The keyboard does not automatically disappear when the return key is pressed and may cover or obscure certain parts of the UI. To dismiss the keyboard, send the UIResponder.ResignFirstResponder message to the text field that is currently the first responder.

1. Provide ShouldReturn with a delegate or anonymous method that will call ResignFirstResponder on the field:

this.txtDefault.ShouldReturn += (textField) => {
    textField.ResignFirstResponder();
    return true;
};