I have a MVC 3 applicaiton in which I pass a vewmodel from the controller to the view. The vewmodel contains a couple of List<> properties.
public ActionResult MainView()
{
var model = GetViewModel();
return View("SignificantEventsView", model);
}
private SignificantEventsViewModel GetViewModel()
{
var viewModel = new SignificantEventsViewModel();
List<County_Codes> countyCodes = GetCountyCodeList();
List<String> stateNames = countyCodes.OrderBy(o=>o.County_st).Select(o => o.County_st ).Distinct().ToList();
viewModel.selectedState = stateNames.FirstOrDefault();
viewModel.CountyCodesList = countyCodes;
viewModel.StateNames = stateNames;
viewModel.SelectedCounties = new String[]{};
viewModel.SelectedCountyCodes = new String[] { };
viewModel.UnSelectedCounties = new String[] { };
viewModel.UnSelectedCountyCodes = new String[]{};
return viewModel;
}
The View looks like this:
#model ServicingPortal.ViewModels.SignificantEventsViewModel
#{
ViewBag.Title = "Significant Events";
}
<h2>SignificantEvents</h2>
#using (Html.BeginForm("RefreshCounties", "SignificantEvents", FormMethod.Post, new { id = "significantEventsForm", Model }))
{
<fieldset>
<span class="SpanTextboxEdit">
#Html.Label("states", "States")
<br />
<br />
#Html.DropDownListFor(o => #Model.selectedState
, new SelectList(Model.StateNames)
, new { id = "stateDropDown", onchange = "submit()", name = "test" })
</span>
</fieldset>
...
}
When the StateDropdownList is changed the veiwmodel is passed back to the controller, but the countyCodes list is always null.
I tried adding #Html.HiddenFor(o => #Model.CountyCodesList) in the view, but it still returns null. The only values that don't seem to be null are the primitive types such as String or String[]. Even the List stateNames is null.
I don't want to rebuild the county code list on each post back because there is substantial overhead involved. I have to create the list from all active loans in the database, of which there are thousands.
How can I get a List<> to persist from the view to the controller?
I should explain what I'm trying to acheive here.
I have a dropdown and a multiselect list box. The dropdown contains states and the listbox contains counties filtered by the selected state.
I need to filter the listbox contents when the selected state changes.
It would make sense to perform this task on the client side, but I have not found a good solution.
I will admit my javascript skills are quite limited.
All the solutions I researched one way or another involved filtering the county list on the server side.
I can accomplish this on the server side easy enough, but I thought that since I have already built the list, why not keep it intact instead of going to the backend each time.
The short answer is that you can't really do what you're trying to do. You're kind of trying to solve the wrong problem. You should look at using caching on the server side to prevent going back to the database to construct the county list every time.
I solved this by using TempData. On the postback action I can get the County List from temp data and set the ViewModel CountyCodeList to this value.
Related
I am using JQGrid with the Trirand.Web.Mvc class, and trying to figure out how to do custom paging.
I have seen the paging demos here
The problem with these demos is that they bind directly to a linq context object and lets MVC take care of the paging.
// This method is called when the grid requests data. You can choose any method to call
// by setting the JQGrid.DataUrl property
public JsonResult PerformanceLinq_DataRequested()
{
// Get both the grid Model and the data Model
// The data model in our case is an autogenerated linq2sql database based on Northwind.
var gridModel = new OrdersJqGridModel();
var northWindModel = new NorthwindDataContext();
// return the result of the DataBind method, passing the datasource as a parameter
// jqGrid for ASP.NET MVC automatically takes care of paging, sorting, filtering/searching, etc
return gridModel.OrdersGrid.DataBind(northWindModel.OrdersLarges);
}
The data set I want to bind to is quite complex and I am returning it from a stored procedure, which does the paging for me.
So all I have to give JQGrid is the correct size of rows for a specific page of the entire resultset. I can also return the total row count.
So I have my results in a List myListOfObjects.
I can pass this into the DataBind using myListOfObjects.AsQueryable()
The problem is, JQGrid thinks there is only {page size} rows, so does not display any of the paging options.
Is it possible to pass in the total row count?
