xam.plugin.filepicer throw error

async void OnFilePickClicked(object sender, EventArgs e)
{
try
{
var crossFilePicker = Plugin.FilePicker.CrossFilePicker.Current;////Here I'm getting error. Error mentioned below.
var myResult = await crossFilePicker.PickFile();
if (!string.IsNullOrEmpty(myResult.FileName))
{
foreach (byte b in myResult.DataArray) //Empty array
b.ToString();
}
}
catch (InvalidOperationException ex)
{
ex.ToString(); }
}
Error : This functionality is not implemented in the portable version of this assembly. You should reference the NuGet package from your main application project in order to reference the platform-specific implementation.