Hi I have a problem that drives me crazy. I have a dropdown list in one page of my project, which should act like on all the other dropdowns on all the other pages but it doesn't and I'm wondeing why.
Here you will see the code in the cshtml page. It's a normal dropdown:
<p>
Specify a organisation to search in
#Html.DropDownList("OrganisationList", new SelectList(ViewBag.OrganisationList, "ID", "Name", ViewBag.SelectedOrganisation))
</p>
In the controller I have a method to bind the dropdownlist and a method that calls the view:
private void BindAllOrganisations()
{
List<OrganisationModel> OrganisationList = new List<OrganisationModel> { new OrganisationModel { ID = null, Name = "Select" } };
foreach (var Organisation in DatabaseConnection.DataContextRead.GetTable<Organisation>())
{
OrganisationList.Add(new OrganisationModel { ID = Organisation.OrganisationId, Name = Organisation.Name });
}
ViewBag.OrganisationList = OrganisationList;
}
/**
* Loads the ManageUserView with all users from a specific organisation unit
**/
[AzaraAuthorization(RequiredRoles = new[] { RolesEnum.Admin })]
public ActionResult ManageUsersFromOrgUnit(int Id)
{
try
{
var orgUnit = organisationUnitManagement.GetSingleUnit(Id);
List<AzaraUser> AzaraUserList = azaraUserManagement.GetAllUserFromOrganisationUnit(orgUnit);
ViewBag.FromOrgUnits = Id;
BindAllOrganisations();
ViewBag.SelectedOrganisation = orgUnit.Organisation.OrganisationId;
return View("ManageUsers", AzaraUserList);
}
catch (BusinessObjectNotRetrievableByIdException exc)
{
ExceptionHandling.BusinessObjectNotRetrievableByIdExceptionOccured(exc, "ManageUsersFromOrgUnit(int Id)", "ManageUsersController");
return RedirectToAction("Index", "Home", new { Info = "A program error occured. The administrator get informed. Apologize the inconvenience." });
}
}
I can't find the problem. Also if I replace ViewBag.SelectedOrganisation on the Page with 1 (I know there is a model with value 1 in the database behind) it selects the value with null. Here is the used model for the list:
public class OrganisationModel
{
public int? ID { get; set; }
public string Name { get; set; }
}
Could there be a bug or what have I missed?
Related
Ok, I'm trying to do a proper dropdown in Core 3.1. In this example https://learn.microsoft.com/en-us/aspnet/core/mvc/views/working-with-forms?view=aspnetcore-3.1#the-select-tag-helper
Model has a new list with hardcoded values
public string Country { get; set; }
public List<SelectListItem> Countries { get; } = new List<SelectListItem>
{
new SelectListItem { Value = "MX", Text = "Mexico" },
new SelectListItem { Value = "CA", Text = "Canada" },
new SelectListItem { Value = "US", Text = "USA" },
};
I looked for examples where the list is coming from the database but they are very inconsistent. The only way I was able to do the dropdown list is with the ViewBag which is not advised.
I have two models. 1.
public partial class Glossary
{
public int UniqueId { get; set; }
public int Category { get; set; }
public string DisplayText { get; set; }
}
which is my view model
public partial class AdminUser
{
[Key]
public int Id { get; set; }
public string UserName { get; set; }
public string UserLocation { get; set; }
public string UserStatus { get; set; }
//public IEnumerable<Glossary> Glossary { get; set; } //I used this for ViewBag
public List<SelectListItem> UserLocations { get; } = new List<SelectListItem>
{
according to the example my query should go here
};
}
Here is my controller:
public IActionResult Create()
{
// This is the ViewBag that worked with HTML helpers, but I'm trying to use tag-helpers.
/*IEnumerable<SelectListItem> LocationsList = _context.Glossary.Where(x => x.Category == 1).Select(x => new SelectListItem
{
Value = x.UniqueId.ToString(),
Text = x.DisplayText
});
ViewBag.LocationsList = LocationsList;
*/
return View();
}
All examples that found were hardcoded lists and nothing with getting it from the database. What is the proper way to get the data from the Glossary table through the view model with ViewBag? Any pointers are appreciated.
ALSO:
When using this example: Select Tag Helper in ASP.NET Core MVC
When I used
public SelectList Employees { set; get; }
I got error: InvalidOperationException: The entity type 'SelectListGroup' requires a primary key to be defined. If you intended to use a keyless entity type call 'HasNoKey()'.
Both of my tables have PK and adding [Key] to Glossary model didn't fix it.
If you'd like to retrieve data from db and populate a dropdown with retrieved data through a view model (or ViewBag), you can refer to following code snippet.
