gistfile1.txt

using System;
using AppKit;
using CoreGraphics;
using Foundation;
using System.Runtime.InteropServices;

namespace TestFormatter
{
	[Register ("AppDelegate")]
	public class AppDelegate : NSApplicationDelegate
	{
		public AppDelegate ()
		{
		}

		public override void DidFinishLaunching (NSNotification notification)
		{

		}

		public override void WillTerminate (NSNotification notification)
		{
			// Insert code here to tear down your application
		}
	}

	class NumericFormatter : NSNumberFormatter
	{
		[Export ("isPartialStringValid:proposedSelectedRange:originalString:originalSelectedRange:errorDescription:")]
		public bool IsPartialStringValid (ref NSString partialString, out NSRange proposedSelRange, string origString, NSRange origSelRange, out NSString error)
		{
			proposedSelRange = new NSRange ();
			error = new NSString ();

			if (partialString.Length == 0)
			{
				error = new NSString ("there are no value");
				AppKitFramework.NSBeep ();
				return false;
			}

			int number;
			if (!int.TryParse (partialString, out number))
			{
				error = new NSString ("not number");
				AppKitFramework.NSBeep ();
				return false;
			};

			partialString = (NSString)(partialString + " - Test");

			proposedSelRange = origSelRange;
			return false;
		}

	}

	[Register ("NumericTextField")]
	public class NumericTextField : NSTextField
	{
		// Called when created from unmanaged code
		public NumericTextField (IntPtr handle) : base (handle)
		{
			Initialize ();
		}

		[Export ("init:")]
		public NumericTextField (CGRect rect) : base (rect)
		{
			Initialize ();
		}

		// Called when created directly from a XIB file
		[Export ("initWithCoder:")]
		public NumericTextField (NSCoder coder) : base (coder)
		{
			Initialize ();
		}

		public bool IsValid ()
		{
			return ((NumericFormatter)Formatter).NumberFromString (StringValue) != null;
		}

		void Initialize ()
		{
			Formatter = new NumericFormatter ();
		}
	}
}