You are interested in the example at this link: https://learn.microsoft.com/en-us/dotnet/api/system.windows.data.binding.path?view=windowsdesktop-9.0#remarks

This example assumes that:

1. the binding source-object has a "ShoppingCart" property.
2. the object that is set in the "ShoppingCart" property has a "ShippingInfo" property. The "ShippingInfo" property is already a "subproperty" of the source-object.
3. the object that is set in the "ShippingInfo" property has a two-dimensional string indexer. "MailingAddress" and "Street" are not properties, but values ​​for the indexer in the "ShippingInfo" property.