According to http://msdn.microsoft.com/en-us/library/dd470803.aspx, the MultiSelectList(IEnumerable, IEnumerable) constructor takes in two parameters: items and selectedValues.
The documentation is not completely explicit so I just want to clarify two points:
How exactly does selectedValues work? Does this constructor merely iterate through the collection and set .Selected = True for each element?
Must selectedValues be a subset of items? How is this defined, precisely (i.e. as long as their ToString values match)?
Specifically, I am playing with a jQuery multiselect plugin and am trying to do essentially what is being done in the demo of that plugin (i.e. the "selected" list is already populated by certain elements upon initialization).
The HTML:
<%=Html.ListBoxFor(model => model.tempCategories, (MultiSelectList)(ViewData["Categories"]), new {#size = "5" })%>
Controller code:
List<Categories> categoriesList = categories.Select();
ViewData["Categories"] = GenCategoryMultiList(categoriesList);
private System.Web.Mvc.MultiSelectList GenCategoryMultiList(List<TemplateCategories> entity)
{
entity = entity.OrderBy(e => e.CategoryName).ToList();
System.Web.Mvc.MultiSelectList selectList = new System.Web.Mvc.MultiSelectList(entity, "CategoryID", "CategoryName");
return selectList;
}
I am using this with JQuery Multiselect. Working code...
Related
In the example bot implementations from Microsoft, they use enums to define options for dialog, as shown in the example below:
public enum LengthOptions { SixInch, FootLong };
public enum BreadOptions { NineGrainWheat, NineGrainHoneyOat, Italian, ItalianHerbsAndCheese, Flatbread };
Can we use a normal list to fetch the values from the database and display it as options?
Thanks
You can't do this out of the box, but you could subclass FormBuilderBase<T>, overriding various methods to build the Form using whatever datasource you prefer.
Edit:
You can find the base class and implementation of FormBuilder here: https://github.com/Microsoft/BotBuilder/blob/master/CSharp/Library/FormFlow/FormBuilder.cs
Basically, there are a mess of virtual methods that you can override to customize how you want to form to behave, but the main one is Build. In the default implementation, it iterates though the enums to create a list of Field, which are basically each step in you form. Instead of that, you can iterate through whatever data you have pulled from your database and create a new Field for each item. It may look something like this:
public override IForm<T> Build(Assembly resourceAssembly = null, string resourceName = null)
{
var list = GetListOfItemsFromDatabase();
foreach (var item in _list)
{
// FieldFromItem is an IField and will also need to be created
Field(new FieldFormItem<T>(item));
}
Confirm(new PromptAttribute(_form.Configuration.Template(TemplateUsage.Confirmation)));
}
return base.Build(resourceAssembly, resourceName);
}
I know its late but found myself struggling with the same and found that below would be the right solution for this.In your FormFlow class just add the Terms and Descriptions manually.From your example if we are talking about length options then change the type of LengthOptions to string add following code when you build the form.
return new FormBuilder<SandwichForm>()
.Field(new FieldReflector<SandwichForm>(nameof(LengthOptions))
.SetDefine(async (state, field) =>
{
// Call database and get options and iterate over the options
field
.AddDescription("SixInch","Six Inch")
.AddTerms("SixInch", "Six Inch")
.AddDescription("FootLong ","Foot Long")
.AddTerms("FootLong ", "Foot Long")
return true;
}))
.OnCompletion(completionDelegate)
.Build();
I tried to use Distinct() to filter my collection to prevent duplication but my linq query still adds the same values to list.
thanks in advance.
public ObservableCollection<string> CollectTopicsFromXml()
{
ObservableCollection<string> oc = new ObservableCollection<string>();
XDocument xDoc = XDocument.Load(path);
var topicColl = xDoc.Descendants("topic").Distinct();
foreach (var topic in topicColl)
{
oc.Add(topic.Value);
}
return oc;
}
Distinct by default uses reference equality unless Equals (and GetHashCode) are overridden on the item type. Since Equals is not overridden for XElement each element is "distinct" regardless of its contents.
If you want distinct elements by Name or some other property (or combination of properties) you have a few options:
Project the elements to an anonymous type which does implement value equality by default:
var topicColl = xDoc.Descendants("topic")
.Select(e => new {e.Name, e.Value})
.Distinct();
Use GroupBy, which allows an expression to be passed in
Create a class that implements IEqualityComparer<XElement> in the way that you want and pass that to Distinct
Use DistinctBy from MoreLinq which also allows an equality expression to be passed in
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.
I am developing an ASP.NET MVC3 application in C#.
I am trying to implement in my application a "narrow-down" functionality applied the result-set obtained from a search.
