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authorE.Z. Hart <hartez@users.noreply.github.com>2016-12-01 21:15:17 (GMT)
committerStephane Delcroix <stephane@delcroix.org>2016-12-01 21:15:17 (GMT)
commit46c25a2edbf257153d7bb33d2ac3997a3718e3ee (patch)
tree92209a25a152c11af33684c1e1933514ac4c407a /Xamarin.Forms.Core
parent3d85653f270854b4aab82e45e6e58afb760feb85 (diff)
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Don't run Command CanExecute on incorrect inherited binding context type (#572)
* Allow Command CanExecute to recover when run on inherited bindingcontext * Make exception handler more generic * Checking types in Command delegates to avoid exception in the first place * Adding type chekc to other Command constructor * Use nameof for ArgumentNullExceptions * Add unit tests for null parameters, handle value types and Nullable<T>
Diffstat (limited to 'Xamarin.Forms.Core')
-rw-r--r--Xamarin.Forms.Core/Command.cs62
1 files changed, 49 insertions, 13 deletions
diff --git a/Xamarin.Forms.Core/Command.cs b/Xamarin.Forms.Core/Command.cs
index 73ae1b0..d15574c 100644
--- a/Xamarin.Forms.Core/Command.cs
+++ b/Xamarin.Forms.Core/Command.cs
@@ -1,22 +1,59 @@
´╗┐using System;
+using System.Reflection;
using System.Windows.Input;
namespace Xamarin.Forms
{
- public sealed class Command<T> : Command
+ public sealed class Command<T> : Command
{
- public Command(Action<T> execute) : base(o => execute((T)o))
+ public Command(Action<T> execute)
+ : base(o =>
+ {
+ if (IsValidParameter(o))
+ {
+ execute((T)o);
+ }
+ })
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ {
+ throw new ArgumentNullException(nameof(execute));
+ }
}
- public Command(Action<T> execute, Func<T, bool> canExecute) : base(o => execute((T)o), o => canExecute((T)o))
+ public Command(Action<T> execute, Func<T, bool> canExecute)
+ : base(o =>
+ {
+ if (IsValidParameter(o))
+ {
+ execute((T)o);
+ }
+ }, o => IsValidParameter(o) && canExecute((T)o))
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ throw new ArgumentNullException(nameof(execute));
if (canExecute == null)
- throw new ArgumentNullException("canExecute");
+ throw new ArgumentNullException(nameof(canExecute));
+ }
+
+ static bool IsValidParameter(object o)
+ {
+ if (o != null)
+ {
+ // The parameter isn't null, so we don't have to worry whether null is a valid option
+ return o is T;
+ }
+
+ var t = typeof(T);
+
+ // The parameter is null. Is T Nullable?
+ if (Nullable.GetUnderlyingType(t) != null)
+ {
+ return true;
+ }
+
+ // Not a Nullable, if it's a value type then null is not valid
+ return !t.GetTypeInfo().IsValueType;
}
}
@@ -28,7 +65,7 @@ namespace Xamarin.Forms
public Command(Action<object> execute)
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ throw new ArgumentNullException(nameof(execute));
_execute = execute;
}
@@ -36,13 +73,13 @@ namespace Xamarin.Forms
public Command(Action execute) : this(o => execute())
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ throw new ArgumentNullException(nameof(execute));
}
public Command(Action<object> execute, Func<object, bool> canExecute) : this(execute)
{
if (canExecute == null)
- throw new ArgumentNullException("canExecute");
+ throw new ArgumentNullException(nameof(canExecute));
_canExecute = canExecute;
}
@@ -50,9 +87,9 @@ namespace Xamarin.Forms
public Command(Action execute, Func<bool> canExecute) : this(o => execute(), o => canExecute())
{
if (execute == null)
- throw new ArgumentNullException("execute");
+ throw new ArgumentNullException(nameof(execute));
if (canExecute == null)
- throw new ArgumentNullException("canExecute");
+ throw new ArgumentNullException(nameof(canExecute));
}
public bool CanExecute(object parameter)
@@ -73,8 +110,7 @@ namespace Xamarin.Forms
public void ChangeCanExecute()
{
EventHandler changed = CanExecuteChanged;
- if (changed != null)
- changed(this, EventArgs.Empty);
+ changed?.Invoke(this, EventArgs.Empty);
}
}
} \ No newline at end of file