In AdminUser view model class, include these properties
public string Selected_Glossary { get; set; }
public List<SelectListItem> Glossary_List { get; set; }
In controller
public IActionResult Create(AdminUser model)
{
var adminuser_model = new AdminUser
{
UserName="test"
//for other properties
};
//retrieve data from Glossary table
var items = _context.Glossary.Where(x => x.Category == 1).Select(x => new SelectListItem
{
Value = x.UniqueId.ToString(),
Text = x.DisplayText
}).ToList();
//pass dropdown items through a view model
adminuser_model.Glossary_List = items;
////pass dropdown items through ViewBag
//ViewBag.Glossary_List = items;
return View(adminuser_model);
}
In view page
#model AdminUser
#{
ViewData["Title"] = "Create";
}
<h1>Create</h1>
<form asp-controller="Home" asp-action="Create" method="post">
<select asp-for="Selected_Glossary" asp-items="Model.Glossary_List"></select>
#*populate it through ViewBag*#
#*<select asp-for="Selected_Glossary" asp-items="ViewBag.Glossary_List"></select>*#
<input type="submit" value="Submit" />
</form>
Test Result
I am trying to create my first ASP.NET MVC application but since two days I cannot solve my problem.
I am using Entity Framework Code First approach. I want to create DropDownListFor but there is always this error:
System.NullReferenceException
System.Web.Mvc.WebViewPage.Model.get returned null.
My Model:
public class Animals
{
public int AnimalsId { get; set; }
public int ClientsId { get; set; }
public string Name { get; set; }
public int TypesId { get; set; }
public float Age { get; set; }
public float Weight { get; set; }
public virtual Types Types { get; set; }
public IEnumerable<Clients> ClientsList { get; set; }
public virtual ICollection<BookVisit> AnimalsVisits { get; set; }
}
My controller:
public ActionResult Create([Bind(Include = "AnimalsId, ClientsId, Name, TypesId, Age, Weight")] Animals animals)
{
var person = new List<Clients>
{
new Clients { ClientsId = 50, Name = "Timo", Surname = "Werner", Email = "timo.werner#gmail.com", Phone = 123123123 }
};
var animalsView = new Animals
{
ClientsList = person.Select(x => new Clients
{
ClientsId = x.ClientsId
})
};
if (ModelState.IsValid)
{
db.Animals.Add(animals);
db.SaveChanges();
return RedirectToAction("List", "Animal");
}
return View(animalsView);
}
My view (only #model and dropdown):
#model xyz.Models.Animals
#Html.DropDownListFor(model => model.ClientsId, new SelectList(Model.ClientsList, "ClientsId", "Name", "Surname", "Email", "Phone"))
Could you please take a look ?
From the comments, it looks like you are not passing a valid view model object to the view. Your view code is expecting a valid model passed to it and the helper methods are using different properties of that.
public ActionResult Create()
{
var clients = new List<Clients>
{
new Clients { ClientsId = 50, Name = "Timo" },
new Clients { ClientsId = 51, Name = "Microsoft" }
};
var vm = new Animals
{
ClientsList = clients
};
return View(vm);
}
Also your current code which calls the DropDownListFor is wrong. When you create a SelectList from a collection, you have to pass the dataValue field and dataText fields.
#model Animals
#Html.DropDownListFor(model => model.ClientsId,
new SelectList(Model.ClientsList, "ClientsId", "Name"))
This error may also be caused by trying to use a null model in razor view. In such case check if the model is null or not before using it as shown below:
#if (Model != null) {
<a onclick="get('#Url.Action("GetEmployee", "DemoController")', #Model.Id)" ></a>
}
What I have is a form with multiple inputs that I want to use to query database for some results. Form has some default values and it all works, however I have problem submitting it to itself.
The returned error is "No paramaterless constructor defined for this object" and it is caused by SelectList object.
I have tried this solution and made psUserType private with getter and setter and intialized it as empty list, but then my dropDown menu had no values on start. Not sure why GetUserTypes hadn't filled them.
What am I doing wrong here? How does one have both preselected values and also send the same model with user-selected values, while also displaying results on the same page?
Does it make sense to use the same model for all 3 actions: 1. display form and inputs with default values 2. post selected values during submit 3. return results and selected values? I've read this solution also but not sure how to use 2 or 3 separate models here.
Any help is appreciated. Thanks in advance.
