Error in WCF Service

Question

Hello,

 

I got following error when I called method in wcf service which has  SqlParameter class as Method parameter. :

 

 

Type 'System.Data.SqlTypes.SqlString' with data contract name 'string:http://www.w3.org/2001/XMLSchema' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer. 

 

What type of error is this ? I can't understand. Please give me answer.

 

Thanks