A max length

BookAStar/BookAStar/Behaviors/MaxLengthValidator.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Xamarin.Forms;
+
+namespace BookAStar.Behaviors
+{
+    public class MaxLengthValidator : Behavior<Entry>
+    {
+        public static readonly BindableProperty MaxLengthProperty = BindableProperty.Create("MaxLength", typeof(int), typeof(MaxLengthValidator), 0);
+
+        public int MaxLength
+        {
+            get { return (int)GetValue(MaxLengthProperty); }
+            set { SetValue(MaxLengthProperty, value); }
+        }
+
+        protected override void OnAttachedTo(Entry bindable)
+        {
+            bindable.TextChanged += bindable_TextChanged;
+        }
+
+        private void bindable_TextChanged(object sender, TextChangedEventArgs e)
+        {
+            //if (MaxLength != null && MaxLength.HasValue)
+            if (e.NewTextValue.Length > 0 && e.NewTextValue.Length > MaxLength)
+                ((Entry)sender).Text = e.NewTextValue.Substring(0, MaxLength);
+        }
+
+        protected override void OnDetachingFrom(Entry bindable)
+        {
+            bindable.TextChanged -= bindable_TextChanged;
+            
+        }
+    }
+}