Other grids, like Teleriks MVC grid allows you to pass in the Total row count, and it displays the paging correctly
Ok, so I've managed to solve this myself. There may be other ways to do it, if so I'd love to hear them!
The JQGrid.DataBind produces an JsonResult object, whose Data value is set to Trirands own object Trirand.Web.Mvc.JsonResponse
It's an internal class to their Trirand.Web.Mvc, so i had to copy its structure which I could see using Visual Studio debugging.
It has:
page - the current page number
records - the total record count
rows - of type Trirand.Web.Mvc.JsonRow (which I need to replicate too)
total - the total number of pages needed
JsonRow looks like:
cell - a string array of your columns
id - your row ID
So my code looked like this:
var jsonList = new List<JSONRow>();
myData.ForEach(x => jsonList.Add(new JSONRow(x)));
var jsonResult = Json (new
{
page = page,
rows = jsonList.ToArray(),
records = totalRows,
total = Math.Round((double)totalRows / rows, MidpointRounding.AwayFromZero)
}, JsonRequestBehavior.AllowGet);
return jsonResult;
My JsonRow looks like this:
public class JSONRow
{
public string[] cell { get; set; }
public string id { get; set; }
public JSONRow(MyObjectType myObject)
{
id = myObject.id;
cell = new string[3];
cell[0] = myObject.Col1;
cell[1] = myObject.Col2?? "";
cell[2] = myObject.Col3?? "";
}
}
I'm trying to use the WebGrid html helper in ASP.NET MVC 3 to autogenerate the columns according to the information found in the ModelMetadata. For example the code in a view that accepts a list of objects would be:
var grid = new WebGrid(Model);
#grid.GetHtml(columns: ViewData.ModelMetadata.Properties.Single.Properties
.Select(p => grid.Column(
columnName: p.PropertyName,
header: p.ShortDisplayName
)));
This actually works like a charm (I was surprised it was that easy actually). What happens here is that from the properties of the model I use the ShortDisplayName as the column's header.
The problem? I need to apply a default format to all columns. Basically I want to use the Html.Raw extension for all the data that my grid will display. An attempt would be something like that :
var grid = new WebGrid(Model);
#grid.GetHtml(columns: ViewData.ModelMetadata.Properties.Single.Properties
.Select(p => grid.Column(
columnName: p.PropertyName,
header: p.ShortDisplayName,
format: (item) => Html.Raw(GetPropertyValue(item, p.PropertyName))
)));
where the method GetPropertyValue would read the value of the property using reflection or whatever (I need to remind here that item is dynamic and its value is actually the object that is being displayed in the current row).
Is there any better way to do this?
Thanks,
Kostas
I suggest you looking into MVCContrib Grid project: http://mvccontrib.codeplex.com/wikipage?title=Grid
Don't know if you still need some help with this question, but I had a problem just like yours and that's what I did to solve it:
I Used a Foreach loop to iterate through the properties
Filled a variable with the name of the property
Formated the column
The code that I got was something like this:
var columns = List<WebGridColumn>();
foreach (var p in ViewData.ModelMetadata.Properties.Single.Properties) {
String propertyName = p.PropertyName;
columns.Add(grid.Column(p.PropertyName, p.ShortDisplayName, format: item => Html.Raw(GetPropertyValue(item.Value, propertyName))));
}
#grid.GetHtml(columns: columns.ToArray());
And that's how I get the property's value:
public static object GetPropertyValue(object obj, String propertyName)
{
if (propertyName.Contains("."))
{
int index = propertyName.IndexOf(".");
object prop = obj.GetType().GetProperty(propertyName.Substring(0, index)).GetValue(obj, null);
return GetPropertyValue(prop, propertyName.Substring(index + 1));
}
return obj.GetType().GetProperty(propertyName).GetValue(obj, null);
}
I really don't know if this is the best way, but it's working pretty good for me.
Caveat: This might be an inappropriate use of C#'s dynamic keyword and I probably should be using a strongly-typed view model, but...