Model
public class SearchDownloadsModel
{
public SelectList psUserType { get; private set; } //causes problem on submit
public string psText { get; set; }
public MultiSelectList psColumns { get; private set; }
public IEnumerable<ResultsRowModel> psResults { get; set; }
public SearchDownloadsModel()
{
this.psUserType = GetUserTypes();
this.psColumns = GetColumns();
this.psResults = new List<ResultsRowModel>(); //empty by default
}
public SelectList GetUserTypes()
{
List<SelectListItem> items = new List<SelectListItem>()
{
new SelectListItem { Value="user", Text="Single User" },
new SelectListItem { Value="group", Text="User group" },
...
};
return new SelectList(items, "Value", "Text");
}
public MultiSelectList GetColumns()
{
List<SelectListItem> items = new List<SelectListItem>()
{
new SelectListItem { Value = "user", Text="Username" },
new SelectListItem { Value = "file", Text="Filename" },
new SelectListItem { Value = "titl", Text="Title" },
new SelectListItem { Value = "auth", Text="Author" },
...
};
return new MultiSelectList(items, "Value", "Text");
}
}
public class ResultsRowModel
{
public int ID { get; set; }
public string EventTime { get; set; }
public string FileName { get; set; }
public string FilePath { get; set; }
public string UserName { get; set; }
...
}
View
#model Proj.Models.SearchDownloadsModel
#using (Html.BeginForm("Downloads", "Home", FormMethod.Post))
{
#Html.DropDownListFor(x => x.psUserType, Model.psUserType)
#Html.TextBoxFor(x => x.psText)
#Html.ListBoxFor(x => x.psColumnsSelected, Model.psColumns, new { multiple = "multiple" })
<button type="submit" class="btn btn-primary">Search</button>
}
#if (Model.psResults != null && Model.psResults.Any())
{
<table>
<tr>
<th>User</th>
<th>File</th>
</tr>
#foreach (var row in Model.psResults)
{
<tr>
<td>#row.UserName</td>
<td>#row.FileName</td>
</tr>
}
</table>
}
Controller
[HttpGet]
public ActionResult Downloads()
{
SearchDownloadsModel model = new SearchDownloadsModel();
model.psColumnsSelected = new List<string>() { "user", "file" }; //preselected values
return View(model);
}
[HttpPost]
public ActionResult Downloads(SearchDownloadsModel model)
{
model.psResults = queryDatabase(model);
return View(model);
}
private List<ResultsRowModel> queryDatabase(SearchDownloadsModel model)
{
//...
}
EDIT: Added ResultsRowModel under SearchDownloadsModel
In ASP.NET MVC you should only put variables containing the posted or selected values in the ViewModel class. Select List items are considered extra info and are typically passed from the Action Method into the View (.cshtml) using ViewBag items.
Many of the rendering extension methods are even written specifically for such an approach, leading to code such as this:
Controller
ViewBag.PersonID = persons.ToSelectList(); // generate SelectList here
View
#Html.DropDownListFor(model => model.PersonID)
#* The above will look for ViewBag.PersonID, based on the name of the model item *#
The DropDownListFor generates a <select> element with the name of the property you bind it to. When you submit the form, that name will be included as one of the form fields and its value will be the option's value you select.
You're binding the DropDownList to a property of type SelectList (psUserType) and when your action is called, a new instance of SelectList must be created in order to bind the form field to it. First of all, the SelectList class does not have a parameterless constructor and, thus, your error. Secondly, even if a SelectList could be created as part of model binding, the <select> element is submitting a string value which wouldn't be convertible to SelectList anyways.
What you need to do is to add a string property to your SearchDownloadsModel, for example:
public string SelectedUserType { get; set; }
Then bind the dropdownlist to this property:
#Html.DropDownListFor(x => x.SelectedUserType, Model.psUserType)
When you submit the form, this new property will have the value you selected in the drop down.
Peter's answer and Stephen's comments helped me solve the problem.
Pehaps someone will find it useful.
Any further suggestions always welcome.
Model
public class PobraniaSzukajModel
{
public IEnumerable<SelectListItem> UserTypes { get; set; }
public string psSelectedUserType { get; set; }
public IEnumerable<SelectListItem> Columns { get; set; }
public IEnumerable<string> psSelectedColumns { get; set; }
public string psText { get; set; }
public ResultsModel psResults { get; set; }
}
View
#Html.ListBoxFor(x => x.psSelectedUserType, Model.Columns)
#Html.TextBoxFor(x => x.psText)
#Html.ListBoxFor(x => x.psSelectedColumns, Model.Columns)
Controller
[HttpGet]
public ActionResult Downloads()
{
SearchDownloadsModelmodel = new SearchDownloadsModel();
model.UserTypes = GetUserTypes();
model.Columns = GetColumns();
model.psColumnsSelected = new List<string>() { "user", "file" }; //preselected values
return View(model);
}
[HttpPost]
public ActionResult Downloads(SearchDownloadsModel model)
{
model.UserTypes = GetUserTypes();
model.Columns = GetColumns();
model.psResults = GetResults(model);
return View(model);
}
public SelectList GetUserTypes()
{
//...
