A “Loading...” message while performing a network operation (or other long-running task) looks like this:

To display the overlay, follow these steps:

1. Add this LoadingOverlay class to your project:

    using System;
    using UIKit;
    using CoreGraphics;
   
    public class LoadingOverlay : UIView {
    	// control declarations
    	UIActivityIndicatorView activitySpinner;
    	UILabel loadingLabel;
   
    	public LoadingOverlay (CGRect frame) : base (frame)
    	{
    		// configurable bits
    		BackgroundColor = UIColor.Black;
    		Alpha = 0.75f;
    		AutoresizingMask = UIViewAutoresizing.All;
   
    		nfloat labelHeight = 22;
    		nfloat labelWidth = Frame.Width - 20;
   
    		// derive the center x and y
    		nfloat centerX = Frame.Width / 2;
    		nfloat centerY = Frame.Height / 2;
   
    		// create the activity spinner, center it horizontall and put it 5 points above center x
    		activitySpinner = new UIActivityIndicatorView(UIActivityIndicatorViewStyle.WhiteLarge);
    		activitySpinner.Frame = new CGRect (
    			centerX - (activitySpinner.Frame.Width / 2) ,
    			centerY - activitySpinner.Frame.Height - 20 ,
    			activitySpinner.Frame.Width,
    			activitySpinner.Frame.Height);
    		activitySpinner.AutoresizingMask = UIViewAutoresizing.All;
    		AddSubview (activitySpinner);
    		activitySpinner.StartAnimating ();
   
    		// create and configure the "Loading Data" label
    		loadingLabel = new UILabel(new CGRect (
    			centerX - (labelWidth / 2),
    			centerY + 20 ,
    			labelWidth ,
    			labelHeight
    			));
    		loadingLabel.BackgroundColor = UIColor.Clear;
    		loadingLabel.TextColor = UIColor.White;
    		loadingLabel.Text = "Loading Data...";
    		loadingLabel.TextAlignment = UITextAlignment.Center;
    		loadingLabel.AutoresizingMask = UIViewAutoresizing.All;
    		AddSubview (loadingLabel);
    	}
   
    	/// <summary>
    	/// Fades out the control and then removes it from the super view
    	/// </summary>
    	public void Hide ()
    	{
    		UIView.Animate (
    			0.5, // duration
    			() => { Alpha = 0; },
    			() => { RemoveFromSuperview(); }
    		);
    	}
    }
   

2. Create a field in your class to store a reference to the overlay control:

    LoadingOverlay loadPop;
   

3. Before starting a long-running task, create the overlay and add it to the current view:

    var bounds = UIScreen.MainScreen.Bounds;
   
    // show the loading overlay on the UI thread using the correct orientation sizing
    loadPop = new LoadingOverlay (bounds); // using field from step 2
    View.Add (loadPop);
   

4. When the long-running task is complete, call Hide():

    loadPop.Hide ();
   

Download the DisplayLoadingMessage sample code to see a complete working example.