Is there an easy way, without looping over all the items in an array manually, to convert to a SelectList from an array of strings for a drop down menu?
I'm assuming you need either a SelectList or a List<SelectListTiem>, not a List<SelectList>. SelectList has a constructor that takes a collection:
string[] strings = new [] { .. strings .. };
SelectList sl = new SelectList(strings);
or you can project to a List<SelectListItem>:
string[] strings = new [] { .. strings .. };
var sl = strings.Select(s => new SelectListItem {Value = s})
.ToList();
Note that SelectList implements IEnumerable<SelectListItem>, so if you have a model property of type IEnumerable<SelectListItem> you can create a SelectList and assign it to that property rather than projecting to a List<SelectListItem>. It's functionally the same but the code will be a little cleaner.
This is all assuming we're talking about MVC, not Web Forms
Second to D Stanley's answer, another solution:
string[] strings = new [] { ... strings ... };
var selectListItems = strings.Select(x => new SelectListItem() { Text = x, Value = x, Selected = x == "item 1" });
A list of SelectListItem can also be used to populate an MVC drop down list.
With this method, you can also set other properties on a SelectListItem such as, display value.
We can't call Select on a IQueryable using the SelectListItem constructor because LINQ will try and convert that to SQL. Which unless there is a provider for it, is impossible, and also not what we want to achieve.
In order to always assure we can enumerate like I have shown above, we need to force EF or other ORMs to get all our data back. We can do this by calling ToList() BEFORE we enumerate with Select:
var selectListItems = strings.ToList().Select(x => new SelectListItem() { Text = x, Value = x, Selected = x == "item 1" });
As #BCdotWEB has pointed out:
public SelectList(
IEnumerable items,
string dataValueField,
string dataTextField
)
Is the constructor that this list will inevitably get put into. If I can remember correctly, the razor view should look like this:
#Html.DropDownListFor(x => x.SelectedString, new SelectList(x.Strings, "Value", "Text"))
Where x.SelectedString is where you want the chosen value from the drop down to be put. x.Strings is that selectListItems we created in the Controller/Service
I assume you can use the SelectList Constructor, since it accepts an IEnumerable:
public SelectList(
IEnumerable items,
string dataValueField,
string dataTextField
)
if you are talking about asp.net webForms you can use this code
string[] stringArray= new []{"var1",...};
Dictionary<string,string> listItemSource=stringArray.ToDictionary(i => i, i =>i);
yourDropDownList.DataSource=listItemSource;
yourDropDownList.DataValueField = "value";
yourDropDownList.DataTextField = "key";
yourDropDownList.DataBind();
Related
I need to create a dropdown list and I'm doing this by creating a new SelectList based on a model. Here is how I am trying to do this:
#Html.DropDownListFor(model=>model.SelectedStudio, new SelectList(Model.Studios, "Id", "Name", Model.Studio)
I see from the class signature that the last parameter is object selectedValue. I have now tried many variations, trying to pass a string there, an object, etc. but when I compile the program, the selected value for the dropdown list is never set to what I want.
Can anyone explain how this works?
EDIT: I don't know if this is important, but the Id of Studio is of type ObjectId (from the MongoDB C# Driver)
I think your not setting for the selected value on new SelectList
your code should be
#Html.DropDownListFor(model=>model.SelectedStudio, new SelectList(Model.Studios, "Id", "Name", [Defualt value])
the reason it not give the error becuase it is object. and your setting up your IEnumerable list. so it is object. see the following link
http://msdn.microsoft.com/en-us/library/dd492553(v=vs.118).aspx
Try this:
#Html.DropDownListFor(model=>model.SelectedStudio, new SelectList(Model.Studios, "Id", "Name", Model.Studio.Id)
this is how u keep a value selected in drop down
#Html.DropDownList("statussearch", new List<SelectListItem>
{
new SelectListItem { Text = "text1", Value = "1", Selected = Studio.IsSelected.HasValue ? Studio.IsSelected.Value : false},
new SelectListItem { Text = "text2", Value = "2"},
new SelectListItem { Text = "text3", Value = "3"},
}, "Select Status")
IsSelected is a field in your DB wch states wch value to be selected.
this will work fine for your requirement
#foreach (var value in studios)
{ #Html.DropDownList("statussearch", new List<SelectListItem>
{new SelectListItem { Text =value.prop1, Value = "1" },new SelectListItem { Text = value.prop2, Value = "2"},new SelectListItem { Text = value.prop3, Value = "3"},}, value.proptobeselected)}
I am still reasonably new to C# and trying to understand list objects.
I have a list object with key/value pairs in it, populated from a database (that part is working). I then want to select a value from that list, using the 'key'. From what I have read I think Linq might be the best way to do this, however I cannot quite work out the syntax I need.
I have a list object as follows:
// Create a list of Items from the database, where Value is the 'key' and Text is the 'value'
IEnumerable<SelectListItem> ItemList = dbLists.ItemList.Select(x => new SelectListItem { Text = x.Description, Value = x.Id.ToString() });
I then want to populate another variable with the description of the selected item in the model, where the model only saves the id.
