Custom Section / NameValueSectionHandler in Webconfig

Question

 I have custom section Links which I Should edit from UI. While saving I couldn't save the value of the corresponding key. It shows "collection is read only" error. Please help me to resolve this. Thanks in Advance.

 

WebConfig

<sectionGroup name="Menu">
<section name="Links" type="System.Configuration.NameValueSectionHandler"/>
</sectionGroup>

C#

NameValueCollection nameValueCol = (NameValueCollection)ConfigurationManager.GetSection("Menu/Links");
var Key = "Key";
var Value = "Value";
nameValueCol.Set(Key, Value); // Error: collection is read only

so I tried to remove and add the keys still it shows same error.

nameValueCol.Remove(Key); // Error: collection is read only
nameValueCol.Add(Key, Value);