Called to return the index for an item contained in the data source, or -1, if the item can't be found, or this action isn't currently supported.
Parameters
- item
- The item for which to find the index.
Return Value
The index if possible, or -1
Target Platforms: Android 4.4+, iOS 8+
Development Environments: Visual Studio 2015+, Visual Studio for Mac Preview, Xamarin for Visual Studio 4.2+
