Content is set more than once

Question

Whilst playing about with WPF in Visual Studio 2013, I have been presented with an error:

Error 2 The property 'Content' is set more than once.

Error 1 The property "Content" can only be set once

Now, first of all. I turn to google for the error message & got presented with a top results linking to StackOverflow.

XAML - The property 'Content' is set more than once

the property 'Content' is set more than once

Property content is set more than once

Including a MSDN post:

http://social.msdn.microsoft.com/Forums/vstudio/en-US/686be076-954f-4373-a2e6-fc42a6a27718/error-the-property-content-is-set-more-than-once?forum=wpf

Whilst being presented with an informative collection of tailored solutions based on the original posters code, I have yet to come across an actual basic solution detailing the reasons of this error (XAML Novice) Whilst this may be a duplicate of multiple reported problems. I personally would rather avoid posting a problematic code to get a tailored solution. I'd much rather come here and ask the community reasons as to why a novice XAMP/WPF Developer might encounter this application and solutions & not so much top, top best practices. Rather words of advice from the more WPF/XAMP Developers on how to easily identify the solution and continue on with furter debugging steps in the future

---

For argument sake:

<Window x:Class="WPFT.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="197.198" Width="427.95">
    <TextBlock>Hello</TextBlock>
    <TextBlock>World</TextBlock>
</Window>

Answer 1

A window can only contains 1 element.

In your code

<Window x:Class="WPFT.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="197.198" Width="427.95">
    <TextBlock>Hello</TextBlock>
    <TextBlock>World</TextBlock>
</Window>

your window have 2 textblock u shoudl try something like

<Window x:Class="WPFT.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="197.198" Width="427.95">
    <Grid>
        <TextBlock>Hello</TextBlock>
        <TextBlock>World</TextBlock>
    </Grid>
</Window>

Answer 2

If you are setting more than one element inside of any UIElement with the Content dependency property, you will get this error. You need to wrap multiple elements inside of a panel so that the Content property only has one child element. For instance...

<Button>
    <StackPanel Orientation="Horizontal">
        <Image />
        <TextBlock />
    </StackPanel>
</Button>

<Border>
    <StackPanel>
        <TextBlock />
        <Image />
        <DatePicker />
    </StackPanel>
</Border>

The areas between the Button and Border elements are shorthand for specifying:

<Button>
    <Button.Content>
        <!-- Content goes here -->
    </Button.Content>
</Button>