I'm trying to avoid creating a strongly-typed view model by passing a C# 4 dynamic type to my view. I have this in my controller:
public ActionResult Index()
{
var query =
from fr in db.ForecastRates
join c in db.Codes
on
new { Code = fr.RateCode, CodeType = "ForecastRate" }
equals
new { Code = c.CodeValue, CodeType = c.CodeType }
select new
{
RateCode = fr.RateCode,
RateCodeName = c.CodeName,
Year = fr.Year,
Rate = fr.Rate,
Comment = fr.Comment
};
// Create a list of dynamic objects to form the view model
// that has prettified rate code
var forecastRates = new List<dynamic>();
foreach (var fr in query)
{
dynamic f = new ExpandoObject();
f.RateCode = fr.RateCode;
f.RateCodeName = fr.RateCodeName;
f.Year = fr.Year;
f.Rate = fr.Rate;
f.Comment = fr.Comment;
forecastRates.Add(f);
}
return View(forecastRates);
}
...and this in my view (I'm using MVC 3's Razor view engine):
#inherits System.Web.Mvc.WebViewPage<IEnumerable<dynamic>>
...
<tbody>
#foreach (var item in Model) {
<tr>
<td>#item.RateCodeName</td>
<td>#item.Year</td>
<td>#item.Rate</td>
<td>#item.Comment</td>
</tr>
}
</tbody>
I don't like how I iterate through the LINQ result to form the List of dynamic objects.
I'd like to initialize each ExpandoObject inside the LINQ query, but that doesn't seem to be supported.
I tried casting the the query result as List, but that didn't work because you can't convert anonymous type to dynamic.
Like you said, it's not supported. (I'm not saying dynamic View Models aren't supported - I'm saying what you're trying to do is not)
You could probably neaten up the LINQ query, but in the end your best bet would be to simply create a custom View Model. Seriously, it will take you about 30 seconds to do that.
I know dynamic is new and cool and everything, but your code will be a lot neater and easier to maintain if you just stick with a custom View Model in this case.
I would only go with a dynamic View Model in the very simple scenarios - most of the time you probably want to stick with what we've been doing all along - custom View Models.
Ok, you could do the following, but I wouldn't recommend it. Create a static method similar to the following
public static IHtmlString DisplayProperty(object obj, string property) {
return new HtmlString(TypeDescriptor.GetProperties(obj)[property].GetValue(obj).ToString());
}
Then in your cshtml file make the following call (make sure to using your proper namespace)
<tbody>
#foreach (var item in Model) {
<tr>
<td>#DisplayProperty(x, "RateCodeName")</td>
<td>#DisplayProperty(x, "Year")</td>
<td>#DisplayProperty(x, "Rate")</td>
<td>>#DisplayProperty(x, "Comment")</td>
</tr>
}
</tbody>
I wouldn't recommend this though but it is a solution to your problem that doesn't require a model.
Say you're writing a web page for fruit vendors using Spring MVC's SimpleFormController, version 2.5.6. On this page the vendor can do simple things like change their name or their address. They can also change their inventory based on a drop down list filled with present inventory selections.
When this drop down list selection changes, the entire form changes to match the inventory of what has been selected. So one stock selection may have bananas and pears, another may have melons, blueberries and grapefruit.
Inside each inventory selection is a input field that needs to be propagated back to the database, for the sake of this example let's say that the user enters the number of fruit.
The way this is modeled in the database is that each Stock name is stored in a table, which has a one to many relationship with the contents of each stock, which would be the type of fruit in this example. Then the type of fruit has a one to many relationship with the quantity the vendor selects. Stock name and the type of fruit in each stock are stored in the database and are unchangeable by the user, with the connected fruit quantity table being editable.
My question is, how do you model the form described above in Spring MVC?
I've tried overriding the isFormChangeRequest and onFormChange to facilitate the form change, but I think I may be misunderstanding the intent of these methods. When I change my backing command object the next time the page is post it tries to bind the request into the form, which breaks if you adjust the size of the Stock array (say from 3 to 2, it will try and bind into the 3rd value, even if it is empty).
If you have a limited amount of different stocks, you can use different handler mappings for each one with a different backing model:
#RequestMapping(params="stock=example1")
ModelAndView handleExample1(#ModelAttribute("stock") ApplesOrangesPears stockObject)
#RequestMapping(params="stock=example2")
ModelAndView handleExample2(#ModelAttribute("stock") BananasPotatos stockObject)
But I guess that is not the case, there are a lot of different stock types and they are dynamic. In that case you can register custom property editor (#InitBinder), and determine dynamically the actual type of the backing object for the inventory, then validate, and convert to or from it explicitly.
