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Controller to controller communication in C# MVC

I want to use the list of state controller in a district controller. Are there any better ideas.
I have tried one which is working
I put this code in the district controller by using constructor injection.
In this case, the entire code needs to be placed in the district controller.
Is there any way to reduce the code. A better way?
#region StateDropDown
public List<SelectListItem> StateDropDown()
{
List<SelectListItem> selectListItem = new List<SelectListItem>();
List<StateViewModel> stateList = Mapper.Map<List<State>, List<StateViewModel>>(_stateBusiness.GetStateForSelectList());
if (stateList != null)
foreach (StateViewModel state in stateList)
{
selectListItem.Add(new SelectListItem
{
Text = state.Description,
Value = state.Code.ToString(),
Selected = false
});
}
return selectListItem;
}
#endregion StateDropDown

This is what the term 'reusability' is invented for. Place the code in another file and make calls to it from any number of controllers you want, like code below.
//StateBusiness.cs
public class StateBusiness
{
public List<SelectListItem> GetStatesForDropdown()
{
//your logic here
return new List<SelectListItem>();
}
}
//StateController.cs
public class StateController : Controller
{
var state = new StateBusiness();
public ActionResult Index()
{
//call your code here
var states = state.GetStatesForDropdown();
//and do whatever you want
ViewBag.states = states;
return View();
}
}
//DistrictController.cs
public class DistrictController : Controller
{
var state = new StateBusiness();
public ActionResult Index()
{
//call it from here just the same
var states = state.GetStatesForDropdown();
ViewBag.states = states;
return View();
}
}

I don't know about better, but you could shorten this considerably using linq Select.
Mapper.Map<List<State>, List<StateViewModel>>(_stateBusiness.GetStateForSelectList())?
.Select(state => new SelectListItem
{
Text = state.Description,
Value = state.Code.ToString(),
Selected = false
}))?.ToList() ?? List<SelectListItem>();

If you using core one option might be to keep this off the controller and use a TagHelper this will let you inject the options into the tag with a simple attribute state-items reducing controller dependencies and keeping this state off the ViewBag while being more reusable.
Here is how it wold look in the view:
<select asp-for="State" state-items />
The TagHelper:
[HtmlTargetElement("select", Attributes = "state-items")]
public class StateItemsTagHelper : TagHelper {
private readonly StateBusiness _stateBusiness;
[HtmlAttributeName("asp-for")]
public ModelExpression For { get; set; }
public StateItemsTagHelper(StateBusiness stateBusiness) {
this._stateBusiness = stateBusiness;
}
public override void Process(TagHelperContext context, TagHelperOutput output) {
content.TagMode = TagMode.StartTagAndEndTag;
var value = For?.Model as string;
var items = _stateBusiness.GetStateForSelectList()?.Select(state => new SelectListItem {
Text = state.Description,
Value = state.Code.ToString(),
Selected = value == state.Code.ToString()
})) ?? Enumerable.Empty<SelectListItem>();
foreach(var item in items) {
output.Content.AppendHtml(item.ToHtmlContent());
}
}
}
For reusability item.ToHtmlContent is an extension method:
public static IHtmlContent ToHtmlContent(this SelectListItem item) {
var option = new TagBuilder("option");
option.Attributes.Add("value", item.Value);
if(item.Selected) {
option.Attributes.Add("selected", "selected");
}
option.InnerHtml.Append(item.Text);
return option;
}

How to get the Count or Key of TempData in another ActionResult

I am setting the value of TempData in one ActionResult of different controller and trying to get their Keys of just counts in another controller's ActionResult
public ActionResult DealProducts(FormCollection form)
{
TempData["check"] = "DealUpdated";
}
in another controller
public ActionResult CustomizedBudget()
{
var temp = TempData["doc"];
var temp = TempData["doc"].Key;//like this
if (temp.Count > 0) // or trying to get like this, but not
}

To Assign
public ActionResult DealProducts(FormCollection form)
{
TempData["check"] = "DealUpdated";
}
In CSHTML
#{
TempData.Keep("check");
}
in another controller
public ActionResult CustomizedBudget()
{
var count = TempData.Keys.Count;
var DealUpdatedValue = TempData["check"];
}

well since you have
public ActionResult DealProducts(FormCollection form)
{
TempData["check"] = "DealUpdated";
}
shouldn't you have
public ActionResult CustomizedBudget()
{
var temp = TempData["check"];
var temp = TempData["check"].Key;//like this
if (temp.Count > 0) // or trying to get like this, but not
}
?

you need to change in below Action
public ActionResult CustomizedBudget()
{ var temp = TempData["check"]; }

