Develop Reference

How to keep dropdown list from one view to another

in my controller, I have Create actions for Get and Post.
On Get action, I load dropdown data list and show it in view, while I keep only value of selected item. Then I click on submit and call Post action of Create and logic is finished.
But when I call Create action, and model isn't valid, I go back to Get. And here starts the problem, because my dropdown data no longer exists. So I can on my Create action, when model is not valid, again load dropdown data from database, but my idea is to keep and move dropdown data list from Get to Post action, like I sometimes did with "hidden input id". But i have no idea what html tag or helper use for data List.
Something like:
<Select type="hidden" value="#Model.DataList">

I think that transfert the DropDownlist elements between get and post actions is not the right approach. It could make the server calls too long, especially if you have several elements.
I suggest you to create a cache (session cache for example) of your DropDownList items and use it during the get action.
With this system, when you have an invalid model, the get will reload the data without calling the database.

Refresh page with new data after Update in MVC5

I have a MVC5 page that is shows Customer's information in Text box then you can update some of the data and push Update button. it is going to update info but it is not showing the new value after pushing the update button, you have to leave a page and comeback to see a new value.

UpdateCustomer and (presumably) UpdatePassword should not return a View but instead should return a RedirectResponse back to the [HttpGet] version of the Edit action. This is known as a Post-Redirect-Get pattern and is the preferred way of redisplaying the same page the user just edited. By returning the view with the same model that was posted you're just showing the user what they originally typed in. You're also leaving yourself open to multi-postback situations if the user tries refreshing their browser.
You also seem to be fighting the framework. If you've got two buttons on the page that perform two different actions you should have two forms that each POST to a different controller action.

How to return an object from controller to View which may not be model

I am very new to MVC and I am not too conversant with the best practices here. I am facing a design issue which may be common or uncommon to newbies like me. My problem is the following:
I have a page with two parts in it.
Grid Control (with Employee basic info in it)
Employee Details (When someone clicks on Grid row, it loads all the details about the employee)
I am using KendoGrid and it is getting all its data from an ActionMethod from my controller.
Now, when I click on the row, I have the following options:
I call some ActionMethod in Controller and return all the Details
Should I use partial View with a separate model so that ActionMethod in response calls RenderPartialView()?
Should I NOT create a partial View, have Actionmethod return JSON and parse it in the Model?
3.1 If I go for this option then would the JSON be part of model?
3.2 If it is not going to be part of model, how can I use JSON to render the View?
Or probably I am missing something basic here?

Yes you can use action method returning JsonResult. what needs to be done is keep the uielements you need to show on the click of grid row in the page itself. initiate a ajax call to the action method and on success update the values of the UI elements from the values received in JSON and make the entire DIV as visible which holds the total information.
Instead of passing entire HTML over the network I think you can opt for json.
An example you can find at following location
example

Controller calling itself and passing a value

How to pass data from the controller to itself?
Consider this example:
I have a page that consists of two parts: (1) a simple html form with a couple of text boxes and a submit button and (2) a table that is updated when the button from part (1) is pressed. When it happens, the data from the form has to be appended to the end of the table.
As I see it, there should exist a List of objects. Every time the button is pressed, the controller is called with two parameters: the old list of objects and textbox values. Then, the controller generates the object, adds it to the list and passes the new list to the view. The view is rendered with the new data and rows are successfully added to the table.
However, that requires reloading of the page and that feels kinda wrong.
The problem is, that there is no static object that can contain the list permanently, or at least that exists during these controller-self-calls. If there was such, I would not have to pass the whole list (which, as I said, I can't even do) but just new textbox values.
I have heard that partial views can solve the problem, but I can't see how.
What can I do?

For starters, as you said you'd like to achieve this without javascript, I see no way of avoiding: reloading of the page and that feels kinda wrong.
Not sure as well how partial views will make things work since they're rendered from your main view and require the same or part of your model, so you'll need to have that data there.
You have to get the information back from the controller, and the controller must get this information somehow so as I see it, these are your options:
Keep part (2) inside your form, thus making both parts available when you hit the controller. Model will get populated with the values you need and then the data is available for you when you're back at the View.
Keep a hidden input field inside part (1) containing the data you require to create the list. It's similar in concept to option #1 but I don't like this method too much, you'll have to do some parsing on that input field and this is not very elegant.
You could also try use Session or database but I think the latter is an overkill and a hit on performance so I wouldn't go with that.

If you don't have a database backing the form data, you could use Session data to hold the List.
In the controller, do something like this:
[HttpPost]
public ActionResult AddToList(object newObject)
{
var list = Sesssion["List"] as List<Object>;
if (list == null) {
list = new List<Object>();
Session["List"] = list;
}
list.add(newObject);
return View(list); // Assuming the view is a strong-typed view with List<Object> as model
}
As for partial views, they do not alone solve the problem of reloading the page. The solve the problem of a reusable, self-containing component of the page. If you don't like the reload of the page, you can use partial views together with Ajax calls though, in order to refetch the table whenever a new item is added. Here is an example

Redisplaying old data on a view mvc

I have an MVC application in which I create a search page to find projects I've created. Once the user enters the search criteria, the data is passed back to the controller as a model object and I take this data to search for any projects that match. The search page is redisplayed with the original criteria the user entered plus any projects that were found.
The user can now go an click on a row (the results of their search) and edit that data on another page. When the user hits the save button (on the other page), I save the data and go back to the search page. I don't have the original data (the search model object) to redisplay. How do I get it back? I'm thinking that I should just thorugh my model object that I got when the method was called through the controller into my session object and then retrieve it when I come back to the search page. Is there a more elegant solution to getting the data from the model object back when I return to the search page?

You can use TempData["whatevever"]= yourObject and the data there will exist until it is read the next time and then it is removed. Its like the session object, but is removed after you read it.