(Universal Windows App) System.NullReferenceException: Object reference not set to an instance of an object

Question

When i try to run very simple universal windows app it pops the exception above. I tried several times to fix it but it is still there. I am really new in programming so I will be very glad if someone can help. This is the design of my main page:

<UserControl x:Class="simpleCalc.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Test_App"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
d:DesignHeight="300" d:DesignWidth="400">

    <Grid x:Name="LayoutRoot" Background="#FFE2D7CC">
    <TextBlock x:Name="textBlock" HorizontalAlignment="Left" Margin="13,50,0,0" Text="Километри" 
TextWrapping="Wrap" VerticalAlignment="Top" Height="31" Width="114" FontFamily="Times New Roman" 
FontSize="22" FontWeight="Bold"
FontStyle="Italic"/>
    <TextBlock x:Name="textBlock1" HorizontalAlignment="Left" Margin="36,103,0,0" Text="Литри" 
TextWrapping="Wrap" VerticalAlignment="Top" Height="32" Width="114" FontFamily="Times New Roman" 
FontSize="22" FontWeight="Bold"
FontStyle="Italic"/>
    <TextBlock x:Name="textBlock2" HorizontalAlignment="Left" Margin="16,147,0,0" Text="Консумация" 
TextWrapping="Wrap" VerticalAlignment="Top" Height="31" Width="114" FontFamily="Times New Roman" 
FontSize="22" FontWeight="Bold"
FontStyle="Italic"/>
    <TextBox x:Name="mileage" HorizontalAlignment="Left" Height="28" Margin="149,47,0,0" 
TextWrapping="Wrap" Text="100" VerticalAlignment="Top" Width="120" Background="#FFD6F6F9"/>
    <TextBox x:Name="liters" HorizontalAlignment="Left" Height="31" Margin="149,97,0,0" 
TextWrapping="Wrap" Text="10" VerticalAlignment="Top" Width="120" Background="#FFD2EFF1"/>
    <TextBox x:Name="cons" HorizontalAlignment="Left" Height="27" Margin="149,145,0,0" 
TextWrapping="Wrap" Text="10" VerticalAlignment="Top" Width="120" Background="#FFC5EAEE"/>
    <TextBlock x:Name="textBlock3" HorizontalAlignment="Left"
Margin="274,147,0,0" TextWrapping="Wrap" Text="1/100 km" VerticalAlignment="Top"/>


    <Button x:Name="button1" Content="ИЗЧИСЛИ" HorizontalAlignment="Left"
Margin="149,199,0,0" VerticalAlignment="Top" Width="120" Click="Button_Click"
Height="35" Foreground="#FF3A2121" Background="#FFF32424">
        <Button.BorderBrush>
            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                <GradientStop Color="#FFA3AEB9" Offset="0"/>
                <GradientStop Color="#FF8399A9" Offset="0.375"/>
                <GradientStop Color="#FF718597" Offset="0.375"/>
                <GradientStop Color="#FFEE3760" Offset="1"/>
            </LinearGradientBrush>
        </Button.BorderBrush>
    </Button>
</Grid>

</UserControl>

And here is functional code:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

namespace simpleCalc
{
    public partial class MainPage : UserControl
    {
       public MainPage()
        {
        InitializeComponent();
        }
    private void Button_Click(object sender, RoutedEventArgs e)
    {
        double dMileage = Double.Parse(mileage.Text);
        double dLiters = Double.Parse(liters.Text);
        double dRes = 100 * (dLiters/dMileage);
        cons.Text = dRes.ToString("##.##");
    }
}

} When I run the app (simple calc for fuel in this case) it throws the exception here:

if (e.PrelaunchActivated == false)
        {
            if (rootFrame.Content == null)
            {
                ***rootFrame.Navigate(typeof(MainPage), e.Arguments);***
            }

I think it is because your MainPage is of type UserControl .. Try to add a new ContentPage instead of UserControl. — puko, Dec 14 '20 at 15:48

score 0 · Accepted Answer · answered Dec 14 '20 at 15:54

0

I think it is because your MainPage is of type UserControl .. Try to add a new ContentPage instead of UserControl.

answered Dec 14 '20 at 15:54

puko

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(Universal Windows App) System.NullReferenceException: Object reference not set to an instance of an object

1 Answers1