vs2017 ios开发中遇到的问题

try
{
//有时候在并行编程中，通过ui主线程来处理并不能够奏效，这时候需要通过禁用UI线程，这样就不会出错：
var previous = UIApplication.CheckForIllegalCrossThreadCalls;
UIApplication.CheckForIllegalCrossThreadCalls = false;

mainWebView.ViewWithTag(99).RemoveFromSuperview();

UIApplication.CheckForIllegalCrossThreadCalls = previous;

}
catch (Exception ex)
{
//在主线程更新UI操作
InvokeOnMainThread(() => {
mainWebView.ViewWithTag(99).RemoveFromSuperview();
});
}