What I ended up doing is firing a JavaScript event when the selection in the drop down is changed. This JavaScript (seen below) generates a URL based on the selection of the drop down and uses a location.replace to go to the new URL, which causes the controller to generate a new form.
Using this method over overriding the isFormChangeRequest and onFormChange has allowed me to avoid binding errors caused by left over post data.
function changeUrl(selectionValue) {
var param = getParams();
param["dropdownselection"] = selectionValue;
window.location.replace(getBaseUrl() + buildQueryString(param));
}
//taken from http://javascript.about.com/library/blqs1.htm
function getParams() {
var qsParm = new Array();
var query = window.location.search.substring(1);
var parms = query.split('&');
for (var i = 0; i < parms.length; i++) {
var pos = parms[i].indexOf('=');
if (pos > 0) {
var key = parms[i].substring(0,pos);
var val = parms[i].substring(pos+1);
qsParm[key] = val;
}
}
return qsParm;
}
function getBaseUrl() {
var url = document.location.toString();
if (url.indexOf('?') != -1) {
url = url.substring(0, url.indexOf('?'));
}
return url;
}
function buildQueryString(param) {
var queryString = "?";
for (var key in param) {
queryString += key + "=" + param[key] + "&";
}
//remove last "&"
return queryString.substring(0,queryString.length - 1);
}
I have two tables in my database connected by foreign keys: Page (PageId, other data) and PageTag (PageId, Tag). I've used LINQ to generate classes for these tables, with the page as the parent and the Tag as the child collection (one to many relationship). Is there any way to mark PageTag records for deletion from the database from within the Page class?
Quick Clearification:
I want the child objects to be deleted when the parent DataContext calls SubmitChanges(), not before. I want TagString to behave exactly like any of the other properties of the Page object.
I would like to enable code like the following:
Page page = mDataContext.Pages.Where(page => page.pageId = 1);
page.TagString = "new set of tags";
//Changes have not been written to the database at this point.
mDataContext.SubmitChanges();
//All changes should now be saved to the database.
Here is my situation in detail:
In order to make working with the collection of tags easier, I've added a property to the Page object that treats the Tag collection as a string:
public string TagString {
get {
StringBuilder output = new StringBuilder();
foreach (PageTag tag in PageTags) {
output.Append(tag.Tag + " ");
}
if (output.Length > 0) {
output.Remove(output.Length - 1, 1);
}
return output.ToString();
}
set {
string[] tags = value.Split(' ');
PageTags.Clear();
foreach (string tag in tags) {
PageTag pageTag = new PageTag();
pageTag.Tag = tag;
PageTags.Add(pageTag);
}
}
}
Basically, the idea is that when a string of tags is sent to this property, the current tags of the object are deleted and a new set is generated in their place.
The problem I'm encountering is that this line:
PageTags.Clear();
Doesn't actually delete the old tags from the database when changes are submitted.
Looking around, the "proper" way to delete things seems to be to call the DeleteOnSubmit method of the data context class. But I don't appear to have access to the DataContext class from within the Page class.
Does anyone know of a way to mark the child elements for deletion from the database from within the Page class?
After some more research, I believe I've managed to find a solution. Marking an object for deletion when it's removed from a collection is controlled by the DeleteOnNull parameter of the Association attribute.
This parameter is set to true when the relationship between two tables is marked with OnDelete Cascade.
Unfortunately, there is no way to set this attribute from within the designer, and no way to set it from within the partial class in the *DataContext.cs file. The only way to set it without enabling cascading deletes is to manually edit the *DataContext.designer.cs file.
In my case, this meant finding the Page association, and adding the DeleteOnNull property:
[Association(Name="Page_PageTag", Storage="_Page", ThisKey="PageId", OtherKey="iPageId", IsForeignKey=true)]
public Page Page
{
...
}
And adding the DeleteOnNull attribute:
[Association(Name="Page_PageTag", Storage="_Page", ThisKey="PageId", OtherKey="iPageId", IsForeignKey=true, DeleteOnNull = true)]
public Page Page
{
...
