I've build a class like this:
private class TestResults
{
public bool IsAdmitted { get; set; }
public bool IsDuplicate { get; set; }
public bool IsVerified { get; set; }
}
The values of this class are set at postback by clicking a radiobutton list. Problem however is I don't know how to save this values across multiple postbacks. I thought of using viewstate but I'm not quite sure how to do it with this class.
Maybe I'm missing some important thing here.
Hope someone can point me in the right direction
thanks for your time!
Kind regards,
Mark
Just sticking this class in viewstate is pretty simple:
ViewState["SomeUniqueKey"] = myTestResults;
var testResults = (TestResults)ViewState["SomeUniqueKey"];
Your class will need to be marked with the [Serializable] attribute though.
try using the Session cache instead
var testResults = new TestResults();
//set values
Session["TestResults"] = testResults;
Retrieving them later on:
var testResults = Session["TestResults"] as TestResults;
if (testResults != null)
{
//use it
}
You can use
Session.Add("TestResults", Your_Test_Result_Object)
Session Object Explanation
If you don't need this value on other pages or in other places throughout the app, you can use viewstate.
Use the Page.ViewState object bag to store it:
public partial class Page1 : Page {
protected void button1_click(object sender, EventArgs e) {
ViewState["myObject"] = testResultsObject;
}
}
You could also wrap the access to it in a property on the page:
public partial class Page1 : Page {
public TestResults TestResults {
get{ return ViewState["TestResults"] as TestResults; }
set{ ViewState["TestResults"] = value; }
}
}
Related
I have a xamarin forms app.
There are 2 classes with data, one of the pages is filling the data.
The problem is: I'm creating new view, that should use data from both classes.
The only way i'm familiar with is to set a class as a bindingContext to pass data between pages, and it's working fine with ONE class, because apparently there couldn't be 2 bindingContext at the same time.
EXAMPLE:
1st class (all the classes are filled on the previous page. just accept that they are filled)
public class Buildings : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string _id;
public string Id
{
get { return _id; }
set
{
_id = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Id"));
}
}
}
2nd class
public class Flats : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string _num;
public string Num
{
get { return _num; }
set
{
_num = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("Num"));
}
}
}
new view:
public partial class HouseView
{
private Flats _flats;
private Buildings _buildings;
public HouseView()
{
InitializeComponent();
}
private void HouseView_OnBindingContextChanged(object sender, EventArgs e)
{
var building = BindingContext as Building;
//var flat = BindingContext as Flat;
//_flat = flat;
_building = building;
var buildingInfo = await Rest.GetHouseInfo(_building.Id, _flat.Num); //function that will return info on a current house;
// rest code
}
}
Maybe there is no need for binding context, because i'm just passing the parameters, not changing them in a view? I guess the solution can be pretty simple, and i cant figure it out....
What you are missing is understanding the concept of ViewModel, and it's relation with the views.. In this case what you need is a 3rd class (ViewModel) that handles your 2 previous class:
public class HouseViewModel : INotifyPropertyChanged
{
public Flats Flats { get; set; }
private Buildings Buildings { get; set; }
}
Also using OnBindingContextChanged is just messy and will take some performance from your app .. try to prepare your data before on your VM, so the view knows as little as possible in how to get/handle data.
There is simple way to transfer data between pages in Xamarin forms.
Add new class to the main project called Transporter.cs, and this class should be static.
Inside this class, add the variables to transfer data between other pages; then you can simply access any variable by using Transporter.Variable.
Example:
public static Transporter
{
public static string x;
}
> Now, in each page, you can simply access (set or get) the value:
Transporter.x=MyName.Text;
>In another page:
MySecondName.Text=Transporter.x;
Note: MyName is an entry field in the first page, and MySecondName is an entry field in the second page.
Also, you can define any type of variables like (Lists, int, object... etc).
I want to change my session proviced to statically typed - I just hate typing strings because of many many errors I do.
What technology am I using? ASP.NET MVC via EXT.NET MVC
I was trying to do that using web.config but the problem is that after add session state to it visual is not going to compile my code because of that session should be using strings as keys.
