ASP.NET MVC Select list value using key

Question

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.

Ehsan Sajjad · Accepted Answer · 2014-06-05 04:29:21Z

3

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;

edited Jun 5, 2014 at 4:29

answered Jun 4, 2014 at 5:58

Ehsan Sajjad

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8 Comments

David Pilkington Over a year ago

Your code will throw a null reference exception if that item is not in the list

Arijit Mukherjee Over a year ago

string SelectedItemDescription = ItemList.SingleOrDefault(item=>item.Value == model.ItemCode).Text; will do it straight

Ehsan Sajjad Over a year ago

@DavidPilkington i am using SingleOrDefault

David Pilkington Over a year ago

@EhsanSajjad from MSDN on SingleOrDefault "a default value if the sequence is empty" the default of his object is most likely null

Ehsan Sajjad Over a year ago

yes you are right i added null check @DavidPilkington updated

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