Static field vs TempData when passing data from ActionResult to another

Both TempData[] and static fields can be used to pass data from ActionResult to another.
Is there performance/memory difference? best practice?
I also noticed that when paging or sorting, the Detail function is recalled which lead that the list of cars should remain in memory.
public class TestController
{
private static IEnumerable<Cars> _cars;
public ActionResult Detials()
{
var uploadedCars = TempData["cars"] as IEnumerable<Cars>;
var testViewModel = new TestViewModel();
var result = TestViewModel.Process(uploadedCars);
//var result = TestViewModel.Process(_cars);
return View(result);
}
public ActionResult UploadCars(object obj)
{
// upload file ...
_cars= null; // reset value
//_cars= loader.GetAllCars(uploader);
TempData["cars"] = loader.GetAllCars(uploader);
return RedirectToAction("Detials");
}
}
}

How to pass ID to default value of another view

I have a list of incidents which can have associated jobs. I Have a separate views for incidents and jobs. From the incident index page I have the following link to create a new job for that incident:
#Html.ActionLink("Create","Create", "Job", new { id = item.IncidentID }, null)
which takes the incident ID from that field and loads the Job view. I want to pass the ID as a default value for creating a new job, so the job will be assigned the incident ID.
I made this controller:
public ActionResult Create(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
var newid = id;
ViewBag.ActionCode = new SelectList(db.ActionTypes, "ActionCode", "ActionType1");
ViewBag.IncidentID = new SelectList(db.Incidents, "IncidentID", "DefectFreeText");
return View();
}
How can I assign a default value to the form on the create job view ? I thought something like this:
#Html.EditorFor(model => model.IncidentID, id/newid)
Can anyone help me figure out what I am doing wrong?

I am assuming you want to set a default item for your Incidents dropdown list when user pass that to your create action method as a querystring. I would avoid using ViewBag approach to transfer your dropdown list data to the view and switch to a strongly typed viewmodel approach.
First create a viewmodel for our create view.
public class CreateJobVM
{
public int IncidentID { set;get;}
public int ActionTypeID { set;get;}
public List<SelectListItem> ActionTypes { set;get;}
public List<SelectListItem> Incidents{ set;get;}
public CreateJobVM()
{
ActionTypes =new List<SelectListItem>();
Incidents=new List<SelectListItem>();
}
}
And in your GET view,
public ActionResult Create(int? id)
{
var vm=new CreateJobVM();
vm.ActionTypes=GetActionTypes();
vm.Incidents=GetIncidents();
if(id.HasValue)
{
//set the selected item here
vm.IncidentID =id.Value;
}
return View(vm);
}
Assuming GetActionTypes and GetIncidents method returns a list of SelectListItems, From a DB table/ XML /whatever place you have data
public List<SelectListItem> GetActionTypes()
{
List<SelectListItem> actionTypesList = new List<SelectListItem>();
actionTypesList = db.ActionTypes
.Select(s => new SelectListItem { Value = s.ID.ToString(),
Text = s.Name }).ToList();
return actionTypesList;
}
and in your view which is strongly typed to CreateJobVM
#model CreateJobVM
#using(Html.Beginform())
{
#Html.DropDownListFor(s=>s.ActionTypeID ,Model.ActionTypes)
#Html.DropDownListFor(s=>s.IncidentID,Model.Incidents)
<input type="submit" />
}
When you post the form you can check the property values to get the values user selected in the form
[HttpPost]
public ActionResult Create(CreateJobVM model)
{
//check for model.IncidentID, ActionTypeID
// to do : Save and redirect
}

Just pass it with the help of ViewBag/ViewData
ViewBag.DefaultId=id;
return View();
If you have a model based view
YourViewModel.DefaultId=id;
return View(YourViewModel);
In View,
#ViewBag.DefaultId
or with ViewModel
YourViewModel.DefaultId

Reuse model data in a post action

In my viewmodel, I have a list of items I fetch from the database and then send to the view. I would like to know if it's possible to avoid having to refill the options property whenever I hit a Post action and need to return the model (for validation errors and what not)?
In webforms, this wouldn't be necessary.
Edit: I was not clear. My problem is with the SelectList options I use for my DropDownLists. Everything gets posted, but if I have to return to the view (model is invalid), I have to reload the options from the database! I want to know if this can be avoided.
My viewmodel:
public class TestModel
{
public TestModel()
{
Departments = new List<SelectListItem>();
}
public string Name { get; set; }
public int Department { get; set; }
public IEnumerable<SelectListItem> Departments { get; set; }
}
My view:
#model MvcApplication1.Models.TestModel
#using (Html.BeginForm())
{
#Html.TextBoxFor(m => m.Name)
#Html.DropDownListFor(m => m.Department, Model.Departments)
<input type=submit value=Submit />
}
My controller (do notice the comment on HttpPost):
public ActionResult Index()
{
TestModel model = new TestModel
{
Name = "Rafael",
Department = 1,
Departments = new List<SelectListItem>
{
new SelectListItem { Text = "Sales", Value = "1" },
new SelectListItem { Text = "Marketing", Value = "2", Selected = true },
new SelectListItem { Text = "Development", Value = "3" }
}
};
// Departments gets filled from a database.
return View(model);
}
[HttpPost]
public ActionResult Index(TestModel model)
{
if (!ModelState.IsValid)
{
//Do I have to fill model.Departments again!?!?!?
return View(model);
}
else { ... }
}
Thanks in advance.
Edit: FYI, my solution was to use the Session variable.