I want to use session by enums such as :
public enum SessionEnum{Model}
public class Bar{
void foo(){
Session[SessionEnum.Model] = "blah";
}
}
I am aware that I can create wrapper converting enums to strings but it's not very satisfying solution for me.
public class StorageWrapper{
public object this[SessionEnum enum]{ get{return Session[enum.toString()]}; //+set
}
What I did was create static object for base class for all of my controllers and then I was able to use it across them but after closing and opening the page again I wasn't able to get values from it. I guess I should serialize them somehow but I have no idea how.
Is there any way to do that?
EDIT
My session now looks like this :
[Serializable]
public abstract class DataWrapper<T> : HttpSessionStateBase
{
Dictionary<T, object> Dictionary { get; set; } = new Dictionary<T, object>();
public object this[T a]
{
get
{
try
{
return Dictionary[a];
}
catch
{
return null;
}
}
set { Dictionary[a] = value; }
}
}
[Serializable]
public class SessionWrapper : DataWrapper<SessionNames>
{}
public enum SessionNames { Model, Login, LastOpenedFile }
It's very simple.
Create a UserSession object which does everything you want (holds your values as enum etc), instantiate it, then put it in the session.
var US = new UserSession();
US.stuff = somestuff;
Session["UserSess"] = US
Then you can just always use Session["UserSess"].stuff;
Mmmm, wouldn't you use static const string instead of an enum?
using System.Web;
public static class SessionEnum
{
public static const string Model = "_Session_Model";
public static const string Login = "_Session_Login";
public static const string LastOpenedFile = "_Session_LastOpenedFile ";
}
class test
{
void test()
{
Session[SessionEnum.Model] = "blah";
}
}
ASP.NET: Is it possible to keep complex object such as List<object> is the session? If yes, how to do so? I'm trying to keep a list in the session, but I'm being told that I cannot convert that List to a string.
EDIT
[Serializable]
public class Client
{
public string ClientType { get; set; }
public string ClientName { get; set; }
public string SubClientName { get; set; }
public string Project { get; set; }
public string Service { get; set; }
public string Activity { get; set; }
}
List<Client> ListOfClients;
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
ListOfClients = new List<Client> { new Client()};
Session["ListOfClients"] = ListOfClients;//This is where the error occurs
//Cannot convert List<Client> to string...
}
}
There are many operations to execute, but the idea is to keep whatever is in the list of clients in the session.
Thanks for helping.
Yes, you can store any serializable object into a session variable. For example:
List<string> list;
Session["list"] = list;
Then to return the value:
List<string> list = (List<string>)Session["list"];
You can store anything in the session object as long as session state is in InProc mode.
Otherwise what you store has to be serialisable.
Note that the type of what you store is object, so you cast the reference that you get back:
ListOfClients = Session["ListOfClients"] as List<Client>;
Since you wrote in a comment that the error happens when compiling as opposed to at runtime, I suspect that you have some other object called Session that masks the Page.Session.
Try to hover your mouse over the Session text in Visual Studio. The tooltip should show you that Session is of type
System.Web.SessionState.HttpSessionState
If it's showing something else, you need to search both your markup (.aspx file) and code behind file to see if you have declared something else with the name/id Session and then change that name/id.
Is it possible to specify an object as a parameter in MVC with default values in some way?
E.g.
public virtual ViewResult Index(RequirementFilters requirementFilters)
I'd like to initialize the values of a couple of parameters on RequirementFilters?
At the moment I am doing
public virtual ViewResult Index(int status=1, bool required =false)
I wanted to create a Filter Object so I could re-use it but I can't figure out way of setting defaults for the object in the Action Parameters.
Thanks
Graeme
You could create a custom ActionFilter attribute and create an instance of your Filter Object there. You can provide some properties through the custom attribute.
