Jurassic.Library.ObjectInstance.SetPropertyValueIfExists C# (CSharp) Method

        public bool SetPropertyValueIfExists(object key, object value, bool throwOnError)
        {
            // Do not store nulls - null represents a non-existant value.
            value = value ?? Undefined.Value;

            // Retrieve information about the property.
            var property = this.schema.GetPropertyIndexAndAttributes(key);
            if (property.Exists == true)
            {
                // Check if the property is read-only.
                if (property.IsWritable == false)
                {
                    // The property is read-only.
                    if (throwOnError == true)
                        throw new JavaScriptException(this.Engine, ErrorType.TypeError, string.Format("The property '{0}' is read-only.", key));
                    return true;
                }

                if ((property.Attributes & (PropertyAttributes.IsAccessorProperty | PropertyAttributes.IsLengthProperty)) == 0)
                {
                    // The property contains a simple value.  Set the property value.
                    this.propertyValues[property.Index] = value;
                }
                else if (property.IsAccessor == true)
                {
                    // The property contains an accessor function.  Set the property value by calling the accessor.
                    ((PropertyAccessorValue)this.propertyValues[property.Index]).SetValue(this, value);
                }
                else
                {
                    // Otherwise, the property is the "magic" length property.
                    double length = TypeConverter.ToNumber(value);
                    uint lengthUint32 = TypeConverter.ToUint32(length);
                    if (length != (double)lengthUint32)
                        throw new JavaScriptException(this.Engine, ErrorType.RangeError, "Invalid array length");
                    ((ArrayInstance)this).Length = lengthUint32;
                }
                return true;
            }

            // Search the prototype chain for a accessor function.  If one is found, it will
            // prevent the creation of a new property.
            bool propertyExistsInPrototype = false;
            ObjectInstance prototypeObject = this.prototype;
            while (prototypeObject != null)
            {
                property = prototypeObject.schema.GetPropertyIndexAndAttributes(key);
                if (property.Exists == true)
                {
                    if (property.IsAccessor == true)
                    {
                        // The property contains an accessor function.  Set the property value by calling the accessor.
                        ((PropertyAccessorValue)prototypeObject.propertyValues[property.Index]).SetValue(this, value);
                        return true;
                    }
                    propertyExistsInPrototype = true;
                    break;
                }
                prototypeObject = prototypeObject.prototype;
            }

            // If the property exists in the prototype, create a new property.
            if (propertyExistsInPrototype == true)
            {
                AddProperty(key, value, PropertyAttributes.FullAccess, throwOnError);
                return true;
            }

            // The property does not exist.
            return false;
        }