Difference between x:Key and x:Name

Question

What is the difference between x:Key and x:Name in WPF?

Answer 1

x:Key is only valid inside a resource dictionary and is added to a dictionary, x:Name is used locally and represents a variable within the class.

Answer 2

x:Name is used to name UI elements (e.g. Controls, Panels etc), whereas x:Key is used to identify resources (which can be more or less anything) within a ResourceDictionary.

This means that you can't reference things in a resource dictionary using an x:Name value:

 <Grid>
    <Grid.Resources>
        <Style x:Name="StyleName" x:Key="StyleKey" />
    </Grid.Resources>
    <Button Style="{StaticResource StyleName}" /> <!-- Will not work-->
    <Button Style="{StaticResource StyleKey}" /> <!-- Will work -->
</Grid>

You will also notice that elements that are not within a resource dictionary cannot have an x:Key attribute:

<TextBox x:Key="TextBoxKey" /> <!-- Will not compile -->

Answer 3

Yes, you would use x:Key to assign a key to resources inside a ResourceDictionary, either locally in the resources section for an element or a specific ResourceDictionay. This key is then used to look up the resource, through {DynamicResource XXX} or {StaticResource XXX}.

x:Name is used to assign a name to a control in xaml. This can then be used to access the element in the code behind file, using the usual syntax or using an ElementName binding inside the file.