Full RelayCommand in F#? - f#

Question

I am new to F#. As a learning experiment, I am rewriting a C# application in pure F#. How can the "RelayCommand" , RelayCommand, of C# be written in F# ?
Any help is most appreciated.
TIA
As requested, this is the RelayCommand I've been using in C#. :( It seems overly complicated. (There must surely be a simpler one!).
public class RelayCommand<T> : ICommand
{
private readonly WeakAction<T> _execute;
private readonly WeakFunc<T, bool> _canExecute;
public RelayCommand(Action<T> execute)
: this(execute, null)
{
}
public RelayCommand(Action<T> execute, Func<T, bool> canExecute)
{
if (execute == null)
{
throw new ArgumentNullException("execute");
}
_execute = new WeakAction<T>(execute);
if (canExecute != null)
{
_canExecute = new WeakFunc<T, bool>(canExecute);
}
}
public event EventHandler CanExecuteChanged
{
add
{
if (_canExecute != null)
{
CommandManager.RequerySuggested += value;
}
}
remove
{
if (_canExecute != null)
{
CommandManager.RequerySuggested -= value;
}
}
}
public void RaiseCanExecuteChanged()
{
CommandManager.InvalidateRequerySuggested();
}
public bool CanExecute(object parameter)
{
if (_canExecute == null)
{
return true;
}
if (_canExecute.IsStatic || _canExecute.IsAlive)
{
if (parameter == null && typeof(T).IsValueType)
{
return _canExecute.Execute(default(T));
}
if (parameter == null || parameter is T)
{
return (_canExecute.Execute((T)parameter));
}
}
return false;
}
public virtual void Execute(object parameter)
{
var val = parameter;
if (CanExecute(val)
&& _execute != null
&& (_execute.IsStatic || _execute.IsAlive))
{
if (val == null)
{
if (typeof(T).IsValueType)
{
_execute.Execute(default(T));
}
else
{
// ReSharper disable ExpressionIsAlwaysNull
_execute.Execute((T)val);
// ReSharper restore ExpressionIsAlwaysNull
}
}
else
{
_execute.Execute((T)val);
}
}
}
}
public class WeakFunc<TResult>
{
private Func<TResult> _staticFunc;
/// <summary>
/// Gets or sets the <see cref="MethodInfo" /> corresponding to this WeakFunc's
/// method passed in the constructor.
/// </summary>
protected MethodInfo Method
{
get;
set;
}
/// <summary>
/// Get a value indicating whether the WeakFunc is static or not.
/// </summary>
public bool IsStatic
{
get
{
return _staticFunc != null;
}
}
public virtual string MethodName
{
get
{
if (_staticFunc != null)
{
return _staticFunc.Method.Name;
}
return Method.Name;
}
}
protected WeakReference FuncReference
{
get;
set;
}
protected WeakReference Reference
{
get;
set;
}
protected WeakFunc()
{
}
public WeakFunc(Func<TResult> func)
: this(target: func?.Target, func: func)
{
}
public WeakFunc(object target, Func<TResult> func)
{
if (func.Method.IsStatic)
{
_staticFunc = func;
if (target != null)
{
// Keep a reference to the target to control the
// WeakAction's lifetime.
Reference = new WeakReference(target);
}
return;
}
Method = func.Method;
FuncReference = new WeakReference(func.Target);
Reference = new WeakReference(target);
}
public virtual bool IsAlive
{
get
{
if (_staticFunc == null
&& Reference == null)
{
return false;
}
if (_staticFunc != null)
{
if (Reference != null)
{
return Reference.IsAlive;
}
return true;
}
return Reference.IsAlive;
}
}
public object Target
{
get
{
if (Reference == null)
{
return null;
}
return Reference.Target;
}
}
protected object FuncTarget
{
get
{
if (FuncReference == null)
{
return null;
}
return FuncReference.Target;
}
}
public TResult Execute()
{
if (_staticFunc != null)
{
return _staticFunc();
}
var funcTarget = FuncTarget;
if (IsAlive)
{
if (Method != null
&& FuncReference != null
&& funcTarget != null)
{
return (TResult)Method.Invoke(funcTarget, null);
}
}
return default(TResult);
}
public void MarkForDeletion()
{
Reference = null;
FuncReference = null;
Method = null;
_staticFunc = null;
}
}
As a newbie to F#, how can this be implemented? How does F# deal with "WeakAction"?
Thank you.