Here's an example:
public class DefaultQuerySettingsAttribute : ActionFilterAttribute
{
public string ParameterName { get; set; }
public Type SettingsType { get; set; }
public int Rows { get; set; }
public string SortColumn { get; set; }
public string SortOrder { get; set; }
public bool PagingEnabled { get; set; }
public DefaultQuerySettingsAttribute()
{
this.ParameterName = "settings";
var defaultSettings = new QuerySettings();
this.Rows = defaultSettings.Rows;
this.SortColumn = defaultSettings.SortColumn;
this.SortOrder = defaultSettings.SortOrder;
this.PagingEnabled = defaultSettings.PagingEnabled;
}
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
base.OnActionExecuting(filterContext);
if (filterContext.ActionParameters.ContainsKey(this.ParameterName))
{
var querySettings = filterContext.ActionParameters[this.ParameterName] as QuerySettings;
if (querySettings == null || string.IsNullOrWhiteSpace(querySettings.SortColumn))
filterContext.ActionParameters[this.ParameterName] = this.GetQuerySettings();
}
}
private QuerySettings GetQuerySettings()
{
var querySettings = (QuerySettings)Activator.CreateInstance(SettingsType ?? typeof(QuerySettings));
querySettings.Rows = Rows;
querySettings.SortColumn = SortColumn;
querySettings.SortOrder = SortOrder;
querySettings.PagingEnabled = PagingEnabled;
return querySettings;
}
}
ParameterName is the name of the argument in the action method (requirementFilters in your case).
You can also specify actual type that will be instantiated by providing SettingsType.
Users sometimes prefer to see the defaults on screen, rather than allowing the system to hide the defaults internally.
A better way of having defaults will be to actually show the defaults on int UI, in the HTML by rendering it with together with the defaults. That way when someone posts the page, the defaults which you pre-rendered is also posted and binded to the model.
So try and see if you can render with defaults whatever for you are rendering and posted to the Index action.
Finally, if you can't do it that way, what is preventing you from initializing the properties with default values in the no-arg constructor while creating the object?
EDIT
Or you can use the C# language feature the null coalescent operator to implement defaults. Look here to read about it.
As long as you don't need to change the defaults per action, you can set them in the default constructor of the Model.
suppose i have one static method and i need to access viewstate from that method...how could i do so...i know it is not possible but there must be some way out.
[WebMethod]
public static string GetData(int CustomerID)
{
string outputToReturn = "";
ViewState["MyVal"]="Hello";
return outputToReturn;
}
You can get the reference to the page via HttpContext.CurrentHandler. But since Control.ViewState is protected you can't access it (without using reflection) as opposed to the Session which is accessible via HttpContext.Current.Session.
So either don't use a static method, use the Session or use this reflection approach:
public static string CustomerId
{
get { return (string)GetCurrentPageViewState()["CustomerId"]; }
set { GetCurrentPageViewState()["CustomerId"] = value; }
}
public static System.Web.UI.StateBag GetCurrentPageViewState()
{
Page page = HttpContext.Current.Handler as Page;
var viewStateProp = page?.GetType().GetProperty("ViewState",
BindingFlags.FlattenHierarchy |
BindingFlags.Instance |
BindingFlags.NonPublic);
return (System.Web.UI.StateBag) viewStateProp?.GetValue(page);
}
However, this won't work if called via WebService, because then it's outside of Page-Lifecycle.
You might be able use [WebMethod(EnableSession=true)] for your PageMethod, and use Session instead of ViewState. Remember, with a static PageMethod no instance of the Page class is ever created, so nice things like ViewState simply are not there and there is no way to make them be there.
I tried this and worked for me:
Create a class conteining the properties of the viewState you want to access to
In the constructor pass the real ViewState
Create a static instance of the class but not initialize it
In the PageLoad initialize Not static class and the static one
Access the ViewState using static class properties
public class Repository
{
public int a
{
get
{
if (_viewState["a"] == null)
{
return null;
}
return (int)_viewState["a"];
}
set
{
_viewState["a"] = value;
}
}
public StateBag _viewState;
public Repository(StateBag viewState)
{
_viewState = viewState;
}
}
static Repository staticRepo;
protected void Page_Load(object sender, EventArgs e)
{
Repository repo = new Repository(ViewState);
staticRepo = repo;
}
public static void testMethod()
{
int b = staticRepo.a;
}