// Using generics simplifies the type check A LOT, so this is preferred.
/// <summary>
/// Sets the value of an attached property on this control.
/// </summary>
/// <param name="property">The attached property to set.</param>
/// <param name="value">The new value.</param>
/// <typeparam name="T">
/// The type of the value being assigned.
/// </typeparam>
/// <exception cref="InvalidOperationException">
/// Thrown if the type of <paramref name="value"/> is not assignable to the property's type.
/// </exception>
/// <exception cref="ArgumentException">
/// Thrown if the property has a validation function, and the validation function failed.
/// </exception>
public void SetValue <T>(AttachedProperty property, T value)
{
if (_attachedProperties == null)
{
_attachedProperties = new Dictionary <AttachedProperty, object>();
}
if (!property.PropertyType.IsAssignableFrom(typeof(T)))
{
throw new InvalidOperationException("Property is of the wrong type.");
}
if (typeof(T) == typeof(object))
{
SetValue(property, (object)value);
return;
}
if (property.Validate != null && !property.Validate(value))
{
throw new ArgumentException("Value is not valid for this property.", nameof(value));
}
if (!_attachedProperties.TryGetValue(property, out var oldValue))
{
oldValue = property.DefaultValue;
}
var changed = new AttachedPropertyChangedEventArgs(value, oldValue);
_attachedProperties[property] = value;
property.Changed?.Invoke(this, changed);
}
/// <summary>
/// Gets the value of an attached property on this control.
/// </summary>
/// <param name="property">The attached property to get the value of.</param>
/// <returns>
/// The property's value for this object,
/// or the property's default value if it has not been set on this control yet.
/// </returns>
public object GetValue(AttachedProperty property)
{
if (_attachedProperties == null)
{
return(property.DefaultValue);
}
if (!_attachedProperties.TryGetValue(property, out var value))
{
return(property.DefaultValue);
}
return(value);
}
/// <summary>
/// Sets the value of an attached property on this control.
/// </summary>
/// <remarks>
/// If possible, it is recommended to use <see cref="SetValue{T}"/> instead.
/// </remarks>
/// <param name="property">The attached property to set.</param>
/// <param name="value">The new value.</param>
/// <exception cref="ArgumentNullException">
/// Thrown if the property type is a non-nullable value type, but <paramref name="value"/> is null.
/// </exception>
/// <exception cref="ArgumentException">
/// Thrown if the type of <paramref name="value"/> is not assignable to the property's type.
/// </exception>
/// <exception cref="ArgumentException">
/// Thrown if the property has a validation function, and the validation function failed.
/// </exception>
public void SetValue(AttachedProperty property, object value)
{
if (_attachedProperties == null)
{
_attachedProperties = new Dictionary <AttachedProperty, object>();
}
// Verify that the value can be assigned to the property.
if (value == null)
{
if (property.PropertyType.IsValueType &&
// Nullable<T> actually boxes as null. Keep that in mind.
Nullable.GetUnderlyingType(property.PropertyType) == null)
{
throw new ArgumentNullException(nameof(value),
"Property is a value type, but null was passed as value.");
}
}
else
{
if (!property.PropertyType.IsInstanceOfType(value))
{
throw new ArgumentException("Value is of wrong type for property.", nameof(value));
}
}
if (property.Validate != null && !property.Validate(value))
{
throw new ArgumentException("Value is not valid for this property.", nameof(value));
}
if (!_attachedProperties.TryGetValue(property, out var oldValue))
{
oldValue = property.DefaultValue;
}
var changed = new AttachedPropertyChangedEventArgs(value, oldValue);
_attachedProperties[property] = value;
property.Changed?.Invoke(this, changed);
}
/// <summary>
/// Gets the value of an attached property on this control.
/// </summary>
/// <param name="property">The attached property to get the value of.</param>
/// <typeparam name="T">The type to cast the property value to, for convenience.</typeparam>
/// <returns>
/// The property's value for this object,
/// or the property's default value if it has not been set on this control yet.
/// </returns>
/// <exception cref="InvalidCastException">
/// Thrown if the property value is not of type <typeparamref name="T"/>
/// </exception>
public T GetValue <T>(AttachedProperty property)
{
return((T)GetValue(property));
}