System.Configuration.ConfigurationElement.this C# (CSharp) Method

        protected internal Object this[String propertyName] {
            get {
                ConfigurationProperty prop = Properties[propertyName];
                if (prop == null) {
                    prop = Properties[DefaultCollectionPropertyName];
                    if (prop.ProvidedName != propertyName) {
                        return null;
                    }
                }
                return this[prop];
            }
            set {
                Debug.Assert(Properties.Contains(propertyName), "Properties.Contains(propertyName)");
                SetPropertyValue(Properties[propertyName], value, false);// Do not ignore locks!!!
            }
        }