I have this XAML
<MultiBinding StringFormat=" {0}{1}/{2}">
<Binding Path="Text" ElementName="tbxAuthHost" />
<Binding Path="Text" ElementName="tbxAuthWebsiteName" />
<Binding Path="Text" ElementName="tbxAuthServicesAddress" />
</MultiBinding>
When I try change ” {0}{1}/{2}” into “{0}{1}/{2}” so no leading space there and then Visual Studio gives this error:
Error 3 The text ‘{1}/{2}’ is not allowed after the closing ‘}’ of a MarkupExtension expression. Line 116 Position 56.
How I can fix this issue?

You can fix this by putting
{}at the front of the string format.The MSDN Page does a particularly bad job of explaining the format.
If you look at the page on the escape sequence it explains that an opening curly bracket at the beginning denotes a markup extension (e.g. Binding), and
{0}{1}/{2}is not a valid markup extension. It doesn’t explain that not having it as the first character also works.