var cellInfo = new DataGridCellInfo(rowToSelect, columnToSelect);

// Option 1 - Quick and easy
var stringContent = "I'm a tooltip";
MyRadDataGrid.ShowTooltip(cellInfo, stringContent);


// Option 2 - For everyone who needs more than just a string.
var customContent = new HorizontalStackLayout();
customContent.Children.Add(new Image{ Source = new FileImageSource{File = "warning.png"}});
customContent.Children.Add(new Label{Text = "I'm a tooltip"});

MyRadDataGrid.ShowTooltip(cellInfo, customContent);