I have tried various linq Where and Select queries, but cannot work it out.
The easiest way I can think to explain what I am trying to achieve is to use sql syntax,
string SelectedItemDescription = SELECT Text FROM ItemList WHERE ItemList.Value = model.ItemCode
An example of a scenario would be something like:
ItemList
{
(Value = "1", Text = "Item 1"),
(Value = "2", Text = "Item 2"),
(Value = "3", Text = "Item 3"),
...
};
model.ItemCode = 2;
// How do I make:
SelectedItemDesctiption = "Item 2";
Hopefully that makes sense..
Thanks.
you can do like this in LINQ, if you write it this way:
string SelectedItemDescription = (from list in ItemList
where list.Value = model.ItemCode
select list.Text).FirstOrDefault();
or you can Use Extension Methods, If it will always return a single element then you can use SingleOrDefault():
SelectListItem SelectedItemDescription = ItemList.SingleOrDefault(item=>item.Value == model.ItemCode);
if(SelectedItemDescription !=null)
{
string Key = SelectedItemDescription .Value;
string Text = SelectedItemDescription.Text;
}
If it will return a multiple objects then you can use FirstOrDefault():
SelectListItem SelectedItemDescription = ItemList.FirstOrDefault(item=>item.Value == model.ItemCode);
if(SelectedItemDescription !=null)
{
string Key = SelectedItemDescription .Value;
string Text = SelectedItemDescription.Text;
}
UPDATED:
As #CodeGeek suggested in comments, you can also do like this:
string SelectedItemDescription =ItemList
.SingleOrDefault(item=>item.Value == model.ItemCode)!=null ? ItemList.SingleOrDefault(item=>item.Value == model.ItemCode).Text : String.Empty;
I have the following select list
public SelectList StaffList { get; set; }
I am assigning it the following,
inspectorCorrespondences.StaffList = new SelectList(userDetails, "Id", "FullName");
but I want to add in another SelectList item
var systemGeneratedUser = new SelectListItem() { Value = "-1", Text = "System Generated" };
how do I do that?
This isn't necessarily the most elegant solution, but you'll need to cast the SelectList's items to a list of SelectListItems if you want to add another SelectListItem.
var myItems = new List<SelectListItem>();
myItems.Add(new SelectListItem() { Text = "AA", Value = "11" } );
var mySelectList = new SelectList(myItems);
((List<SelectListItem>)mySelectList.Items).Add(new SelectListItem() { Text = "BB", Value = "22" });
According to the documentation, it looks like you need to initialize the SelectList with the values instead of adding them. Passing an enumerable of SelectListItem to the constructor appears to be the expected way.
It looks like you're already doing that in the sense that userDetails is already an enumeration? If so, what type of enumeration is it? You may need to add a line or two of code to transform it to an enumeration of SelectListItem objects, add yours to that, and then use that to initialize the SelectList. Maybe something like this:
var listItems = userDetails.Select(u => new SelectListItem { Value = u.Id, Text = u.FullName }).ToList();
listItems.Add(new SelectListItem() { Value = "-1", Text = "System Generated" });
// or perhaps .Insert() at position 0 instead?
inspectorCorrespondences.StaffList = new SelectList(listItems, "Value", "Text");
I have a class named DataAPIKey. I have a second class which inherits from that one.
In my code I have a List, and I would like to use that to make a list of the new class. Is there any way to do this without using a for each loop?
Using the example below I made the following code which seems to be doing what I want.
List<DataAPIKey> apiList = db.GetPendingAction("Character");
List<DataCharacter> charList = apiList.Select(k => {
DataCharacter dc = new DataCharacter(k.apiKeyId, k.keyId, k.verificationCode);
return dc;
}).ToList()
Use the LINQ Select method.
var newList = oldList.Select(oldItem => new InheritedItem(oldItem)).ToList();
In plain English this translates to "Take each item from oldList, feed each as a function parameter to a function which will take that item and perform some logic to return a different type of item, then take all the returned items and populate them into a new List."
Or if you don't have a constructor to initialize the inherited class then you can provide any code block:
var newList = oldList.Select(oldItem =>
{
var newItem = new InheritedItem();
newItem.Property = oldItem.Property;
return newItem;
}).ToList();
Or an initializer:
var newList = oldList.Select(oldItem => new InheritedItem()
{
Property = oldItem.Property,
Property2 = oldItem.Property2
}).ToList();
I need to convert a select list (which is populated by a data feed) into lower case, I have traced as far some code in the relevant controller;
private SelectList getAddressCountriesListDD()
{
var addressCountries = myOPG.AddressCountries;
return new SelectList(addressCountries, "key", "value", "GBR");
}
The myopg part is the datafeed, I need to get the selectlist into lowercase.
How can I accomplish this?
Replace
var addressCountries = myOPG.AddressCountries;
with
var addressCountries = myOPG.AddressCountries
.Select(c => c.ToString().ToLowerInvariant());
if addressCountries is a list of strings, then something like this (using LINQ).....
var lcase = from c in addressCountries
select c.ToLower();