Xamarin Tabbed Page error Error "The given key was not present"

Question

I created a new blank Xamarin PCL app in Visual Studio 2015. It runs on all the platforms. I then add a XAML page named GuyBarSceneTabs to my PCL and change my app.cs file in my PCL so the App() code only contains

MainPage = new GuyBarSceneTabs();

This all works and I can run the projects again and it shows my XAML page. Next I add another XAML page name NearbyLocations

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="GuyBarScene.NearbyLocations"
             Title= "Nearby Locations">

</ContentPage>

I also then change the GuyBarSceneTabs page to be a tabbed page as follows and also change the code behind page to inherit from TabbedPage:

<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage xmlns="http://xamarin.com/schemas/2014/forms"
            xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
            xmlns:local="clr-namespace:GuyBarScene;assembly=GuyBarScene"
            x:Class="GuyBarScene.GuyBarSceneTabs">    
    <TabbedPage.Children>        
        <local:NearbyLocations  />         
    </TabbedPage.Children>
</TabbedPage>       
        
</TabbedPage.Children>

public partial class GuyBarSceneTabs : TabbedPage
{
    public GuyBarSceneTabs()
    {
        InitializeComponent();
    }
}

Now when I try to run the app I get the error message: "The given key was not present in the dictionary. There error is generated in the following code which is called from the InitializeComponent method of GuyBarSceneTabs page:

public partial class GuyBarSceneTabs : global::Xamarin.Forms.TabbedPage {

    [System.CodeDom.Compiler.GeneratedCodeAttribute("Xamarin.Forms.Build.Tasks.XamlG", "0.0.0.0")]
    private void InitializeComponent() {
        this.LoadFromXaml(typeof(GuyBarSceneTabs));
    }
}

Any suggestions as to what I am doing wrong? Do I need to change my App() code in some manner?

Is it an copy and paste error? Else there is a extra `` at the end of your XAML page. Also this seems like a bug in older versions of Xamarin.Forms. Which version are you using? — Gerald Versluis, Sep 29 '16 at 06:31
Sorry that is a copy and paste error. Also I am using the latest version of Xamarin form according to Nuget - version 2.3.2.127 — George M Ceaser Jr, Sep 29 '16 at 11:53

score 2 · Answer 1 · answered Apr 24 '17 at 18:45

2

My story is similar but has a different solution so I thought I'd add it here for posterity. I had an existing View which received a ViewModel as a parameter. When I included it as one of the I got the "The given Key was not present" error. Upon rewriting the View without passing in parameters, then it worked.

answered Apr 24 '17 at 18:45

will.itrax

58
1
9

2

That was exactly my problem. And this is once again proves the early development phase of Xamarin, given what cryptic error messages you get for totally unrelated problems. :( – Exa Apr 26 '17 at 13:02
I still came across this "The given Key was not present" error today (a year later) so I have less hope of it becoming much better. – Paul May 02 '18 at 00:25

score 0 · Accepted Answer · answered Oct 01 '16 at 22:07

So I figured this out. This problem appears to manifest if you rename a XAML and corresponding cs file in your project. It appears something gets messed up in the project file. The easiest thing to do is add a new XAML page with a new name and copy things from the old XAML file to the new file. Then it appears to work. In my case, the problem was caused by renaming the XAML page the inherited from TabbedPage file. Hope this helps anyone else who has this problem.

FYI the problem can also manifest itself if you include a XAML page and cs file from an other project and them rename them. In this case, when the project file gets messed up you will get an error that the InitializeComponent method does not exist will be thrown.

I have to say I REALLY want Xamarin to work well. I hope now that it is owned by MS it becomes more of a reliable, first tier development solution.

score 0 · Answer 3 · answered Oct 28 '17 at 08:56

0

In my case key of the problem - default parameterless constructor was modified (added parameter).

After default constructor was added again - compilation error gone.

answered Oct 28 '17 at 08:56

ydanila

435
1
5
11

score 0 · Answer 4 · answered Nov 27 '17 at 11:45

in my case i was making custom map control and write new constructor which is different from the default one to fix this issue i had to have both constructors

        public SAMap()  
        {

        }

        public SAMap(MapSpan region)  
        {

        }

Xamarin Tabbed Page error Error "The given key was not present"

4 Answers4