DataContractResolver to return a non-null value for name 'int' and namespace ''.'. .

We are getting one error in adding extra field. 

The InnerException message was 'Error in line 1 position 10969. Element 'schemas.datacontract.org/.../System.Collections.Generic:value' contains data from a type that maps to the name ':int'. The deserializer has no knowledge of any type that maps to this name. Consider changing the implementation of the ResolveName method on your DataContractResolver to return a non-null value for name 'int' and namespace ''.'. .

Note: I am getting All integer fields same error. 

Sample code:

<a:KeyValuePairOfstringanyType>
<b:key>yearyouwanttojoin</b:key>
<b:value i:type="c:int">2018</b:value>
</a:KeyValuePairOfstringanyType>

What is the exact issue here?

Thanks in Advance.