How to add new item to the x:Array from Window.Resources programmatically

Question

I have this XAML code:

<Window.Resources>
    <x:Array x:Name="arrayXAML" x:Key="WordList" Type="sys:String">
      <sys:String>Abraham</sys:String>
      <sys:String>Xylophonic</sys:String>

      <sys:String>Yistlelotusmoustahoppenfie</sys:String>
      <sys:String>Zoraxboraxjajaja</sys:String>
    </x:Array>
</Window.Resources>

I know that I can access this array by both of these lines of c#:

Object res1 = this.Resources["WordList"];
wordList = this.FindResource("WordList") as string[];

But what about if I want to add a new string to the x:Array programmatically?

I have tried: arrayXAML.Items.Add("hello"); but it doesn't seem to work when I then use the "FindRescource" as shown above. Is there a way to add items to this array?

You could instead use an observablecollection social.technet.microsoft.com/wiki/contents/articles/… — Andy
– Andy, Commented Apr 8, 2019 at 13:24

Rekshino · Accepted Answer · 2019-04-08 13:21:18Z

2

In XAML x:Array is represented with ArrayExtension class.

See x:Array on MSDN:

In the .NET Framework XAML Services implementation, the handling for this markup extension is defined by the ArrayExtension class.

It is important to understand, that what you have/get in/from your ResourceDictionary is not an ArrayExtension but string[].
So run-time changes on arrayXAML you will not see in the ResourceDictionary.

You can't add new element to the string[], see link, but what you can is to set new value in the ResourceDictionary for key WordList:

var sarr = this.Resources["WordList"] as string[];
var newSarr = new string[sarr.Length+1];
for (int i = 0; i < sarr.Length; i++)
{
    newSarr[i] = sarr[i];
}

newSarr[newSarr.Length-1] = "New string from code behind";          
this.Resources["WordList"] = newSarr;

Remark: Since you are modifing the resource, then do use a DynamicResource:

<ListBox ItemsSource="{DynamicResource WordList}"/>

edited Apr 8, 2019 at 13:21

answered Apr 8, 2019 at 13:14

Rekshino

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4 Comments

Rekshino Over a year ago

@mm8 You can't add an element to the existing instance of array. Resize method creates new instance and copy elements to it. Just not with for loop.

Rekshino Over a year ago

Your are wrong. See source code

mm8 Over a year ago

You are absolutely correct. It does create a copy. My bad. (+1)

Rekshino Over a year ago

@mm8 I admit, that it is a vile trap with changing only of the local variable by Array.Resize.

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