Xamarin Can't Access Controls on Code Behind

Question

For my Xamarin Forms project (latest version 1.3), when I create a view in Xamarin Studio (latest, 5.5.4), I define the view as the following:

<?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="FormsDemo.Register">
  <ContentPage.Content>

    <Grid>
      <Grid.RowDefinitions>
        <RowDefinition />
        <RowDefinition />
        <RowDefinition />
        <RowDefinition />
      </Grid.RowDefinitions>
      <Grid.ColumnDefinitions>
        <ColumnDefinition Width="100" />
        <ColumnDefinition />
      </Grid.ColumnDefinitions>

      <Label Grid.Row="0" Grid.Column="0" Text="First Name" />
      <Entry x:Name="FirstName" Grid.Row="0" Grid.Column="1" />

      <Label Grid.Row="1" Grid.Column="0" Text="Last Name" />
      <Entry x:Name="LastName" Grid.Row="1" Grid.Column="1" />

      <Label Grid.Row="2" Grid.Column="0" Text="Email" />
      <Entry x:Name="Email" Grid.Row="2" Grid.Column="1" />

      <Button x:Name="SaveButton" Grid.Row="3" Grid.Column="0" Text="Login" />
    </Grid>

  </ContentPage.Content>
</ContentPage>

However, in my code-behind, any references to the control by its name are not being found at all. The following code is erroring (noted by comments):

using System;
using System.Collections.Generic;
using Xamarin.Forms;

namespace FormsDemo
{ 
  public partial class Register : ContentPage
  { 
    public Register ()
    {
      InitializeComponent ();

            //Using this approach worked, but is not ideal
      this.FindByName<Button>("SaveButton").Clicked += Save_Clicked;
    }

    void Save_Clicked (object sender, EventArgs e)
    {
      this.FirstName.Text = "A";
      this.LastName.Text= "B";
    }
  }
}

Oddly enough, I was getting warnings with:

Warning: The private field `FormsDemo.Register.FirstName' is assigned but its value is never used (FormsDemo.Solution)

I get one for each field. Why is this not working? How do I get IntelliSense to work?

Answer 1

The latest update seemed to fix the issue; these references works OK:

this.FirstName.Text = "A";
this.LastName.Text= "B";

It appears some of the designer problems are resolved.

Answer 2

you can try this

var asdf = this.FindByName<TimePicker>("tagName");

there are SUGGESTIONS to do here:

https://forums.xamarin.com/discussion/25409/problem-with-xaml-x-name-and-access-from-code-behind

DIRECT ANSWER from that link

On your page properties check the following properties are set:

BuildAction = Embedded Resource CustomTool = MSBuild:UpdateDesignTimeXaml

If that's okay, delete the obj & bin folders are rebuild the PCL.

If you import a XAML page into a PCL for example the attributes get changed and it won't compile.

Answer 3

I had a similar issue, In my case it was my own doing, In the xaml file, I had set the content attribute x:Class with the wrong value.

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         x:Class="**{namespace.classname}**">

Specifying the class name correctly solved the issue for me.

Answer 4

I had the same problem, after I renamed some files and manually corrected the Class references. Somehow VS was not able to find the references from xaml page. When I created new xaml file with code behind, the same code worked.