corresponding view. Short life means value becomes null when redirection occurs. This is because their goal is to provide a way to communicate between controllers and views. It’s a communication mechanism within the server call.

Difference between ViewBag & ViewData:

• ViewData is a dictionary of objects that is derived from ViewDataDictionary class and accessible using strings as keys.
• ViewBag is a dynamic property that takes advantage of the new dynamic features in C# 4.0.
• ViewData requires typecasting for complex data type and check for null values to avoid error.
• ViewBag doesn’t require typecasting for complex data type.

B. TempData Object.The problem with the ViewData and ViewBag for transferring data from controller to view is that the data is only alive for current request. The data is lost if a redirection takes place i.e. if one Action redirects to another action. But when we need to persist the data between actions/redirection then asp.net MVC offers another dictionary object called TempData for that purpose. It is derived from TempDataDictionary and created on top of session. It will live till the redirected view is fully loaded. “TempData”  Helps to maintain data when you move from one controller to other controller or from one action to other action.The benefit is that if you have a chain of multiple redirections it won’t cause TempData to be emptied the values will still be there until you actually use them, then they clear up after themselves automatically.

When to use TempData in ASP.NET MVC ?
Example condition :
I came across this problem where I had a basic list of items and for each if these items I wanted to add a delete action on my controller. I wanted to add some error checking around the delete action so if someone attempted to modify the URL and enter a incorrect parameter into my controller, I wanted to redirect back to the previous controller and notify the user of this mistake. Take this example. I have a Product Controller and the Index Action and View lists all of the products. I have a delete action on the Product Controller which checks if the productId parameter is valid and then removes the product and redirects to the Index action using the RedirectToAction method.

The solution :
When validating the productId, if its NOT valid simply add a new key/value to the TempData object and call the RedirectToAction method. TempData stores data for short periods of time for the current and next HTTP request. In your index view, you can check to see if your key/value pair exists and display a error message. If you refresh the page, you will notice the data from the TempData will be gone. Remember to use RedirectToAction where possible as this is more friendly with Unit Testing rather than using the HttpResponse redirect method.

I hope you have got what is ViewBag, ViewData and TempData in Asp.Net MVC and I hope you will refer this article for your need. Stay tuned and stay connected for more technical updates.