{} Escape Sequence / Markup Extension

The escape sequence ({}) is used so that an open brace ({)can be used as a literal character in XAML.

XAML readers typically use the open brace ({) to denote the entry point of a markup extension; however, they first check the next character to determine whether it is a closing brace (}). Only when the two braces ({}) are adjacent, are they considered an escape sequence.

If the escape sequence is encountered, the XAML reader should process the remainder of the string as a string. However, if the escape sequence is applied to a member that has a type converter, the string might undergo type conversion when it is interpreted by a XAML writer.

The escape sequence is not a markup extension and is not backed by a class. However, it is a convention that XAML readers (including custom XAML readers) should respect.

A quotation mark (") cannot be used as an escape sequence in this manner. If you need to set a quotation mark as a property value for a noncontent property, use property element syntax and place the quotation mark as a string inside the property element, or use an XML character entity. For a content property, the quotation mark can be the entire content.

The escape sequence ({}) is frequently required when specifying an XML type that must include a namespace qualifier in a location where a XAML markup extension might appear. This includes the start of a XAML attribute value, and in a markup extension, immediately after an equal sign (=). The following example shows escape sequences for an XML namespace that appears at the start of a XAML attribute value.

<StackPanel Name="stacky">
  <StackPanel.Resources>
    <DataTemplate DataType="{}{http://planetsNS}Planet" >
      <StackPanel Orientation="Horizontal">
        <TextBlock Width="100" Text="{Binding Path=Element[{http://planetsNS}DiameterKM].Value}" />
        <TextBlock Width="100" Text="{Binding Path=Attribute[Name].Value}" />
        <TextBlock Text="{Binding Path=Element[{http://planetsNS}Details].Value}" /> 
      </StackPanel>
    </DataTemplate>
  </StackPanel.Resources>

Reference

Concepts