}
public MultiSelectList GetColumns()
{
//...
}
public ResultsModel GetResults()
{
//...
}
I am trying to populate a web grid view with static data but I am not having any luck.
I always get the error:
"A data source must be bound before this operation can be performed".
I understand where the error is coming from by setting up breakpoints. Basically, when the page is loaded up, the code never accesses the Account() function. Since it doesn't do that, allFiles is never initialized and returned.
Would the best way to do this be to call Action() from the View and initialize all files? I've read other questions regarding the same error but no one highlighted the fact that the code is not accessing the controller function.
Here is the Controller:
public ActionResult Account()
{
FileModel file = new FileModel();
List<FileModel> allFiles = new List<FileModel>();
file.FileID = "1";
file.UserID = "1";
var data = allFiles;
return View(data);
}
Here is the Model
public class FileModel
{
public string FileID { get; set; }
public string UserID { get; set; }
public string FileName { get; set; }
public string AddedOn { get; set; }
public int Downloads { get; set; }
public int Show { get; set; }
}
Here is the View
#model IEnumerable<GridTest1.Models.FileModel>
#{
ViewBag.Title = "Files";
WebGrid grid = new WebGrid(Model);
}
<h2>People</h2>
#grid.GetHtml(columns: new [] {
grid.Column("FileID"),
grid.Column("UserID")
})
your controller coding order is wrong. Check the following code
public ActionResult Account()
{
// Assign a value to class
FileModel file = new FileModel();
file.FileID = "1";
file.UserID = "1";
file.FileName = "Text.txt";
file.AddedOn = "AddedOn";
// Create instance for all file
List<FileModel> allFiles = new List<FileModel>();
// Add file model to list
allFiles.Add(file);
// Pass the file list to view
return View(allFiles);
}
View
#model List<GridTest1.Models.FileModel>
#{
ViewBag.Title = "Files";
WebGrid grid = new WebGrid(Model);
}
#grid.GetHtml(columns: new[] {
grid.Column("FileID"),
grid.Column("UserID"),
grid.Column("FileName"),
grid.Column("AddedOn"),
})
This will work
I have a list of checkboxes generated in the View using the following code:
using (Html.BeginForm("UpdateItems", "Home", FormMethod.Post)) {
foreach (myProject.Models.item t in ViewBag.Items)
{
<div>
#Html.CheckBox("chkT", t.selected, new { id = "chkT" + t.id })
#Html.Label(t.description)
</div>
}
<button type="submit" class="mfButton" value="SaveItemss">Save Changes</button>
}
What I need to is to be able to get the values of these generated checkboxes in the controller. So far I have the following:
public ActionResult UpdateItemss(List<bool> chkT)
{
return View();
}
However this being a boolean only give me true or false and the id of the values to which they belong. Is there a way get the name/value pair?
Thanks
Rather than using ViewBag, I would use strongly typed view. I would create a model and add the lists as property. My Models should look like:
public class Test
{
public int Id { get; set; }
public List<Item> Items { get; set; }
}
public class Item
{
public int Id { get; set; }
public bool Selected { get; set; }
public string Description { get; set; }
}
In the controller I am passing the model with dummy data:
public ActionResult Index()
{
Test model = new Test()
{
Id = 1,
Items = new List<Item>()
{
new Item {Id = 1, Selected = false, Description = "Item1"},
new Item {Id = 2, Selected = false, Description = "Item2"},
new Item {Id = 3, Selected = false, Description = "Item3"}
}
};
return View(model);
}
In my View I am using for loop to generate list of Items:
#model MVCTest.Models.Test
#using (Html.BeginForm("UpdateItems", "Home", FormMethod.Post)) {
#Html.HiddenFor(m=>m.Id)
for (int i = 0; i < Model.Items.Count; i++)
{
<div>
#Html.HiddenFor(m=>m.Items[i].Id)
#Html.CheckBoxFor(m=>m.Items[i].Selected, new {id = "checkbox_" + i} )
#Html.DisplayFor(m=>m.Items[i].Description)
</div>
}
<button type="submit" class="mfButton" value="SaveItemss">Save Changes</button>
}
In the controller I am catching the posted model and find all Items inside its Items property:
[HttpPost]
public ActionResult UpdateItems(Test model)
{
if (model != null)
{
// You can access model.Items here
//Do whatever you need
}
return View(model);
}
I would suggest to read this blog: ASP.NET Wire Format for Model Binding to Arrays, Lists, Collections, Dictionaries.