In short, after I perform a search and the results displayed in the center of the page, I would like to have on the left/right side of the page a CheckBoxList helper for each property of the search result. The CheckBox of each CheckBoxList represent the distinct values of the property.
For instance if I search Product and it has a Color property with values blue, red and yellow, I create a CheckBoxList with text Color and three CheckBox-es one for each color.
After a research on the Web I found this Dynamic LINQ library made available by Scott Guthrie. Since the most recent example/tutorial I found is from 2009, I was wondering whether this library is actually good (and maintained) or not.
In the latter case is jQuery the best way to implement such functionality?
You can solve it by building the needed predicate expressions dynamically, using purely .NET framework.
See code sample below. Depending on the criteria, this will filter on multiple properties. I've used IQuerable because this will enable both In-Memory as remote scenario's such as Entity Framework. If you're going with Entity Framework, you could also just build an EntitySQL string dynamically. I expect that will perform better.
There is a small portion of reflection involved (GetProperty). But this could be improved by performing caching inside the BuildPredicate method.
public class Item
{
public string Color { get; set; }
public int Value { get; set; }
public string Category { get; set; }
}
class Program
{
static void Main(string[] args)
{
var list = new List<Item>()
{
new Item (){ Category = "Big", Color = "Blue", Value = 5 },
new Item (){ Category = "Small", Color = "Red", Value = 5 },
new Item (){ Category = "Big", Color = "Green", Value = 6 },
};
var criteria = new Dictionary<string, object>();
criteria["Category"] = "Big";
criteria["Value"] = 5;
var query = DoDynamicWhere(list.AsQueryable(), criteria);
var result = query.ToList();
}
static IQueryable<T> DoDynamicWhere<T>(IQueryable<T> list, Dictionary<string, object> criteria)
{
var temp = list;
//create a predicate for each supplied criterium and filter on it.
foreach (var key in criteria.Keys)
{
temp = temp.Where(BuildPredicate<T>(key, criteria[key]));
}
return temp;
}
//Create i.<prop> == <value> dynamically
static Expression<Func<TType, bool>> BuildPredicate<TType>(string property, object value)
{
var itemParameter = Expression.Parameter(typeof(TType), "i");
var expression = Expression.Lambda<Func<TType, bool>>(
Expression.Equal(
Expression.MakeMemberAccess(
itemParameter,
typeof(TType).GetProperty(property)),
Expression.Constant(value)
),
itemParameter);
return expression;
}
}
I don't really get why would you need the Dynamic LINQ here? Are the item properties not known at compile-time? If you can access a given item properties by name, eg. var prop = myitem['Color'], you don't need Dynamic LINQ.
It depends on how you render the results. There is a lot of ways to achieve the desired behavior, in general:
Fully client-side. If you do everything client-side (fetching data, rendering, paging) - jQuery would be the best way to go.
Server-side + client-side. If you render results on the server, you may add HTML attributes (for each property) to each search result markup and filter those client-side. The only problem in this case can be paging (if you do paging server-side, you will be able to filter the current page only)
Fully server-side. Post the form with search parameters and narrow down the search results using LINQ - match the existing items' properties with form values.
EDIT
If I were you (and would need to filter results server-side), I'd do something like:
var filtered = myItems.Where(i => i.Properties.Match(formValues))
where Match is an extension method that checks if a given list of properties matches provided values. Simple as this - no Dynamic LINQ needed.
EDIT 2
Do you need to map the LINQ query to the database query (LINQ to SQL)? That would complicate things a bit, but is still doable by chaining multiple .Where(...) clauses. Just loop over the filter properties and add .Where(...) to the query from previous iteration.
you may have a look at PredicateBuilder from the author of C# 4.0 in a Nutshell
As already pointed out by #Piotr Szmyd probabbly you don't need dynamic Linq. Iterating over all properties of T doesn'require dynamic linq. Dynamic Linq is mainly usefull to build complete queries on the client side and send it in string format to the server.
However now, it become obsolete, since Mvc 4 supports client side queries through Api Controllers returning an IQueryable.
If you just need to iterate over all properties of T you can do it with reflection and by building the LambdaExpressions that will compose the filtering criterion. You can do it with the static methods of the Expression class.
By using such static methods you can build dynamically expressions like m => m.Name= "Nick" with a couple instructions...than you put in and them...done you get and expression you can apply to an exixting IQueryable
LINQ implementation still has not changed so there should be no problem using the dynamic LINQ library. It simply creates LINQ expressions from strings.
You can use AJAX to call action methods that run the LINQ query and return JSON data. JQuery would populate HTML from the returned data.
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.