Just need to strongly type your view, and change your controller method to have a parameter of that class type.
That is, the view
#model MyNamesspace.Models.MyModel
...
#using (Html.BeginForm())
{
....
}
And you controller method which is posted to.
[HttpPost]
public ActionResult MyAction(MyModel model)
{
...
}
EDIT: Also make sure you have form fields for each property of the model which you need posted to the controller. My example is using Razor too BTW.

I encountered a similar problem when trying to create an Order wizard in MVC (one where each page of the wizard is implemented as a partial view loaded by AJAX). I highly doubt it is the suggested method but my way of solving this was to call a custom MergeChanges method in each action called by my wizard:
public Order MergeChanges(Order newOrder)
{
var sessionHistory = (List<string>)Session["sessionHistory"];
if (sessionHistory == null || sessionHistory.Count == 0)
return MergeChanges(newOrder, -1);
return MergeChanges(newOrder, MasterViewController.GetStepNumberByName(sessionHistory.Last()));
}
public Order MergeChanges(Order newOrder, int step)
{
PreMerge(newOrder);
Order result = null;
try
{
ApplyLookups(ref newOrder);
Order oldOrder = (Order)Session["order"];
if (oldOrder == null)
{
Session["order"] = newOrder;
result = newOrder;
}
else
{
List<TypeHelper.DecoratedProperty<ModelPageAttribute>> props = null;
newOrder.GetType().GetDecoratedProperty<ModelPageAttribute>(ref props);
props = props.Where(p => (p.Attributes.Count() > 0 && p.Attributes.First().PageNumber.Contains(step))).ToList();
foreach (var propPair in props)
{
object oldObj = oldOrder;
object newObj = newOrder;
if (!string.IsNullOrEmpty(propPair.PropertyPath))
{
bool badProp = false;
foreach (string propStr in propPair.PropertyPath.Split('\\'))
{
var prop = oldObj.GetType().GetProperty(propStr);
if (prop == null)
{
badProp = true;
break;
}
oldObj = prop.GetValue(oldObj, BindingFlags.GetProperty, null, null, null);
newObj = prop.GetValue(newObj, BindingFlags.GetProperty, null, null, null);
}
if (badProp)
continue;
}
if (newObj == null)
continue;
var srcVal = propPair.Property.GetValue(newObj, BindingFlags.GetProperty, null, null, null);
var dstVal = propPair.Property.GetValue(oldObj, BindingFlags.GetProperty, null, null, null);
var mergeHelperAttr = propPair.Property.GetAttribute<MergeHelperAttribute>();
if (mergeHelperAttr == null)
{
if (newObj != null)
propPair.Property.SetValue(oldObj, srcVal, BindingFlags.SetProperty, null, null, null);
}
else
{
var mergeHelper = (IMergeHelper)Activator.CreateInstance(mergeHelperAttr.HelperType);
if (mergeHelper == null)
continue;
mergeHelper.Merge(context, HttpContext.Request, newObj, propPair.Property, srcVal, oldObj, propPair.Property, dstVal);
}
}
result = oldOrder;
}
}
finally
{
PostMerge(result);
}
return result;
}
Since my case was doing this with a wizard, only specific values applied to each page so in order to only account for properties known to the current page of the wizard, I've implemented some attributes, a (admittedly over complex) ViewController layer, and a custom validation layer. I can share some more code but the code above does the grunt work if you aren't in such a complex situation. If there is a better way, I hope to learn it from the answers to this question because this was a PITA.

I am surprised this question doesn't come up more often, and I am also surprised the obvious (IMHO) answer isn't standard practice these days: nearly all POSTs should be Ajax-based. This solves a whole slew of problems including
No need to repopulate form data when you have e.g. a validation error, or application error (exception). This is particularly desirable when you have client-side state (in true rich web application fashion).
No compulsion to perform client-side validation. Validation can be 100% server-side (where it must be anyways) and the user experience is nearly the same.
Of course, there is some initial work you need to do to build out a framework for this, for example, I have a set of AjaxUpdate, AjaxNothing, AjaxRedirect, AjaxErrors ... ActionResult types which render Json which is processed by some custom Javascript. But once you get that in place, it's smooth sailing.