}
Note that the attribute needed to be added to the Page property of the PageTag class, not the other way around.
See also:
Beth Massi -- LINQ to SQL and One-To-Many Relationships
Dave Brace -- LINQ to SQL: DeleteOnNull
Sorry, my bad. That won't work.
It really looks like you need to be doing this in your repository, rather than in your Page class. There, you have access to your original data context.
There is a way to "attach" the original data context, but by the time you do that, it has become quite the code smell.
Do you have a relationship, in your Linq to SQL entity diagram, linking the Page and PageTags tables? If you don't, that is why you can't see the PageTags class from the Page class.
If the foreign key in the PageTags database table is set to Allow Nulls, Linq to SQL will not create the link when you drag the tables into the designer, even if you created a relationship on the SQL Server.
This is one of those areas where OR mapping can get kind of hairy. Providing this TagString property makes things a bit more convenient, but in the long run it obfuscates what is really happening when someone utilizes the TagString property. By hiding the fact that your performing data modification, someone can very easily come along and set the TagString without using your Page entity within the scope of a DataContext, which could lead to some difficult to find bugs.
A better solution would be to add a Tags property on the Page class with the L2S model designer, and require that the PageTags be edited directly on the Tags property, within the scope of a DataContext. Make the TagString property read only, so it can be genreated (and still provide some convenience), but eliminate the confusion and difficulty around setting that property. This kind of change clarifies intent, and makes it obvious what is happening and what is required by consumers of the Page object to make it happen.
Since Tags is a property of your Page object, as long as it is attached to a DataContext, any changes to that collection will properly trigger deletions or insertions in the database in response to Remove or Add calls.
Aaron,
Apparently you have to loop thru your PageTag records, calling DeleteOnSubmit for each one. Linq to SQL should create an aggregate query to delete all of the records at once when you call SubmitChanges, so overhead should be minimal.
replace
PageTags.Clear();
with
foreach (PageTag tag in PageTags)
myDataContext.DeleteOnSubmit(tag);
Aaron:
Add a DataContext member to your PageTag partial class.
partial class PageTag
{
DataClassesDataContext myDataContext = new DataClassesDataContext();
public string TagString {
..etc.
Larger code sample posted at Robert Harvey's request:
DataContext.cs file:
namespace MyProject.Library.Model
{
using Tome.Library.Parsing;
using System.Text;
partial class Page
{
//Part of Robert Harvey's proposed solution.
MyDataContext mDataContext = new TomeDataContext();
public string TagString {
get {
StringBuilder output = new StringBuilder();
foreach (PageTag tag in PageTags) {
output.Append(tag.Tag + " ");
}
if (output.Length > 0) {
output.Remove(output.Length - 1, 1);
}
return output.ToString();
}
set {
string[] tags = value.Split(' ');
//Original code, fails to mark for deletion.
//PageTags.Clear();
//Robert Harvey's suggestion, thorws exception "Cannot remove an entity that has not been attached."
foreach (PageTag tag in PageTags) {
mDataContext.PageTags.DeleteOnSubmit(tag);
}
foreach (string tag in tags) {
PageTag PageTag = new PageTag();
PageTag.Tag = tag;
PageTags.Add(PageTag);
}
}
}
private bool mIsNew;
public bool IsNew {
get {
return mIsNew;
}
}
partial void OnCreated() {
mIsNew = true;
}
partial void OnLoaded() {
mIsNew = false;
}
}
}
Repository Methods:
public void Save() {
mDataContext.SubmitChanges();
}
public Page GetPage(string pageName) {
Page page =
(from p in mDataContext.Pages
where p.FileName == pageName
select p).SingleOrDefault();
return page;
}
Usage:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(string pageName, FormCollection formValues) {
Page updatedPage = mRepository.GetPage(pageName);
//TagString is a Form value, and is set via UpdateModel.
UpdateModel(updatedPage, formValues.ToValueProvider());
updatedPage.FileName = pageName;
//At this point NO changes should have been written to the database.
mRepository.Save();
//All changes should NOW be saved to the database.
return RedirectToAction("Index", "Pages", new { PageName = pageName });
}